Climate variability and change: Difference between revisions

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Latest revision as of 12:24, 21 August 2025

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{{short description|Change in the statistical distribution of climate elements for an extended period}}

{{for|the human-induced rise in Earth's average temperature and its effects|Climate change}}

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{{Use dmy dates|date=August 2022}}

{{atmospheric sciences}}

[[Image:Vostok-ice-core-petit.png|thumb|right|Variations in CO₂, temperature and dust from the [[Vostok, Antarctica|Vostok]] ice core over the last 400,000 years]]

{{for|current global climate change|Global warming}}

'''Climate variability''' includes all the variations in the climate that last longer than individual weather events, whereas the term '''climate change''' only refers to those variations that persist for a longer period of time, typically decades or more. ''Climate change'' may refer to any time in Earth's history, but the term is now commonly used to describe contemporary climate change, often popularly referred to as global warming. Since the [[Industrial Revolution]], the climate has increasingly been affected by [[Human impact on the environment|human activities]].<ref>{{Cite book|publisher=The National Academies Press |isbn=978-0-309-14588-6 |author1=America's Climate Choices: Panel on Advancing the Science of Climate Change |author2=National Research Council |title=Advancing the Science of Climate Change | ___location=Washington, D.C. |year=2010 |url=http://www.nap.edu/catalog.php?record_id=12782 |quote=(p1) ... there is a strong, credible body of evidence, based on multiple lines of research, documenting that climate is changing and that these changes are in large part caused by human activities. While much remains to be learned, the core phenomenon, scientific questions, and hypotheses have been examined thoroughly and have stood firm in the face of serious scientific debate and careful evaluation of alternative explanations. (pp. 21–22) Some scientific conclusions or theories have been so thoroughly examined and tested, and supported by so many independent observations and results, that their likelihood of subsequently being found to be wrong is vanishingly small. Such conclusions and theories are then regarded as settled facts. This is the case for the conclusions that the Earth system is warming and that much of this warming is very likely due to human activities. |url-status=dead |archive-url=https://web.archive.org/web/20140529161102/http://www.nap.edu/catalog.php?record_id=12782 |archive-date=29 May 2014 }}</ref>

'''Climate change''' refers to the variation in the [[Earth]]'s global [[climate]] or in regional climates over time. It describes changes in the variability or average state of the atmosphere over time scales ranging from decades to millions of years. These changes can be caused by processes internal to the Earth, external forces (e.g. variations in sunlight intensity) or, more recently, human activities.

The [[climate system]] receives nearly all of its energy from the sun and radiates energy to [[outer space]]. The balance of incoming and outgoing energy and the passage of the energy through the climate system is [[Earth's energy budget]]. When the incoming energy is greater than the outgoing energy, Earth's energy budget is positive and the climate system is warming. If more energy goes out, the energy budget is negative and Earth experiences cooling.

In recent usage, especially in the context of [[environmental policy]], the term "climate change" often refers only to changes in modern climate, including the rise in average surface [[temperature]] known as [[global warming]]. In some cases, the term is also used with a presumption of human causation, as in the [[United Nations]] [[UNFCCC|Framework Convention on Climate Change]] (UNFCCC). The UNFCCC uses "climate variability" for non-human caused variations.<ref>http://www.grida.no/climate/ipcc_tar/wg1/518.htm</ref>

The energy moving through Earth's climate system finds expression in weather, varying on geographic scales and time. Long-term averages and variability of weather in a region constitute the region's climate. Such changes can be the result of "internal variability", when natural processes inherent to the various parts of the climate system alter the distribution of energy. Examples include variability in ocean basins such as the [[Pacific decadal oscillation]] and [[Atlantic multidecadal oscillation]]. Climate variability can also result from ''external forcing'', when events outside of the climate system's components produce changes within the system. Examples include changes in solar output and [[volcanism]].

For information on temperature measurements over various periods, and the data sources available, see [[temperature record]]. For attribution of climate change over the past century, see [[attribution of recent climate change]].

Climate variability has consequences for sea level changes, plant life, and mass extinctions; it also affects human societies.

== Climate change factors ==

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Climate changes reflect variations within the Earth's atmosphere, processes in other parts of the Earth such as oceans and [[cryosphere|ice caps]], and the impact of human activity. The external factors that can shape climate are often called [[climate forcing]]s and include such processes as variations in [[solar radiation]], the Earth's [[orbit]], and [[greenhouse gas]] concentrations.

== Terminology ==

=== Variations within the Earth's climate ===

''Climate variability'' is the term to describe variations in the mean state and other characteristics of climate (such as chances or possibility of extreme weather, etc.) "on all spatial and temporal scales beyond that of individual weather events."<!-- {{Sfn|IPCC AR5 WG1 Glossary|2013|p=1451}} puts page in [[:category:Harv and Sfn no-target errors]] --> Some of the variability does not appear to be caused by known systems and occurs at seemingly random times. Such variability is called ''random variability'' or ''noise''. On the other hand, periodic variability occurs relatively regularly and in distinct modes of variability or climate patterns.{{Sfn|Rohli|Vega|2018|p=274}}

Weather is the day-to-day state of the atmosphere, and is a [[chaos|chaotic]] non-linear [[dynamical system]]. On the other hand, ''climate'' &mdash; the average state of weather &mdash; is fairly stable and predictable. Climate includes the average temperature, amount of precipitation, days of sunlight, and other variables that might be measured at any given site. However, there are also changes within the Earth's environment that can affect the climate. According to NASA the average global temperature is currently 14.6C.

The term ''climate change'' is often used to refer specifically to anthropogenic climate change. Anthropogenic climate change is caused by human activity, as opposed to changes in climate that may have resulted as part of Earth's natural processes.<ref name="UNFCCC-1994">{{cite web |date=21 March 1994 |title=The United Nations Framework Convention on Climate Change |url=http://unfccc.int/resource/ccsites/zimbab/conven/text/art01.htm |quote=''Climate change'' means a change of climate which is attributed directly or indirectly to human activity that alters the composition of the global atmosphere and which is in addition to natural climate variability observed over comparable time periods. |access-date=9 October 2018 |archive-date=20 September 2022 |archive-url=https://web.archive.org/web/20220920173907/https://unfccc.int/resource/ccsites/zimbab/conven/text/art01.htm |url-status=live }}</ref> ''Global warming'' became the dominant popular term in 1988, but within scientific journals global warming refers to surface temperature increases while climate change includes global warming and everything else that increasing [[greenhouse gas]] levels affect.<ref name="NASA-2008">{{cite web |title=What's in a Name? Global Warming vs. Climate Change |publisher=NASA |date=December 5, 2008 |url=http://www.nasa.gov/topics/earth/features/climate_by_any_other_name.html |access-date=23 July 2011 |archive-date=9 August 2010 |archive-url=https://web.archive.org/web/20100809221926/http://www.nasa.gov/topics/earth/features/climate_by_any_other_name.html |url-status=live }}</ref>

==== Glaciation ====

[[Image:Glaciertermalp.JPG|left|thumb|300px|Percentage of advancing glaciers in the Alps in the last 80 years]] [[Glacier]]s are recognized as one of the most sensitive indicators of [[climate]] change, advancing substantially during climate cooling (e.g., the [[Little Ice Age]]) and retreating during climate warming on moderate time scales. [[Glacier]]s grow and collapse, both contributing to natural variability and greatly amplifying externally-forced changes. For the last [[century]], however, glaciers have been unable to regenerate enough [[ice]] during the winters to make up for the ice lost during the summer months (see [[Retreat of glaciers since 1850|glacier retreat]]).

A related term, ''climatic change'', was proposed by the [[World Meteorological Organization]] (WMO) in 1966 to encompass all forms of climatic variability on time-scales longer than 10 years, but regardless of cause. During the 1970s, the term climate change replaced climatic change to focus on anthropogenic causes, as it became clear that human activities had a potential to drastically alter the climate.<ref name="Hulme-2016"/> Climate change was incorporated in the title of the [[Intergovernmental Panel on Climate Change]] (IPCC) and the [[UN Framework Convention on Climate Change]] (UNFCCC). Climate change is now used as both a technical description of the process, as well as a noun used to describe the problem.<ref name="Hulme-2016">{{cite journal |last=Hulme |first=Mike |year=2016 |title=Concept of Climate Change, in: The International Encyclopedia of Geography |journal=The International Encyclopedia of Geography |page=1 |publisher=Wiley-Blackwell/Association of American Geographers (AAG) |url=https://www.academia.edu/10358797 |access-date=16 May 2016 |archive-date=29 September 2022 |archive-url=https://web.archive.org/web/20220929201908/https://www.academia.edu/10358797 |url-status=live }}</ref>

The most significant climate processes of the last several million years are the glacial and [[interglacial]] cycles of the present [[ice age]]. Though shaped by [[Milankovitch cycles|orbital variations]], the internal responses involving [[continental]] ice sheets and 130 m sea-level change certainly played a key role in deciding what climate response would be observed in most regions. Other changes, including [[Heinrich event]]s, [[Dansgaard–Oeschger event]]s and the [[Younger Dryas]] show the potential for glacial variations to influence climate even in the absence of specific orbital changes.

==== OceanCauses variability ====

[[Image:Thermohaline circulation.png|thumb|300px|A schematic of modern thermohaline circulation]]

On the scale of decades, climate changes can also result from interaction of the atmosphere and oceans. Many climate fluctuations, the best known being the [[ENSO|El Niño Southern oscillation]] but also including the [[Pacific decadal oscillation]], the [[North Atlantic oscillation]], and the [[Arctic oscillation]], owe their existence at least in part to different ways that heat can be stored in the oceans and move between different reservoirs. On longer time scales ocean processes such as [[thermohaline circulation]] play a key role in redistributing heat, and can dramatically affect climate.

On the broadest scale, the rate at which energy is received from the [[Sun]] and the rate at which it is lost to space determine the [[equilibrium temperature]] and climate of Earth. This energy is distributed around the globe by winds, ocean currents,<ref name="Hsiung-1985">{{cite journal | title=Estimates of Global Oceanic Meridional Heat Transport | first1=Jane | last1=Hsiung | journal=Journal of Physical Oceanography | volume=15 | issue=11 | pages=1405–13 | date=November 1985 | doi=10.1175/1520-0485(1985)015<1405:EOGOMH>2.0.CO;2 | bibcode=1985JPO....15.1405H | doi-access=free }}</ref><ref name="Vallis-2009">{{cite journal | title=Meridional energy transport in the coupled atmosphere–ocean system: scaling and numerical experiments | first1=Geoffrey K. | last1=Vallis | first2=Riccardo | last2=Farneti | s2cid=122384001 | volume=135 | issue=644 | date=October 2009 | pages=1643–60 | journal=Quarterly Journal of the Royal Meteorological Society | doi=10.1002/qj.498 | bibcode=2009QJRMS.135.1643V }}</ref> and other mechanisms to affect the climates of different regions.<ref name="Trenberth-2009">{{cite journal | title=Earth's Global Energy Budget | last1=Trenberth | first1=Kevin E. | last2=Fasullo | first2=John T. | last3=Kiehl | first3=Jeffrey | display-authors=1 | journal=Bulletin of the American Meteorological Society | volume=90 | issue=3 | pages=311–23 | year=2009 | doi=10.1175/2008BAMS2634.1 | bibcode=2009BAMS...90..311T | doi-access=free }}</ref>

==== The memory of climate ====

More generally, most forms of internal variability in the climate system can be recognized as a form of [[hysteresis]], meaning that the current state of climate reflects not only the inputs, but also the history of how it got there. For example, a decade of dry conditions may cause lakes to shrink, plains to dry up and deserts to expand. In turn, these conditions may lead to less rainfall in the following years. In short, climate change can be a self-perpetuating process because different aspects of the environment respond at different rates and in different ways to the fluctuations that inevitably occur.

Factors that can shape climate are called [[climate forcing]]s or "forcing mechanisms".<ref name="Smith-2013">{{cite book |last=Smith |first=Ralph C. |year=2013 |title=Uncertainty Quantification: Theory, Implementation, and Applications |series=Computational Science and Engineering |publisher=SIAM |isbn=978-1611973228 |volume=12 |page=23 |url=https://books.google.com/books?id=Tc1GAgAAQBAJ&pg=PA23}}</ref> These include processes such as variations in [[solar radiation]], variations in the Earth's orbit, variations in the [[albedo]] or reflectivity of the continents, atmosphere, and oceans, [[orogeny|mountain-building]] and [[continental drift]] and changes in [[greenhouse gas]] concentrations. External forcing can be either anthropogenic (e.g. increased emissions of greenhouse gases and dust) or natural (e.g., changes in solar output, the Earth's orbit, volcano eruptions).<ref>{{harvnb|Cronin|2010|pp=17–18}}</ref> There are a variety of [[climate change feedback]]s that can either amplify or diminish the initial forcing. There are also key [[Tipping points in the climate system|thresholds]] which when exceeded can produce rapid or irreversible change.

=== Non-climate factors driving climate change ===

==== Greenhouse gases ====

[[Image:Phanerozoic Carbon Dioxide.png|right|thumb|300px|Carbon dioxide variations during the last 500 million years]]

Some parts of the climate system, such as the oceans and ice caps, respond more slowly in reaction to climate forcings, while others respond more quickly. An example of fast change is the atmospheric cooling after a volcanic eruption, when [[volcanic ash]] reflects sunlight. [[Thermal expansion]] of ocean water after atmospheric warming is slow, and can take thousands of years. A combination is also possible, e.g., sudden loss of [[albedo]] in the Arctic Ocean as sea ice melts, followed by more gradual thermal expansion of the water.

[[Attribution of recent climate change#Scientific literature and opinion|Current studies]] indicate that [[radiative forcing]] by [[greenhouse gas]]es is the primary cause of global warming. Greenhouse gases are also important in understanding Earth's climate history. According to these studies, the [[greenhouse effect]], which is the warming produced as greenhouse gases trap heat, plays a key role in regulating Earth's temperature.

Climate variability can also occur due to internal processes. Internal unforced processes often involve changes in the distribution of energy in the ocean and atmosphere, for instance, changes in the [[thermohaline circulation]].

Over the last 600 million years, [[carbon dioxide]] concentrations have varied from perhaps >5000 [[parts per notation|ppm]] to less than 200 [[parts per notation|ppm]], due primarily to the impact of geological processes and biological innovations. It has been argued by Veizer et al., 1999, that variations in greenhouse gas concentrations over tens of millions of years have not been well correlated to climate change, with plate tectonics perhaps playing a more dominant role. More recently Royer et al. [http://www.nature.com/nature/journal/v446/n7135/full/nature05699.html] have used the CO₂-climate correlation to derive a value for the [[climate sensitivity]]. There are several examples of rapid changes in the concentrations of greenhouse gases in the [[Earth's atmosphere]] that do appear to correlate to strong warming, including the [[Paleocene-Eocene thermal maximum|Paleocene–Eocene thermal maximum]], the [[Permian-Triassic extinction event|Permian–Triassic extinction event]], and the end of the Varangian [[snowball earth]] event.

=== Internal variability ===

During the modern era, the naturally rising [[carbon dioxide]] levels are implicated as the [[attribution of recent climate change|primary cause]] of [[global warming]] since 1950. According to the Intergovernmental Panel on Climate Change (IPCC), 2007, the atmospheric concentration of CO₂ in 2005 was 379ppm³ compared to the pre-industrial levels of 280ppm³ in other words its 0.02% to 0.03% in the atmosphere this has been much higher in the long history of [[earth]].

[[File:1951+ Percent of global area at temperature records - Seasonal comparison - NOAA.svg |thumb |upright=1.35 |There is seasonal variability in how new high temperature records have outpaced new low temperature records.<ref name="NCEI_NOAA-2023">{{cite web |title=Mean Monthly Temperature Records Across the Globe / Timeseries of Global Land and Ocean Areas at Record Levels for October from 1951–2023 |url=https://www.ncei.noaa.gov/access/monitoring/monthly-report/global/202310/supplemental/page-3 |website=NCEI.NOAA.gov |publisher=National Centers for Environmental Information (NCEI) of the National Oceanic and Atmospheric Administration (NOAA)|archive-url=https://web.archive.org/web/20231116185412/https://www.ncei.noaa.gov/access/monitoring/monthly-report/global/202310/supplemental/page-3 |archive-date=16 November 2023 |date=November 2023 |url-status=live}} (change "202310" in URL to see years other than 2023, and months other than 10=October)</ref>]]

Climatic changes due to internal variability sometimes occur in cycles or oscillations. For other types of natural climatic change, we cannot predict when it happens; the change is called ''random'' or ''stochastic''.{{Sfn|Ruddiman|2008|pp=261–62}} From a climate perspective, the weather can be considered random.<ref>{{Cite journal|last=Hasselmann|first=K.|date=1976|title=Stochastic climate models Part I. Theory|journal=Tellus|volume=28|issue=6|pages=473–85|doi=10.1111/j.2153-3490.1976.tb00696.x|issn=2153-3490|bibcode=1976Tell...28..473H}}</ref> If there are little clouds in a particular year, there is an energy imbalance and extra heat can be absorbed by the oceans. Due to [[climate inertia]], this signal can be 'stored' in the ocean and be expressed as variability on longer time scales than the original weather disturbances.<ref>{{Cite journal|last=Liu|first=Zhengyu|s2cid=53953041|date=14 October 2011|title=Dynamics of Interdecadal Climate Variability: A Historical Perspective|journal=Journal of Climate|volume=25|issue=6|pages=1963–95|doi=10.1175/2011JCLI3980.1|issn=0894-8755|doi-access=free}}</ref> If the weather disturbances are completely random, occurring as [[white noise]], the inertia of glaciers or oceans can transform this into climate changes where longer-duration oscillations are also larger oscillations, a phenomenon called [[red noise]].{{Sfn|Ruddiman|2008|p=262}} Many climate changes have a random aspect and a cyclical aspect. This behavior is dubbed ''[[stochastic resonance]]''.{{Sfn|Ruddiman|2008|p=262}} Half of the [[List of Nobel laureates in Physics#Laureates|2021 Nobel prize on physics]] was awarded for this work to [[Klaus Hasselmann]] jointly with [[Syukuro Manabe]] for related work on [[climate model]]ling. While [[Giorgio Parisi]] who with collaborators introduced<ref>{{cite journal|vauthors=Benzi R, Parisi G, Sutera A, Vulpiani A|year=1982|title=Stochastic resonance in climatic change|journal=Tellus|volume=34|issue=1|pages=10–6|bibcode=1982Tell...34...10B|doi=10.1111/j.2153-3490.1982.tb01787.x|url=https://www.openaccessrepository.it/record/123925 |archive-url=https://web.archive.org/web/20241201230816/https://www.openaccessrepository.it/record/123925 |url-status=dead |archive-date=1 December 2024 |url-access=subscription}}</ref> the concept of stochastic resonance was awarded the other half but mainly for work on theoretical physics.

[[Thermodynamics]] and [[Le Chatelier's principle]] explain the characteristics of the dynamic equilibrium of a gas in solution such as the vast amount of C0₂ held in solution in the world's oceans moving into and returning from the atmosphere. These principals can be observed as bubbles which rise in a pot of water heated on a stove, or a in a glass of cold beer allowed to sit at room temperature; gases dissolved in liquids are released under certain circumstances.

==== PlateOcean-atmosphere tectonicsvariability ====

The ocean and atmosphere can work together to spontaneously generate internal climate variability that can persist for years to decades at a time.<ref>{{cite journal |last1=Brown |first1=Patrick T. |last2=Li |first2=Wenhong |last3=Cordero |first3=Eugene C. |last4=Mauget |first4=Steven A. |date=21 April 2015 |title=Comparing the model-simulated global warming signal to observations using empirical estimates of unforced noise |journal=Scientific Reports |issn=2045-2322 |doi=10.1038/srep09957 |pmc=4404682 |pmid=25898351 |volume=5|issue=1 |page=9957 |bibcode=2015NatSR...5.9957B }}</ref><ref>{{cite journal |last=Hasselmann |first=K. |date=1 December 1976 |title=Stochastic climate models Part I. Theory |journal=Tellus |issn=2153-3490 |doi=10.1111/j.2153-3490.1976.tb00696.x |volume=28 |issue=6 |pages=473–85 |bibcode=1976Tell...28..473H }}</ref> These variations can affect global average surface temperature by redistributing heat between the deep ocean and the atmosphere<ref>{{cite journal |last1=Meehl |first1=Gerald A. |last2=Hu |first2=Aixue |last3=Arblaster |first3=Julie M. |last4=Fasullo |first4=John |last5=Trenberth |first5=Kevin E. |s2cid=16183172 |date=8 April 2013 |title=Externally Forced and Internally Generated Decadal Climate Variability Associated with the Interdecadal Pacific Oscillation |journal=Journal of Climate |issn=0894-8755 |doi=10.1175/JCLI-D-12-00548.1 |volume=26 |issue=18 |pages=7298–310 |bibcode=2013JCli...26.7298M |osti=1565088 |url=https://zenodo.org/record/1234599 |access-date=5 June 2020 |archive-date=11 March 2023 |archive-url=https://web.archive.org/web/20230311124210/https://zenodo.org/record/1234599 |url-status=live |doi-access=free }}</ref><ref>{{cite journal |last1=England |first1=Matthew H. |last2=McGregor |first2=Shayne |last3=Spence |first3=Paul |last4=Meehl |first4=Gerald A. |last5=Timmermann |first5=Axel |author-link5= Axel Timmermann |last6=Cai |first6=Wenju |last7=Gupta |first7=Alex Sen |last8=McPhaden |first8=Michael J. |last9=Purich |first9=Ariaan |date=1 March 2014 |title=Recent intensification of wind-driven circulation in the Pacific and the ongoing warming hiatus |journal=Nature Climate Change |issn=1758-678X |doi=10.1038/nclimate2106 |volume=4 |issue=3 |pages=222–27|bibcode=2014NatCC...4..222E |hdl=1959.4/unsworks_13554 |hdl-access=free }}</ref> and/or by altering the cloud/water vapor/sea ice distribution which can affect the total energy budget of the Earth.<ref>{{cite journal |last1=Brown |first1=Patrick T. |last2=Li |first2=Wenhong |last3=Li |first3=Laifang |last4=Ming |first4=Yi |date=28 July 2014 |title=Top-of-atmosphere radiative contribution to unforced decadal global temperature variability in climate models |journal=Geophysical Research Letters |issn=1944-8007 |doi=10.1002/2014GL060625 |volume=41 |issue=14 |page=2014GL060625 |bibcode=2014GeoRL..41.5175B |hdl=10161/9167 |s2cid=16933795 |hdl-access=free }}</ref><ref>{{cite journal |last1=Palmer |first1=M. D. |last2=McNeall |first2=D. J. |date=1 January 2014 |title=Internal variability of Earth's energy budget simulated by CMIP5 climate models |journal=Environmental Research Letters |issn=1748-9326 |doi=10.1088/1748-9326/9/3/034016 |volume=9 |issue=3 |page=034016 |bibcode=2014ERL.....9c4016P |doi-access=free }}</ref>

On the longest time scales, [[plate tectonics]] will reposition [[continent]]s, shape [[ocean]]s, build and tear down [[mountain]]s and generally serve to define the stage upon which climate exists. More recently, plate motions have been implicated in the intensification of the present [[ice age]] when, approximately 3 million years ago, the North and South American plates collided to form the [[Isthmus of Panama]] and shut off direct mixing between the [[Atlantic]] and [[Pacific]] Oceans.

==== Oscillations and cycles {{anchor|Oscillations|Cycles}} ====

==== Solar variation ====

[[File:20210827 Global surface temperature bar chart - bars color-coded by El Niño and La Niña intensity.svg|thumb| upright=1.25|Colored bars show how El Niño years (red, regional warming) and La Niña years (blue, regional cooling) relate to overall [[global surface temperature|global warming]]. The [[El Niño–Southern Oscillation]] has been linked to variability in longer-term global average temperature increase.]]

[[Image:Solar Activity Proxies.png|right|thumb|250px|Variations in solar activity during the last several centuries based on observations of [[sunspot]]s and [[beryllium]] isotopes.]]

A ''climate oscillation'' or ''climate cycle'' is any recurring cyclical [[oscillation]] within global or regional [[climate]]. They are [[quasiperiodic]] (not perfectly periodic), so a [[Fourier analysis]] of the data does not have sharp peaks in the [[spectral density estimation|spectrum]]. Many oscillations on different time-scales have been found or hypothesized:<ref>{{Cite web|url=https://www.whoi.edu/main/topic/el-nino-other-oscillations|title=El Niño & Other Oscillations|website=Woods Hole Oceanographic Institution|access-date=6 April 2019|archive-date=6 April 2019|archive-url=https://web.archive.org/web/20190406082544/https://www.whoi.edu/main/topic/el-nino-other-oscillations|url-status=live}}</ref>

The [[sun]] is the ultimate source of essentially all heat in the climate system. The energy output of the sun, which is converted to heat at the Earth's surface, is an integral part of shaping the Earth's climate. On the longest time scales, the sun itself is getting brighter with higher energy output; as it continues its [[main sequence]], this slow change or evolution affects the Earth's atmosphere. Early in [[History of Earth|Earth's history]], it is thought to have been too cold to support liquid water at the Earth's surface, leading to what is known as the [[Faint young sun paradox]].

* the [[El Niño–Southern Oscillation]] (ENSO) – A large scale pattern of warmer ([[El Niño]]) and colder ([[La Niña]]) tropical [[sea surface temperature]]s in the Pacific Ocean with worldwide effects. It is a self-sustaining oscillation, whose mechanisms are well-studied.<ref>{{Cite journal|last=Wang|first=Chunzai|date=2018|title=A review of ENSO theories|journal=National Science Review|volume=5|issue=6|pages=813–825|doi=10.1093/nsr/nwy104|issn=2095-5138|doi-access=free}}</ref> ENSO is the most prominent known source of inter-annual variability in weather and climate around the world. The cycle occurs every two to seven years, with El Niño lasting nine months to two years within the longer term cycle.<ref>{{cite web|url=http://www.cpc.noaa.gov/products/analysis_monitoring/ensostuff/ensofaq.shtml#HOWOFTEN|title=ENSO FAQ: How often do El Niño and La Niña typically occur?|author=Climate Prediction Center|date=19 December 2005|publisher=[[National Centers for Environmental Prediction]]|url-status=dead|archive-url=https://web.archive.org/web/20090827143632/http://www.cpc.noaa.gov/products/analysis_monitoring/ensostuff/ensofaq.shtml#HOWOFTEN|archive-date=27 August 2009|access-date=26 July 2009|author-link=Climate Prediction Center}}</ref> The cold tongue of the equatorial Pacific Ocean is not warming as fast as the rest of the ocean, due to increased [[upwelling]] of cold waters off the west coast of South America.<ref>{{cite web|url=https://lamont.columbia.edu/news/part-pacific-ocean-not-warming-expected-why|title=Part of the Pacific Ocean Is Not Warming as Expected. Why|author=Kevin Krajick|publisher=Columbia University Lamont-Doherty Earth Observatory|access-date=2 November 2022|archive-date=5 March 2023|archive-url=https://web.archive.org/web/20230305101155/https://lamont.columbia.edu/news/part-pacific-ocean-not-warming-expected-why|url-status=live}}</ref><ref>{{cite web|url=https://www.newsweek.com/mystery-stretch-pacific-ocean-warming-world-1445990?amp=1|title=Mystery Stretch of the Pacific Ocean Is Not Warming Like the Rest of the World's Waters|author=Aristos Georgiou|date=26 June 2019 |publisher=Newsweek|access-date=2 November 2022|archive-date=25 February 2023|archive-url=https://web.archive.org/web/20230225140142/https://www.newsweek.com/mystery-stretch-pacific-ocean-warming-world-1445990?amp=1|url-status=live}}</ref>

On more modern time scales, there are also a variety of forms of [[solar variation]], including the 11-year [[solar cycle]] and longer-term modulations. However, the 11-year sunspot cycle does not manifest itself clearly in the climatological data. Solar intensity variations are considered to have been influential in triggering the [[Little Ice Age]], and for some of the warming observed from 1900 to 1950. The cyclical nature of the sun's energy output is not yet fully understood; it differs from the very slow change that is occurring to the sun as it ages and evolves.

* the [[Madden–Julian oscillation]] (MJO) – An eastward moving pattern of increased rainfall over the tropics with a period of 30 to 60 days, observed mainly over the Indian and Pacific Oceans.<ref>{{Cite web|url=https://www.climate.gov/news-features/blogs/enso/what-mjo-and-why-do-we-care|title=What is the MJO, and why do we care?|website=NOAA Climate.gov|language=en|access-date=6 April 2019|archive-date=15 March 2023|archive-url=https://web.archive.org/web/20230315025156/https://www.climate.gov/news-features/blogs/enso/what-mjo-and-why-do-we-care|url-status=dead}}</ref>

* the [[North Atlantic oscillation]] (NAO) – Indices of the [[North Atlantic oscillation|NAO]] are based on the difference of normalized [[sea-level pressure]] (SLP) between [[Ponta Delgada|Ponta Delgada, Azores]] and [[Stykkishólmur]]/[[Reykjavík]], Iceland. Positive values of the index indicate stronger-than-average westerlies over the middle latitudes.<ref name="NCAR">National Center for Atmospheric Research. [http://www.cgd.ucar.edu/cas/jhurrell/indices.info.html Climate Analysis Section.] {{webarchive|url=https://web.archive.org/web/20060622232926/http://www.cgd.ucar.edu/cas/jhurrell/indices.info.html|date=22 June 2006}} Retrieved on 7 June 2007.</ref>

* the [[Quasi-biennial oscillation]] – a well-understood oscillation in wind patterns in the [[stratosphere]] around the equator. Over a period of 28 months the dominant wind changes from easterly to westerly and back.<ref>{{Cite journal|last1=Baldwin|first1=M. P.|last2=Gray|first2=L. J.|last3=Dunkerton|first3=T. J.|last4=Hamilton|first4=K.|last5=Haynes|first5=P. H.|last6=Randel|first6=W. J.|last7=Holton|first7=J. R.|last8=Alexander|first8=M. J.|last9=Hirota|first9=I.|s2cid=16727059|date=2001|title=The quasi-biennial oscillation|journal=Reviews of Geophysics|language=en|volume=39|issue=2|pages=179–229|doi=10.1029/1999RG000073|bibcode=2001RvGeo..39..179B|doi-access=free}}</ref>

* [[Pacific Centennial Oscillation]] - a [[climate oscillation]] predicted by some [[climate model]]s

* the [[Pacific decadal oscillation]] – The dominant pattern of sea surface variability in the North Pacific on a decadal scale. During a "warm", or "positive", phase, the west Pacific becomes cool and part of the eastern ocean warms; during a "cool" or "negative" phase, the opposite pattern occurs. It is thought not as a single phenomenon, but instead a combination of different physical processes.<ref>{{Cite journal|last1=Newman|first1=Matthew|last2=Alexander|first2=Michael A.|last3=Ault|first3=Toby R.|last4=Cobb|first4=Kim M.|last5=Deser|first5=Clara|last6=Di Lorenzo|first6=Emanuele|last7=Mantua|first7=Nathan J.|last8=Miller|first8=Arthur J.|last9=Minobe|first9=Shoshiro|s2cid=4824093|date=2016|title=The Pacific Decadal Oscillation, Revisited|journal=Journal of Climate|volume=29|issue=12|pages=4399–4427|doi=10.1175/JCLI-D-15-0508.1|issn=0894-8755|bibcode=2016JCli...29.4399N}}</ref>

* the [[Interdecadal Pacific oscillation]] (IPO) – Basin wide variability in the Pacific Ocean with a period between 20 and 30 years.<ref>{{Cite web|url=https://www.niwa.co.nz/node/111124|title=Interdecadal Pacific Oscillation|date=19 January 2016|website=NIWA|language=en|access-date=6 April 2019|archive-date=17 March 2023|archive-url=https://web.archive.org/web/20230317140832/https://niwa.co.nz/node/111124|url-status=live}}</ref>

* the [[Atlantic multidecadal oscillation]] – A pattern of variability in the North Atlantic of about 55 to 70 years, with effects on rainfall, droughts and hurricane frequency and intensity.<ref>{{Cite journal|last1=Kuijpers|first1=Antoon|last2=Bo Holm Jacobsen|last3=Seidenkrantz|first3=Marit-Solveig|last4=Knudsen|first4=Mads Faurschou|date=2011|title=Tracking the Atlantic Multidecadal Oscillation through the last 8,000 years|journal=Nature Communications|language=en|volume=2|issue=1 |pages=178–|doi=10.1038/ncomms1186|pmid=21285956|issn=2041-1723|pmc=3105344|bibcode=2011NatCo...2..178K}}</ref>

* [[North African climate cycles]] – climate variation driven by the [[North African Monsoon]], with a period of tens of thousands of years.<ref>{{cite journal|last1=Skonieczny|first1=C.|date=2 January 2019|title=Monsoon-driven Saharan dust variability over the past 240,000 years|journal=Science Advances|volume=5|issue=1|pages=eaav1887|doi=10.1126/sciadv.aav1887|pmc=6314818|pmid=30613782|bibcode=2019SciA....5.1887S}}</ref>

* the [[Arctic oscillation]] (AO) and [[Antarctic oscillation]] (AAO) – The annular modes are naturally occurring, hemispheric-wide patterns of climate variability. On timescales of weeks to months they explain 20–30% of the variability in their respective hemispheres. The Northern Annular Mode or [[Arctic oscillation]] (AO) in the Northern Hemisphere, and the Southern Annular Mode or [[Antarctic oscillation]] (AAO) in the southern hemisphere. The annular modes have a strong influence on the temperature and precipitation of mid-to-high latitude land masses, such as Europe and Australia, by altering the average paths of storms. The NAO can be considered a regional index of the AO/NAM.<ref>{{cite web |last1=Thompson |first1=David |title=Annular Modes – Introduction |url=https://www.atmos.colostate.edu/~davet/ao/introduction.html |access-date=11 February 2020 |archive-date=18 March 2023 |archive-url=https://web.archive.org/web/20230318094533/https://www.atmos.colostate.edu/~davet/ao/introduction.html |url-status=live }}</ref> They are defined as the first [[Empirical orthogonal functions|EOF]] of sea level pressure or geopotential height from 20°N to 90°N (NAM) or 20°S to 90°S (SAM).

* [[Dansgaard–Oeschger cycles]] – occurring on roughly 1,500-year cycles during the [[Last Glacial Maximum]]

==== OrbitalOcean variationscurrent changes ====

{{See also|Thermohaline circulation}}

In their impact on climate, orbital variations are in some sense an extension of solar variability, because slight variations in the Earth's [[orbit]] lead to changes in the distribution and abundance of sunlight reaching the Earth's surface. Such orbital variations, known as [[Milankovitch cycles]], are a highly predictable consequence of basic physics due to the mutual interactions of the Earth, its moon, and the other planets. These variations are considered the driving factors underlying the glacial and interglacial cycles of the present ice age. Subtler variations are also present, such as the repeated advance and retreat of the [[Sahara]] desert in response to orbital precession.

[[File:Ocean circulation conveyor belt.jpg|thumb|right|upright=1.35|A schematic of modern [[thermohaline circulation]]. Tens of millions of years ago, continental-plate movement formed a land-free gap around Antarctica, allowing the formation of the [[Antarctic Circumpolar Current|ACC]], which keeps warm waters away from Antarctica.]]

The oceanic aspects of climate variability can generate variability on centennial timescales due to the ocean having hundreds of times more mass than in the [[Atmosphere of Earth|atmosphere]], and thus very high [[thermal inertia]]. For example, alterations to ocean processes such as thermohaline circulation play a key role in redistributing heat in the world's oceans.

Ocean currents transport a lot of energy from the warm tropical regions to the colder polar regions. Changes occurring around the last ice age (in technical terms, the last [[glacial period]]) show that the circulation in the [[North Atlantic]] can change suddenly and substantially, leading to global climate changes, even though the total amount of energy coming into the climate system did not change much. These large changes may have come from so called [[Heinrich events]] where internal instability of ice sheets caused huge ice bergs to be released into the ocean. When the ice sheet melts, the resulting water is very low in salt and cold, driving changes in circulation.{{sfn|Burroughs|2001|pp=207–08}}

==== Volcanism ====

A single [[volcano|eruption]] of the kind that occurs several times per century can impact climate, causing cooling for a period of a few years. For example, the eruption of [[Mount Pinatubo]] in 1991 is barely visible on the global temperature profile. Huge eruptions, known as [[large igneous province]]s, occur only a few times every hundred million years, but can reshape climate for millions of years and cause [[mass extinction]]s. Initially, scientists thought that the dust emitted into the atmosphere from large volcanic eruptions was responsible for the cooling by partially blocking the transmission of [[solar radiation]] to the Earth's surface. However, measurements indicate that most of the dust thrown in the atmosphere returns to the Earth's surface within six months.

==== Life ====

Volcanoes are also part of the extended [[carbon cycle]]. Over very long (geological) time periods, they release carbon dioxide from the earth's interior, counteracting the uptake by sedimentary rocks and other geological carbon sinks. However, this contribution is insignificant compared to the current anthropogenic emissions. The [[US Geological Survey]] estimates that human activities generate 150 times the amount of carbon dioxide emitted by volcanoes. [http://volcanoes.usgs.gov/Hazards/What/VolGas/volgas.html]

Life affects climate through its role in the [[carbon cycle|carbon]] and [[water cycle]]s and through such mechanisms as [[albedo]], [[evapotranspiration]], [[Cloud|cloud formation]], and [[weathering]].<ref>{{cite journal |last1=Spracklen |first1=D. V. |last2=Bonn |first2=B. |last3=Carslaw |first3=K. S. |year=2008 |title=Boreal forests, aerosols and the impacts on clouds and climate |journal=Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences |doi=10.1098/rsta.2008.0201 |pmid=18826917 |bibcode=2008RSPTA.366.4613S |volume=366 |issue=1885 |pages=4613–26 |s2cid=206156442 }}</ref><ref>{{cite journal |last1=Christner |first1=B. C. |last2=Morris |first2=C. E. |last3=Foreman |first3=C. M. |last4=Cai |first4=R. |last5=Sands |first5=D. C. |year=2008 |title=Ubiquity of Biological Ice Nucleators in Snowfall |journal=Science |doi=10.1126/science.1149757 |pmid=18309078 |bibcode=2008Sci...319.1214C |volume=319 |issue=5867 |page=1214 |s2cid=39398426 |url=https://scholarworks.montana.edu/xmlui/bitstream/1/13209/1/08-006_Ubiquity_of_biological.pdf |archive-url=https://web.archive.org/web/20200305072355/https://scholarworks.montana.edu/xmlui/bitstream/1/13209/1/08-006_Ubiquity_of_biological.pdf |archive-date=2020-03-05 |url-status=live }}</ref><ref>{{cite journal |last1=Schwartzman |first1=David W. |last2=Volk |first2=Tyler |year=1989 |title=Biotic enhancement of weathering and the habitability of Earth |journal=Nature |bibcode=1989Natur.340..457S |doi=10.1038/340457a0 |volume=340 |issue=6233 |pages=457–60 |s2cid=4314648 }}</ref> Examples of how life may have affected past climate include:

* [[glaciation]] 2.3 billion years ago triggered by the evolution of oxygenic [[photosynthesis]], which depleted the atmosphere of the greenhouse gas carbon dioxide and introduced free oxygen<ref>{{cite journal |doi=10.1073/pnas.0504878102 |title=The Paleoproterozoic snowball Earth: A climate disaster triggered by the evolution of oxygenic photosynthesis |year=2005 |last1=Kopp |first1=R.E. |last2=Kirschvink |first2=J.L. |last3=Hilburn |first3=I.A. |last4=Nash |first4=C.Z. |journal=Proceedings of the National Academy of Sciences |volume=102 |issue=32 |pages=11131–36 |pmid=16061801 |pmc=1183582|bibcode = 2005PNAS..10211131K |doi-access=free }}</ref><ref>{{cite journal |doi=10.1126/science.1071184 |title= Life and the Evolution of Earth's Atmosphere |year=2002 |last1= Kasting |first1=J.F. |journal= Science |volume=296 |issue=5570 |pages= 1066–68 |pmid=12004117 |last2=Siefert |first2=JL|s2cid=37190778 |bibcode = 2002Sci...296.1066K }}</ref>

* another glaciation 300 million years ago ushered in by long-term burial of [[lignin|decomposition-resistant]] [[detritus]] of vascular land-plants (creating a [[carbon sink]] and [[Coal#Formation|forming coal]])<ref>{{cite journal |doi=10.1126/science.271.5252.1105 |title= Middle to Late Paleozoic Atmospheric CO2 Levels from Soil Carbonate and Organic Matter |year=1996 |last1=Mora |first1=C.I. |last2=Driese |first2=S.G. |last3=Colarusso |first3=L. A. |journal=Science |volume=271 |issue=5252 |pages=1105–07 |bibcode= 1996Sci...271.1105M|s2cid=128479221 }}</ref><ref>{{cite journal |doi=10.1073/pnas.96.20.10955 |title=Atmospheric oxygen over Phanerozoic time |year=1999 |last1=Berner |first1=R.A. |journal=Proceedings of the National Academy of Sciences |volume=96 |issue=20 |pages= 10955–57 |pmid=10500106 |pmc=34224|bibcode = 1999PNAS...9610955B |doi-access=free }}</ref>

* termination of the [[Paleocene–Eocene Thermal Maximum]] 55 million years ago by flourishing marine [[phytoplankton]]<ref>{{cite journal |doi=10.1038/35025035 |year=2000 |last1=Bains |first1=Santo |last2=Norris |first2=Richard D. |last3=Corfield |first3=Richard M. |last4=Faul |first4=Kristina L. |journal=Nature |volume=407 |issue=6801 |pages=171–74 |pmid=11001051 |title=Termination of global warmth at the Palaeocene/Eocene boundary through productivity feedback|bibcode = 2000Natur.407..171B |s2cid=4419536 }}</ref><ref name="Zachos-2000">{{cite journal |doi=10.1080/11035890001221188 |title=An assessment of the biogeochemical feedback response to the climatic and chemical perturbations of the LPTM |year= 2000 |last1=Zachos |first1= J.C. |last2= Dickens |first2=G.R. |journal= GFF |volume=122 |issue=1 |pages=188–89|bibcode=2000GFF...122..188Z |s2cid=129797785 }}</ref>

* reversal of global warming 49 million years ago by [[Azolla event|800,000 years of arctic azolla blooms]]<ref>{{cite journal |doi=10.1111/j.1472-4669.2009.00195.x |title=The Eocene Arctic Azolla bloom: Environmental conditions, productivity and carbon drawdown |year=2009 |last1=Speelman |first1=E.N. |last2=Van Kempen |first2=M.M.L. |last3=Barke |first3=J. |last4=Brinkhuis |first4=H. |last5=Reichart |first5=G.J. |last6=Smolders |first6=A.J.P. |last7=Roelofs |first7=J.G.M. |last8=Sangiorgi |first8=F. |last9=De Leeuw |first9=J.W. |last10=Lotter |first10=A.F. |last11=Sinninghe Damsté |first11=J.S. |s2cid=13206343 |journal=Geobiology |volume=7 |issue=2 |pages=155–70 |pmid=19323694|bibcode=2009Gbio....7..155S }}</ref><ref>{{cite journal |doi=10.1038/nature04692 |title=Episodic fresh surface waters in the Eocene Arctic Ocean |year=2006 |last1=Brinkhuis |first1=Henk |last2=Schouten |first2=Stefan |last3=Collinson |first3=Margaret E. |last4=Sluijs |first4=Appy |last5=Sinninghe Damsté |first5=Jaap S. Sinninghe |last6=Dickens |first6=Gerald R. |last7=Huber |first7=Matthew |last8=Cronin |first8=Thomas M. |last9=Onodera |first9=Jonaotaro |last10=Takahashi |first10=Kozo |last11=Bujak |first11=Jonathan P. |last12=Stein |first12=Ruediger |last13=Van Der Burgh |first13=Johan |last14=Eldrett |first14=James S. |last15=Harding |first15=Ian C. |last16=Lotter |first16=André F. |last17=Sangiorgi |first17=Francesca |last18=Van Konijnenburg-Van Cittert |first18=Han van Konijnenburg-van |last19=De Leeuw |first19=Jan W. |last20=Matthiessen |first20=Jens |last21=Backman |first21=Jan |last22=Moran |first22=Kathryn |last23=Expedition 302 |journal=Nature |volume=441 |issue=7093 |pages=606–09 |pmid=16752440 |first23=Scientists|bibcode = 2006Natur.441..606B |hdl=11250/174278 |s2cid=4412107 |hdl-access=free }}</ref>

* global cooling over the past 40 million years driven by the expansion of grass-grazer [[ecosystem]]s<ref>{{cite journal |doi=10.1086/320791 |title=Cenozoic Expansion of Grasslands and Climatic Cooling |year=2001 |last1=Retallack |first1=Gregory J. |s2cid=15560105 |journal=The Journal of Geology |volume=109 |issue=4 |pages=407–26 |bibcode=2001JG....109..407R}}</ref><ref>{{cite journal |doi=10.1130/0091-7613(1997)025<0039:MTPVCA>2.3.CO;2 |title= Miocene to present vegetation changes: A possible piece of the Cenozoic cooling puzzle |year=1997 |last1=Dutton |first1=Jan F. |last2=Barron |first2=Eric J. |journal=Geology |volume=25 |issue= 1 |page=39|bibcode = 1997Geo....25...39D }}</ref>

=== External climate forcing ===

[[Image:Climate Change Attribution.png|thumb|left|[[Attribution of recent climate change]]]]

==== Greenhouse gases ====

=== Human influences on climate change ===

{{Main|Greenhouse gas}}

Anthropogenic factors are acts by humans that change the environment and influence climate. Various theories of human-induced climate change have been debated for many years. In the late 1800s, the [[Rain follows the plow]] theory had many adherents in the western [[United States]].

[[File:Carbon Dioxide 800kyr.svg|thumb|right|upright=1.35|{{CO2}} concentrations over the last 800,000 years as measured from ice cores (blue/green) and directly (black)]]

Whereas [[greenhouse gas]]es released by the biosphere is often seen as a feedback or internal climate process, greenhouse gases emitted from volcanoes are typically classified as external by climatologists.<ref>{{harvnb|Cronin|2010|p=17}}</ref> Greenhouse gases, such as {{CO2}}, methane and [[nitrous oxide]], heat the climate system by trapping infrared light. Volcanoes are also part of the extended [[carbon cycle]]. Over very long (geological) time periods, they release carbon dioxide from the Earth's crust and mantle, counteracting the uptake by sedimentary rocks and other geological [[carbon dioxide sink]]s.

Since the [[Industrial Revolution]], humanity has been adding to greenhouse gases by emitting CO₂ from [[fossil fuel]] combustion, changing [[land use]] through deforestation, and has further altered the climate with [[aerosols]] (particulate matter in the atmosphere),<ref>{{cite web |url=https://www.science.org.au/learning/general-audience/science-booklets-0/science-climate-change/3-are-human-activities-causing |title=3. Are human activities causing climate change? |publisher=Australian Academy of Science |website=science.org.au |access-date=12 August 2017 |archive-date=8 May 2019 |archive-url=https://web.archive.org/web/20190508094624/https://www.science.org.au/learning/general-audience/science-booklets-0/science-climate-change/3-are-human-activities-causing |url-status=live }}</ref> release of trace gases (e.g. nitrogen oxides, carbon monoxide, or methane).<ref>{{cite book

The biggest factor of present concern is the increase in CO₂ levels due to emissions from [[fossil fuel]] combustion, followed by [[particulate|aerosols]] (particulate matter in the atmosphere) which exerts a cooling effect and [[cement]] manufacture. Other factors, including land use, [[ozone depletion]], animal agriculture [http://www.virtualcentre.org/en/library/key_pub/longshad/A0701E00.htm] and deforestation also impact climate.

|title = Climate Change, Human Systems and Policy Volume I

|chapter = Anthropogenic Climate Influences

|editor = Antoaneta Yotova

|date = 2009

|publisher = Eolss Publishers

|isbn = 978-1-905839-02-5

|url = https://www.eolss.net/ebooklib/bookinfo/climate-change-human-systems-policy.aspx

|access-date = 16 August 2020

|archive-date = 4 April 2023

|archive-url = https://web.archive.org/web/20230404081859/http://www.eolss.net/ebooklib/bookinfo/climate-change-human-systems-policy.aspx

|url-status = live

}}</ref> Other factors, including land use, [[ozone depletion]], animal husbandry ([[ruminant]] animals such as [[cattle]] produce [[methane]]<ref name="Steinfeld-2006">{{cite book |last=Steinfeld |first=H. |author2=P. Gerber |author3=T. Wassenaar |author4=V. Castel |author5=M. Rosales |author6=C. de Haan |title=Livestock's long shadow |year=2006 |url=https://www.fao.org/docrep/010/a0701e/a0701e00.HTM |access-date=21 July 2009 |archive-date=26 July 2008 |archive-url=https://web.archive.org/web/20080726214204/http://www.fao.org/docrep/010/a0701e/a0701e00.htm |url-status=live }}</ref>), and [[deforestation]], also play a role.<ref name="NYT-2015">{{cite news |author=The Editorial Board |title=What the Paris Climate Meeting Must Do |url=https://www.nytimes.com/2015/11/29/opinion/sunday/what-the-paris-climate-meeting-must-do.html |date=28 November 2015 |work=[[The New York Times]] |access-date=28 November 2015 |archive-date=29 November 2015 |archive-url=https://web.archive.org/web/20151129034132/http://www.nytimes.com/2015/11/29/opinion/sunday/what-the-paris-climate-meeting-must-do.html |url-status=live }}</ref>

The [[US Geological Survey]] estimates are that volcanic emissions are at a much lower level than the effects of current human activities, which generate 100–300 times the amount of carbon dioxide emitted by volcanoes.<ref>{{cite web|url=http://volcanoes.usgs.gov/Hazards/What/VolGas/volgas.html|title=Volcanic Gases and Their Effects|date=10 January 2006|publisher=U.S. Department of the Interior|access-date=21 January 2008|archive-date=1 August 2013|archive-url=https://web.archive.org/web/20130801120440/http://volcanoes.usgs.govvolcanoes.usgs.gov/|url-status=live}}</ref> The annual amount put out by human activities may be greater than the amount released by [[Supervolcano|supereruptions]], the most recent of which was the [[Toba catastrophe theory|Toba eruption]] in Indonesia 74,000 years ago.<ref name="AGU-2011">{{cite web|url=http://www.agu.org/news/press/pr_archives/2011/2011-22.shtml|title=Human Activities Emit Way More Carbon Dioxide Than Do Volcanoes|date=14 June 2011|publisher=[[American Geophysical Union]]|access-date=20 June 2011|archive-date=9 May 2013|archive-url=https://web.archive.org/web/20130509191429/http://www.agu.org/news/press/pr_archives/2011/2011-22.shtml|url-status=dead}}</ref>

==== Fossil fuels ====

[[Image:Carbon Dioxide 400kyr.png|thumb|250px|right|Carbon dioxide variations over the last 400,000 years, showing a rise since the industrial revolution.]]

Beginning with the [[industrial revolution]] in the [[1850s]] and accelerating ever since, the human consumption of fossil fuels has elevated CO₂ levels from a concentration of ~280 ppm to more than 380 ppm today. These increases are projected to reach more than 560 ppm before the end of the 21st century. It is known that carbon dioxide levels are substantially higher now than at any time in the last 800,000 years [http://news.bbc.co.uk/2/hi/science/nature/5314592.stm] Along with rising [[methane]] levels, these changes are anticipated to cause an increase of 1.4–5.6 °[[Celsius|C]] between 1990 and 2100 (see [[global warming]]).

==== AerosolsOrbital variations ====

[[File:MilankovitchCyclesOrbitandCores.png|thumb|left|upright=1.35|Milankovitch cycles from 800,000 years ago in the past to 800,000 years in the future.]]

Anthropogenic aerosols, particularly sulphate aerosols from fossil fuel combustion, are believed to exert a cooling influence; see graph.<ref>[http://www.grida.no/climate/ipcc_tar/wg1/figspm-3.htm IPCC TAR SPM figure 3]</ref> This, together with natural variability, is believed to account for the relative "plateau" in the graph of 20th century temperatures in the middle of the century.

Slight variations in Earth's motion lead to changes in the seasonal distribution of sunlight reaching the Earth's surface and how it is distributed across the globe. There is very little change to the area-averaged annually averaged sunshine; but there can be strong changes in the geographical and seasonal distribution. The three types of [[Kinematics|kinematic]] change are variations in Earth's [[Orbital eccentricity|eccentricity]], changes in [[axial tilt|the tilt angle of Earth's axis of rotation]], and [[precession]] of Earth's axis. Combined, these produce [[Milankovitch cycles]] which affect climate and are notable for their correlation to [[glacial period|glacial]] and [[interglacial period]]s,<ref name="UniMontana">{{cite web |url=http://www.homepage.montana.edu/~geol445/hyperglac/time1/milankov.htm|archive-url=https://web.archive.org/web/20110716144130/http://www.homepage.montana.edu/~geol445/hyperglac/time1/milankov.htm|archive-date=16 July 2011|title= Milankovitch Cycles and Glaciation|access-date=2 April 2009 |publisher= University of Montana}}</ref> their correlation with the advance and retreat of the [[Sahara]],<ref name="UniMontana"/> and for their [[cyclostratigraphy|appearance]] in the [[geologic record|stratigraphic record]].<ref>{{cite journal |doi=10.1111/j.1365-3121.1989.tb00403.x|title=A Milankovitch scale for Cenomanian time|year=1989|author=Gale, Andrew S. |journal=Terra Nova |volume=1|pages=420–25|issue=5|bibcode=1989TeNov...1..420G}}</ref><ref>{{cite web|title=Same forces as today caused climate changes 1.4 billion years ago|url=http://www.sdu.dk/en/Om_SDU/Fakulteterne/Naturvidenskab/Nyheder/2015_03_10_climate_cycles|website=sdu.dk|publisher=University of Denmark.|url-status=dead|archive-url=https://web.archive.org/web/20150312163250/http://www.sdu.dk/en/Om_SDU/Fakulteterne/Naturvidenskab/Nyheder/2015_03_10_climate_cycles|archive-date=12 March 2015}}</ref>

During the glacial cycles, there was a high correlation between {{CO2}} concentrations and temperatures. Early studies indicated that {{CO2}} concentrations lagged temperatures, but it has become clear that this is not always the case.<ref name="van Nes-2015">{{Cite journal|last1=van Nes|first1=Egbert H.|last2=Scheffer|first2=Marten|last3=Brovkin|first3=Victor|last4=Lenton|first4=Timothy M.|last5=Ye|first5=Hao|last6=Deyle|first6=Ethan|last7=Sugihara|first7=George|date=2015|title=Causal feedbacks in climate change|journal=Nature Climate Change|language=en|volume=5|issue=5|pages=445–48|doi=10.1038/nclimate2568|bibcode=2015NatCC...5..445V|issn=1758-6798}}</ref> When ocean temperatures increase, the [[solubility]] of {{CO2}} decreases so that it is released from the ocean. The exchange of {{CO2}} between the air and the ocean can also be impacted by further aspects of climatic change.<ref>[https://archive.ipcc.ch/publications_and_data/ar4/wg1/en/ch6s6-4.html Box 6.2: What Caused the Low Atmospheric Carbon Dioxide Concentrations During Glacial Times?] {{Webarchive|url=https://web.archive.org/web/20230108231413/https://archive.ipcc.ch/publications_and_data/ar4/wg1/en/ch6s6-4.html |date=8 January 2023 }} in {{Harvnb|IPCC AR4 WG1|2007}} .</ref> These and other self-reinforcing processes allow small changes in Earth's motion to have a large effect on climate.<ref name="van Nes-2015" />

====Cement manufacture====

Cement manufacturing is the third largest cause of man-made carbon dioxide emissions. While fossil fuel combustion and deforestation each produce significantly more carbon dioxide (CO2), cement-making is responsible for approximately 2.5% of total worldwide emissions from industrial sources (energy plus manufacturing sectors).[http://www.cs.ntu.edu.au/homepages/jmitroy/sid101/uncc/fs030.html]

==== LandSolar useoutput ====

[[File:Solar Activity Proxies.png|thumb|right|upright=1.35|Variations in solar activity during the last several centuries based on observations of [[sunspot]]s and [[beryllium]] isotopes. The period of extraordinarily few sunspots in the late 17th century was the [[Maunder minimum]].|alt=]]The [[Sun]] is the predominant source of [[energy]] input to the Earth's [[climate system]]. Other sources include [[Geothermal energy|geothermal]] energy from the Earth's core, tidal energy from the Moon and heat from the decay of radioactive compounds. Both long term variations in solar intensity are known to affect global climate.{{Sfn|Rohli|Vega|2018|p=296}} [[Solar Variation|Solar output varies]] on shorter time scales, including the 11-year [[solar cycle]]<ref>{{cite journal|last1=Willson|first1=Richard C.|last2=Hudson|first2=Hugh S.|year=1991|title=The Sun's luminosity over a complete solar cycle|journal=Nature|volume=351|issue=6321|pages=42–44|bibcode=1991Natur.351...42W|doi=10.1038/351042a0|s2cid=4273483}}</ref> and longer-term [[modulation]]s.<ref>{{Cite journal|last1=Turner|first1=T. Edward|last2=Swindles|first2=Graeme T.|last3=Charman|first3=Dan J.|last4=Langdon|first4=Peter G.|last5=Morris|first5=Paul J.|last6=Booth|first6=Robert K.|last7=Parry|first7=Lauren E.|last8=Nichols|first8=Jonathan E.|date=5 April 2016|title=Solar cycles or random processes? Evaluating solar variability in Holocene climate records|journal=Scientific Reports|language=en|volume=6|issue=1|pages=23961|doi=10.1038/srep23961|pmid=27045989|issn=2045-2322|pmc=4820721}}</ref> Correlation between sunspots and climate and tenuous at best.{{Sfn|Rohli|Vega|2018|p=296}}

Prior to widespread fossil fuel use, humanity's largest impact on local climate is likely to have resulted from [[land use]]. [[Irrigation]], [[deforestation]], and [[agriculture]] fundamentally change the environment. For example, they change the amount of water going into and out of a given ___location. They also may change the local [[albedo]] by influencing the ground cover and altering the amount of sunlight that is absorbed. For example, there is evidence to suggest that the climate of Greece and other Mediterranean countries was permanently changed by widespread deforestation between 700 BC and 1 AD (the wood being used for shipbuilding, construction and fuel), with the result that the modern climate in the region is significantly hotter and drier, and the species of trees that were used for shipbuilding in the ancient world can no longer be found in the area.

[[History of the Earth|Three to four billion years ago]], the Sun emitted only 75% as much power as it does today.<ref name="Ribas-2010">{{Cite conference |last=Ribas |first=Ignasi |conference=IAU Symposium 264 'Solar and Stellar Variability – Impact on Earth and Planets' |title=The Sun and stars as the primary energy input in planetary atmospheres |journal=Proceedings of the International Astronomical Union |volume=264 |pages=3–18 |date=February 2010 |doi=10.1017/S1743921309992298 |bibcode=2010IAUS..264....3R |arxiv=0911.4872}}</ref> If the atmospheric composition had been the same as today, liquid water should not have existed on the Earth's surface. However, there is evidence for the presence of water on the early Earth, in the [[Hadean]]<ref name="Marty-2006">{{cite journal |doi=10.2138/rmg.2006.62.18 |title=Water in the Early Earth |year=2006 |author=Marty, B. |journal=Reviews in Mineralogy and Geochemistry |volume=62 |issue=1 |pages=421–450 |bibcode=2006RvMG...62..421M}}</ref><ref>{{cite journal |doi=10.1126/science.1110873 |title=Zircon Thermometer Reveals Minimum Melting Conditions on Earliest Earth |year=2005 |last1=Watson |first1=E.B. |journal=Science |volume=308 |issue=5723 |pages=841–44 |pmid=15879213 |last2=Harrison |first2=TM|s2cid=11114317 |bibcode=2005Sci...308..841W}}</ref> and [[Archean]]<ref>{{cite journal |doi=10.1130/0091-7613(1994)022<1067:SWIISL>2.3.CO;2 |title=Surface-water influx in shallow-level Archean lode-gold deposits in Western, Australia |year=1994 |last1=Hagemann |first1=Steffen G. |last2=Gebre-Mariam |first2=Musie |last3=Groves |first3=David I. |journal=Geology |volume=22 |issue=12 |page=1067 |bibcode=1994Geo....22.1067H}}</ref><ref name="Marty-2006"/> eons, leading to what is known as the [[faint young Sun paradox]].<ref name="Sagan-1972">{{cite journal | last = Sagan | first = C. | author2 = G. Mullen | title = Earth and Mars: Evolution of Atmospheres and Surface Temperatures | journal = Science | volume = 177 | issue = 4043 | pages = 52–6 | year = 1972 | url = http://www.sciencemag.org/cgi/content/abstract/177/4043/52?ck=nck | bibcode = 1972Sci...177...52S | doi = 10.1126/science.177.4043.52 | pmid = 17756316 | s2cid = 12566286 | access-date = 30 January 2009 | archive-date = 9 August 2010 | archive-url = https://web.archive.org/web/20100809113551/http://www.sciencemag.org/cgi/content/abstract/177/4043/52?ck=nck | url-status = live | url-access = subscription }}</ref> Hypothesized solutions to this paradox include a vastly different atmosphere, with much higher concentrations of greenhouse gases than currently exist.<ref>{{cite journal |doi=10.1126/science.276.5316.1217 |title=The Early Faint Sun Paradox: Organic Shielding of Ultraviolet-Labile Greenhouse Gases |year=1997 |last1=Sagan |first1=C. |journal=Science |volume=276 |issue=5316 |pages=1217–21 |pmid=11536805 |last2=Chyba |first2=C|bibcode = 1997Sci...276.1217S }}</ref> Over the following approximately 4 billion years, the energy output of the Sun increased. Over the next five billion years, the Sun's ultimate death as it becomes a [[red giant]] and then a [[white dwarf]] will have large effects on climate, with the red giant phase possibly ending any life on Earth that survives until that time.<ref name="Schröder-2008">{{citation |last1=Schröder |first1=K.-P. |last2=Connon Smith |first2=Robert |date=2008 |title=Distant future of the Sun and Earth revisited |journal=[[Monthly Notices of the Royal Astronomical Society]] |volume=386 |issue=1 |pages=155–63 |doi=10.1111/j.1365-2966.2008.13022.x |doi-access=free |bibcode=2008MNRAS.386..155S |arxiv=0801.4031 |s2cid=10073988}}</ref>

A controversial hypothesis by [[William Ruddiman]] called the [[early anthropocene]] hypothesis [http://www.realclimate.org/index.php/archives/2005/12/early-anthropocene-hyppothesis/] suggests that the rise of agriculture and the accompanying deforestation led to the increases in carbon dioxide and methane during the period 5000–8000 years ago. These increases, which reversed previous declines, may have been responsible for delaying the onset of the next glacial period, according to Ruddimann's [[overdue-glaciation]] hypothesis.

==== Volcanism ====

In modern times, a 2007 [[Jet Propulsion Laboratory]] study <ref>[http://www.npr.org/templates/story/story.php?storyId=9242114 California Warming Attributed to Growth] by [[Mandalit del Barco]]. ''[[Day to Day]]'', [[National Public Radio]]. 30 Mar 2007.</ref> found that the average temperature of [[California]] has risen about 2 degrees over the past 50 years, with a much higher increase in urban areas. The change was attributed mostly to extensive human development of the landscape.

[[File:Msu 1978-2010.jpg|thumb|left|upright=1.35|In atmospheric temperature from 1979 to 2010, determined by [[Microwave sounding unit|MSU]] [[NASA]] satellites, effects appear from [[aerosols]] released by major volcanic eruptions ([[El&nbsp;Chichón]] and [[Mount Pinatubo|Pinatubo]]). [[El Niño-Southern Oscillation|El&nbsp;Niño]] is a separate event, from ocean variability.]]

The [[Volcano|volcanic eruptions]] considered to be large enough to affect the Earth's climate on a scale of more than 1 year are the ones that inject over 100,000 [[ton]]s of [[sulfur dioxide|SO₂]] into the [[stratosphere]].<ref name="Miles-2004">{{cite journal

| last1 = Miles | first1 = M.G.

| last2 = Grainger | first2 = R.G.

| last3 = Highwood | first3 = E.J.

| title = The significance of volcanic eruption strength and frequency for climate

| journal = Quarterly Journal of the Royal Meteorological Society

| date = 2004

| volume = 130 | pages = 2361–76

| issue = 602

| doi = 10.1256/qj.03.60

| bibcode = 2004QJRMS.130.2361M

| s2cid = 53005926

}}</ref> This is due to the optical properties of SO₂ and sulfate aerosols, which strongly absorb or scatter solar radiation, creating a global layer of [[sulfuric acid]] haze.<ref>{{cite web

| title = Volcanic Gases and Climate Change Overview

| url = http://volcanoes.usgs.gov/hazards/gas/climate.php

| website = usgs.gov

| publisher = USGS

| access-date = 31 July 2014

| archive-date = 29 July 2014

| archive-url = https://web.archive.org/web/20140729142333/http://volcanoes.usgs.gov/hazards/gas/climate.php

| url-status = live

}}</ref> On average, such eruptions occur several times per century, and cause cooling (by partially blocking the transmission of solar radiation to the Earth's surface) for a period of several years. Although volcanoes are technically part of the lithosphere, which itself is part of the climate system, the IPCC explicitly defines volcanism as an external forcing agent.<ref>[https://archive.ipcc.ch/publications_and_data/ar4/syr/en/annexes.html Annexes] {{Webarchive|url=https://web.archive.org/web/20190706041420/https://archive.ipcc.ch/publications_and_data/ar4/syr/en/annexes.html |date=6 July 2019 }}, in {{Harvnb|IPCC AR4 SYR|2008|p=58}}.</ref>

Notable eruptions in the historical records are the [[1991 eruption of Mount Pinatubo]] which lowered global temperatures by about 0.5&nbsp;°C (0.9&nbsp;°F) for up to three years,<ref>{{cite web

==== Livestock ====

|url=http://pubs.usgs.gov/fs/1997/fs113-97/

According to a 2006 United Nations report, livestock is responsible for 18% of the world’s greenhouse gas emissions as measured in CO₂ equivalents. This however includes land usage change, meaning deforestation in order to create grazing land. In the Amazon, 70% of deforestation is to make way for grazing land, so this is the major factor in the 2006 UN FAO report, which was the first agricultural report to include land usage change into the radiative forcing of livestock. In addition to CO₂ emissions, livestock produces 65% of human-induced nitrous oxide (which has 296 times the global warming potential of CO₂) and 37% of human-induced methane (which has 23 times the global warming potential of CO₂)[http://www.virtualcentre.org/en/library/key_pub/longshad/A0701E00.htm].

|title=The Cataclysmic 1991 Eruption of Mount Pinatubo, Philippines

|last=Diggles

|first=Michael

|date=28 February 2005

|work=U.S. Geological Survey Fact Sheet 113-97

|publisher=[[United States Geological Survey]]

|access-date=8 October 2009

|archive-date=25 August 2013

|archive-url=https://web.archive.org/web/20130825233934/http://pubs.usgs.gov/fs/1997/fs113-97/

|url-status=live

}}</ref><ref>{{cite web

| last1 = Diggles

| first1 = Michael

| title = The Cataclysmic 1991 Eruption of Mount Pinatubo, Philippines

| url = http://pubs.usgs.gov/fs/1997/fs113-97/

| website = usgs.gov

| access-date = 31 July 2014

| archive-date = 25 August 2013

| archive-url = https://web.archive.org/web/20130825233934/http://pubs.usgs.gov/fs/1997/fs113-97/

| url-status = live

}}</ref> and the [[1815 eruption of Mount Tambora]] causing the [[Year Without a Summer]].<ref>{{cite journal

|doi=10.1191/0309133303pp379ra

|title=Climatic, environmental and human consequences of the largest known historic eruption: Tambora volcano (Indonesia) 1815

|year=2003

|last1=Oppenheimer|first1=Clive

|journal=Progress in Physical Geography

|volume=27

|pages=230–59

|issue=2

|bibcode=2003PrPG...27..230O

|s2cid=131663534

}}</ref>

At a larger scale—a few times every 50 million to 100 million years—the eruption of [[large igneous province]]s brings large quantities of [[igneous rock]] from the [[mantle (geology)|mantle]] and [[lithosphere]] to the Earth's surface. Carbon dioxide in the rock is then released into the atmosphere.<ref>{{Cite journal|title=Deep Carbon and the Life Cycle of Large Igneous Provinces|last1=Black|first1=Benjamin A.|last2=Gibson|first2=Sally A.|date=2019|journal=Elements|doi=10.2138/gselements.15.5.319|volume=15|issue=5|pages=319–324|doi-access=free|bibcode=2019Eleme..15..319B }}</ref>

== Interplay of factors ==

<ref>{{cite journal

If a certain forcing (for example, solar variation) acts to change the climate, then there may be mechanisms that act to amplify or reduce the effects. These are called [[positive feedback|positive]] and [[negative feedback|negative]] feedbacks. As far as is known, the climate system is generally stable with respect to these feedbacks: positive feedbacks do not "run away". Part of the reason for this is the existence of a powerful negative feedback between temperature and emitted radiation: radiation increases as the fourth power of absolute temperature.

|doi=10.1016/S0012-8252(00)00037-4

|title=Large igneous provinces and mass extinctions

However, a number of important positive feedbacks do exist. The glacial and interglacial cycles of the present ice age provide an important example. It is believed that orbital variations provide the timing for the growth and retreat of ice sheets. However, the ice sheets themselves reflect sunlight back into space and hence promote cooling and their own growth, known as the ice-albedo feedback. Further, falling sea levels and expanding ice decrease plant growth and indirectly lead to declines in carbon dioxide and methane. This leads to further cooling.

|year=2001

|last1=Wignall|first1=P

Similarly, rising temperatures caused, for example, by anthropogenic emissions of greenhouse gases could lead to retreating snow lines, revealing darker ground underneath, and consequently result in more absorption of sunlight.

|journal=Earth-Science Reviews

|volume=53

|issue=1

|pages=1–33

|bibcode=2001ESRv...53....1W

}}</ref> Small eruptions, with injections of less than 0.1&nbsp;Mt of sulfur dioxide into the stratosphere, affect the atmosphere only subtly, as temperature changes are comparable with natural variability. However, because smaller eruptions occur at a much higher frequency, they too significantly affect Earth's atmosphere.<ref name="Miles-2004" /><ref name="Graf-1997">{{cite journal

| last1 = Graf | first1 = H.-F.

| last2 = Feichter | first2 = J.

| last3 = Langmann | first3 = B.

| title = Volcanic sulphur emissions: Estimates of source strength and its contribution to the global sulphate distribution

| journal = Journal of Geophysical Research: Atmospheres

| date = 1997

| volume = 102 | issue = D9

| pages = 10727–38

| doi = 10.1029/96JD03265

| bibcode=1997JGR...10210727G

| hdl = 21.11116/0000-0003-2CBB-A

| hdl-access = free

}}</ref>

==== Plate tectonics ====

Water vapor, methane, and carbon dioxide can also act as significant positive feedbacks, their levels rising in response to a warming trend, thereby accelerating that trend. Water vapor acts strictly as a feedback (excepting small amounts in the stratosphere), unlike the other major greenhouse gases, which can also act as forcings.

{{Main|Plate tectonics}}

Over the course of millions of years, the motion of tectonic plates reconfigures global land and ocean areas and generates topography. This can affect both global and local patterns of climate and atmosphere-ocean circulation.<ref>{{Cite journal| year =1999| title = Paleoaltimetry incorporating atmospheric physics and botanical estimates of paleoclimate| journal = Geological Society of America Bulletin| volume = 111| pages = 497–511| issue = 4 | doi = 10.1130/0016-7606(1999)111<0497:PIAPAB>2.3.CO;2| first4 = K.A.| last2 = Wolfe | first1 = C.E.| last3 = Molnar | first2 = J.A.| first3 = P.| last4 = Emanuel| last1 = Forest|bibcode = 1999GSAB..111..497F | hdl = 1721.1/10809| hdl-access = free}}</ref>

The position of the continents determines the geometry of the oceans and therefore influences patterns of ocean circulation. The locations of the seas are important in controlling the transfer of heat and moisture across the globe, and therefore, in determining global climate. A recent example of tectonic control on ocean circulation is the formation of the [[Isthmus of Panama]] about 5 million years ago, which shut off direct mixing between the [[Atlantic]] and [[Pacific]] Oceans. This strongly affected the [[western boundary current|ocean dynamics]] of what is now the [[Gulf Stream]] and may have led to Northern Hemisphere ice cover.<ref>{{cite web|url=http://earthobservatory.nasa.gov/Newsroom/NewImages/images.php3?img_id=16401 |title=Panama: Isthmus that Changed the World |access-date=1 July 2008 |publisher=[[NASA]] Earth Observatory |url-status=dead |archive-url=https://web.archive.org/web/20070802015424/http://earthobservatory.nasa.gov/Newsroom/NewImages/images.php3?img_id=16401 |archive-date=2 August 2007 }}</ref><ref>{{cite journal |url=http://www.whoi.edu/oceanus/viewArticle.do?id=2508 |title=How the Isthmus of Panama Put Ice in the Arctic |first1=Gerald H. |last1=Haug |first2=Lloyd D. |last2=Keigwin |date=22 March 2004 |journal=Oceanus |volume=42 |issue=2 |publisher=[[Woods Hole Oceanographic Institution]] |access-date=1 October 2013 |archive-date=5 October 2018 |archive-url=https://web.archive.org/web/20181005081528/http://www.whoi.edu/oceanus/viewArticle.do?id=2508 |url-status=live }}</ref> During the [[Carboniferous]] period, about 300 to 360 million years ago, plate tectonics may have triggered large-scale storage of carbon and increased [[wikt:glaciation|glaciation]].<ref>{{cite journal|title=Isotope stratigraphy of the European Carboniferous: proxy signals for ocean chemistry, climate and tectonics|date=30 September 1999|volume=161|issue=1–3|doi=10.1016/S0009-2541(99)00084-4|pages=127–63|first1=Peter |last1=Bruckschen|first2=Susanne |last2=Oesmanna|first3=Ján |last3=Veizer |journal=Chemical Geology|bibcode=1999ChGeo.161..127B}}</ref> Geologic evidence points to a "megamonsoonal" circulation pattern during the time of the [[supercontinent]] [[Pangaea]], and climate modeling suggests that the existence of the supercontinent was conducive to the establishment of monsoons.<ref>{{cite journal|first=Judith T. |last=Parrish|title=Climate of the Supercontinent Pangea|journal=The Journal of Geology|year=1993|volume=101|pages=215–33 |doi=10.1086/648217|issue=2|publisher=The University of Chicago Press|jstor=30081148|bibcode = 1993JG....101..215P |s2cid=128757269}}</ref>

More complex feedbacks involve the possibility of changing circulation patterns in the ocean or atmosphere. For example, a significant concern in the modern case is that melting glacial ice from Greenland will interfere with sinking waters in the North Atlantic and inhibit thermohaline circulation. This could affect the [[Gulf Stream]] and the distribution of heat to [[Europe]] and the east coast of the [[United States]].

The size of continents is also important. Because of the stabilizing effect of the oceans on temperature, yearly temperature variations are generally lower in coastal areas than they are inland. A larger supercontinent will therefore have more area in which climate is strongly seasonal than will several smaller continents or [[island]]s.

Other potential feedbacks are not well understood and may either inhibit or promote warming. For example, it is unclear whether rising temperatures promote or inhibit vegetative growth, which could in turn draw down either more or less carbon dioxide. Similarly, increasing temperatures may lead to either more or less [[cloud]] cover.<ref>http://www.grida.no/climate/ipcc_tar/wg1/271.htm</ref> Since on balance [[cloud cover]] has a strong cooling effect, any change to the abundance of clouds also impacts climate.<ref>For additional discussion of feedbacks relevant to ongoing climate change, see http://www.grida.no/climate/ipcc_tar/wg1/260.htm</ref>

==== Other mechanisms ====

In all, it seems likely that overall climate feedbacks are negative, as systems with overall positive feedback are highly unstable.

It has been postulated that [[ion]]ized particles known as [[cosmic ray]]s could impact cloud cover and thereby the climate. As the sun shields the Earth from these particles, changes in solar activity were hypothesized to influence climate indirectly as well. To test the hypothesis, [[CERN]] designed the [[CLOUD experiment]], which showed the effect of cosmic rays is too weak to influence climate noticeably.<ref>{{Cite web|url=https://www.carbonbrief.org/why-the-sun-is-not-responsible-for-recent-climate-change|title=Explainer: Why the sun is not responsible for recent climate change|last=Hausfather|first=Zeke|date=18 August 2017|website=Carbon Brief|access-date=5 September 2019|archive-date=17 March 2023|archive-url=https://web.archive.org/web/20230317140828/https://www.carbonbrief.org/why-the-sun-is-not-responsible-for-recent-climate-change/|url-status=live}}</ref><ref>{{Cite journal|last=Pierce|first=J. R.|date=2017|title=Cosmic rays, aerosols, clouds, and climate: Recent findings from the CLOUD experiment|journal=Journal of Geophysical Research: Atmospheres|volume=122|issue=15|pages=8051–55|doi=10.1002/2017JD027475|bibcode=2017JGRD..122.8051P|s2cid=125580175 |issn=2169-8996}}</ref>

Evidence exists that the [[Chicxulub crater|Chicxulub asteroid impact]] some 66 million years ago had severely affected the Earth's climate. Large quantities of sulfate aerosols were kicked up into the atmosphere, decreasing global temperatures by up to 26&nbsp;°C and producing sub-freezing temperatures for a period of 3–16 years. The recovery time for this event took more than 30 years.<ref name="Brugger-2017">{{citation

== Monitoring the current status of climate ==

| contribution=Severe environmental effects of Chicxulub impact imply key role in end-Cretaceous mass extinction

Scientists use "Indicator time series" that represent the many aspects of climate and ecosystem status. The time history provides a historical context. Current status of the climate is also monitored with climate indices.<ref>[http://www.arctic.noaa.gov/detect Arctic Change Indicators]</ref><ref>[http://www.beringclimate.noaa.gov Bering Sea Climate and Ecosystem Indicators]</ref><ref>[http://www.arctic.noaa.gov/essay_bond.html How scientists study climate change]: Some important research concepts used by scientists to study climate variations</ref><ref>[http://www.mccip.org.uk/arc/ UK Marine Climate Change Impacts Partnership, Annual Report Card of current knowledge]</ref>

| last1=Brugger | first1=Julia

| last2=Feulner | first2=Georg | last3=Petri | first3=Stefan

| title=19th EGU General Assembly, EGU2017, proceedings from the conference, 23–28 April 2017|___location=Vienna, Austria

| volume=19 | pages=17167 | date=April 2017 | bibcode=2017EGUGA..1917167B | postscript=. }}</ref> The large-scale use of [[nuclear weapon]]s has also been investigated for its impact on the climate. The hypothesis is that soot released by large-scale fires blocks a significant fraction of sunlight for as much as a year, leading to a sharp drop in temperatures for a few years. This possible event is described as [[nuclear winter]].{{sfn|Burroughs|2001|p=232}}

[[Land surface effects on climate|Humans' use of land]] impact how much sunlight the surface reflects and the concentration of dust. Cloud formation is not only influenced by how much water is in the air and the temperature, but also by the amount of [[aerosols]] in the air such as dust.<ref>{{Cite web|url=https://www.chemistryworld.com/news/mineral-dust-plays-key-role-in-cloud-formation-and-chemistry/6157.article|title=Mineral dust plays key role in cloud formation and chemistry|last=Hadlington|first=Simon 9|date=May 2013|website=Chemistry World|access-date=5 September 2019|archive-date=24 October 2022|archive-url=https://web.archive.org/web/20221024053651/https://www.chemistryworld.com/news/mineral-dust-plays-key-role-in-cloud-formation-and-chemistry/6157.article|url-status=live}}</ref> Globally, more dust is available if there are many regions with dry soils, little vegetation and strong winds.<ref>{{Cite journal|last1=Mahowald|first1=Natalie|author-link=Natalie Mahowald|last2=Albani|first2=Samuel|last3=Kok|first3=Jasper F.|last4=Engelstaeder|first4=Sebastian|last5=Scanza|first5=Rachel|last6=Ward|first6=Daniel S.|last7=Flanner|first7=Mark G.|date=1 December 2014|title=The size distribution of desert dust aerosols and its impact on the Earth system|journal=Aeolian Research|volume=15|pages=53–71|bibcode=2014AeoRe..15...53M|doi=10.1016/j.aeolia.2013.09.002|issn=1875-9637|doi-access=free}}</ref>

== Evidence for climatic change ==

{{Unreferenced|section|date=June 2007}}

Evidence for climatic change is taken from a variety of sources that can be used to reconstruct past climates. Most of the evidence is indirect—climatic changes are inferred from changes in indicators that reflect climate, such as vegetation, [[dendrochronology]], [[ice core]]s, [[sea level change]], and [[glacial retreat]].

== Evidence and measurement of climate changes ==

=== Pollen analysis ===

[[Paleoclimatology]] is the study of changes in climate through the entire history of Earth. It uses a variety of [[proxy (climate)|proxy]] methods from the Earth and life sciences to obtain data preserved within things such as rocks, sediments, ice sheets, tree rings, corals, shells, and microfossils. It then uses the records to determine the past states of the Earth's various climate regions and its atmospheric system. Direct measurements give a more complete overview of climate variability.

Also known as [[palynology]], is based on the notion that the geographical distributions of plant species varies due to particular climate requirements, and that these requirements are the same today as they have been in the past ([[Uniformitarianism]]). Each plant species has a distinctively shaped pollen grain, and if these fall into oxygen-free environments (depositional environments), such as peat bogs, they resist decay. Changes in the pollen found in different levels of the bog indicate, by implication, changes in climate.

=== Direct measurements ===

One limitation of this method is the fact that pollen can be transported considerable distances by wind, wildlife and in some cases running water. Certain depositional sites such as mires may also have been effected by humans through peat cutting for fuel. This has to be taken into consideration when interpretation the pollen record.

Climate changes that occurred after the widespread deployment of measuring devices can be observed directly. Reasonably complete global records of surface temperature are available beginning from the mid-late 19th century. Further observations are derived indirectly from historical documents. Satellite cloud and precipitation data has been available since the 1970s.<ref name="New-2001">{{cite journal|last1=New |first1=M. |last2=Todd |first2=M. |last3=Hulme |first3=M |last4=Jones |first4=P. |s2cid=56212756|date=December 2001|title=Review: Precipitation measurements and trends in the twentieth century|journal=International Journal of Climatology|volume=21|issue=15|pages=1889–922|bibcode=2001IJCli..21.1889N|doi=10.1002/joc.680}}</ref>

[[Historical climatology]] is the study of historical changes in climate and their effect on human history and development. The primary sources include written records such as [[sagas]], [[chronicle]]s, [[map]]s and [[local history]] literature as well as pictorial representations such as [[painting]]s, [[drawing]]s and even [[rock art]]. Climate variability in the recent past may be derived from changes in settlement and agricultural patterns.<ref name="Demenocal-2001">{{Cite journal|last1=Demenocal|first1=P.B.|year=2001|title=Cultural Responses to Climate Change During the Late Holocene|url=http://www.ldeo.columbia.edu/~peter/Resources/Publications/deMenocal.2001.pdf|journal=[[Science (journal)|Science]]|volume=292|issue=5517|pages=667–73|bibcode=2001Sci...292..667D|doi=10.1126/science.1059827|pmid=11303088|s2cid=18642937 |access-date=28 August 2015|archive-date=17 December 2008|archive-url=https://web.archive.org/web/20081217162859/http://www.ldeo.columbia.edu/~peter/Resources/Publications/deMenocal.2001.pdf|url-status=dead}}</ref> [[Archaeological]] evidence, [[oral tradition|oral history]] and [[historical documents]] can offer insights into past changes in the climate. Changes in climate have been linked to the rise<ref name="Sindbaek-2007">{{Cite journal|last1=Sindbaek|first1=S.M.|year=2007|title=Networks and nodal points: the emergence of towns in early Viking Age Scandinavia|journal=[[Antiquity (journal)|Antiquity]]|volume=81|issue=311|pages=119–32|doi=10.1017/s0003598x00094886|doi-access=free}}</ref> and the collapse of various civilizations.<ref name="Demenocal-2001" />

=== Beetles ===

Remains of [[beetle]]s are common in freshwater and land sediments. Different species of beetles tend to be found under different climatic conditions. Knowledge of the present climatic range of the different species, and the age of the sediments in which remains are found, allows past climatic conditions to be inferred.{{Fact|date=June 2007}}

===Glacial geologyProxy measurements ===

[[File:Vostok Petit data.svg|thumb|right|upright=1.35|Variations in [[CO2|CO₂]], temperature and dust from the [[Vostok, Antarctica|Vostok]] ice core over the last 450,000 years.]]

Advancing glaciers leave behind moraines and other features that often have datable material in them, recording the time when a glacier advanced and deposited a feature. Similarly, the lack of glacier cover can be identified by the presence of datable soil or volcanic tephra horizons. Glaciers are considered one of the most sensitive climate indicators by the [[IPCC]], and their recent observed variations provide a global signal of climate change. See [[Retreat of glaciers since 1850]].

Various archives of past climate are present in rocks, trees and fossils. From these archives, indirect measures of climate, so-called proxies, can be derived. Quantification of climatological variation of precipitation in prior centuries and epochs is less complete but approximated using proxies such as marine sediments, ice cores, cave stalagmites, and tree rings.<ref>{{cite journal|last1=Dominic |first1=F. |last2=Burns |first2=S.J. |last3=Neff |first3=U. |last4=Mudulsee |first4=M. |last5=Mangina |first5=A |last6=Matter |first6=A. |date=April 2004 |title=Palaeoclimatic interpretation of high-resolution oxygen isotope profiles derived from annually laminated speleothems from Southern Oman|journal=Quaternary Science Reviews |volume=23 |issue=7–8 |pages=935–45 |bibcode=2004QSRv...23..935F |doi=10.1016/j.quascirev.2003.06.019}}</ref> Stress, too little precipitation or unsuitable temperatures, can alter the growth rate of trees, which allows scientists to infer climate trends by analyzing the growth rate of tree rings. This branch of science studying this called [[dendroclimatology]].<ref>{{Cite book|url=https://books.google.com/books?id=e9Ez2dRGmioC|title=Dendroclimatology: progress and prospect|publisher=Springer Science & Business Media|year=2010|isbn=978-1-4020-4010-8|editor1-last=Hughes|editor1-first=Malcolm K.|series=Developments in Paleoenvironmental Research|volume=11|___location=New York|editor2-last=Swetnam|editor2-first=Thomas W.|editor3-last=Diaz|editor3-first=Henry F.}}</ref> Glaciers leave behind [[moraine]]s that contain a wealth of material—including organic matter, quartz, and potassium that may be dated—recording the periods in which a glacier advanced and retreated.

Analysis of ice in cores drilled from an [[ice sheet]] such as the [[Antarctic ice sheet]], can be used to show a link between temperature and global sea level variations. The air trapped in bubbles in the ice can also reveal the CO₂ variations of the atmosphere from the distant past, well before modern environmental influences. The study of these ice cores has been a significant indicator of the changes in CO₂ over many millennia, and continues to provide valuable information about the differences between ancient and modern atmospheric conditions. The ¹⁸O/¹⁶O ratio in calcite and ice core samples [[Oxygen isotope ratio cycle|used to deduce ocean temperature in the distant past]] is an example of a temperature proxy method.

=== Historical records ===

Historical records include cave paintings, depth of grave digging in [[Greenland]], diaries, documentary evidence of events (such as '[[frost fairs]]' on the [[Thames]]) and evidence of areas of vine cultivation. Daily weather reports have been kept since 1873, and the [[Royal Society]] has encouraged the collection of data since the seventeenth century. Parish records are often a good source of climate data.

The remnants of plants, and specifically pollen, are also used to study climatic change. Plant distributions vary under different climate conditions. Different groups of plants have pollen with distinctive shapes and surface textures, and since the outer surface of pollen is composed of a very resilient material, they resist decay. Changes in the type of pollen found in different layers of sediment indicate changes in plant communities. These changes are often a sign of a changing climate.<ref>{{cite journal|last1=Langdon|first1=P.G.|last2=Barber|first2=K.E.|last3=Lomas-Clarke|first3=S.H.|last4=Lomas-Clarke|first4=S.H.|date=August 2004|title=Reconstructing climate and environmental change in northern England through chironomid and pollen analyses: evidence from Talkin Tarn, Cumbria|journal=Journal of Paleolimnology|volume=32|issue=2|pages=197–213|bibcode=2004JPall..32..197L|doi=10.1023/B:JOPL.0000029433.85764.a5|s2cid=128561705}}</ref><ref>{{cite journal|last=Birks|first=H.H.|date=March 2003|title=The importance of plant macrofossils in the reconstruction of Lateglacial vegetation and climate: examples from Scotland, western Norway, and Minnesota, US|url=https://bora.uib.no/bitstream/1956/387/4/1956-387.pdf|journal=Quaternary Science Reviews|volume=22|issue=5–7|pages=453–73|bibcode=2003QSRv...22..453B|doi=10.1016/S0277-3791(02)00248-2|hdl=1956/387|hdl-access=free|access-date=20 April 2018|archive-date=11 June 2007|archive-url=https://web.archive.org/web/20070611133600/https://bora.uib.no/bitstream/1956/387/4/1956-387.pdf|url-status=dead}}</ref> As an example, pollen studies have been used to track changing vegetation patterns throughout the [[Quaternary glaciation]]s<ref>{{cite journal|last1=Miyoshi|first1=N|last2=Fujiki|first2=Toshiyuki|last3=Morita|first3=Yoshimune|year=1999|title=Palynology of a 250-m core from Lake Biwa: a 430,000-year record of glacial–interglacial vegetation change in Japan|journal=Review of Palaeobotany and Palynology|volume=104|issue=3–4|pages=267–83|doi=10.1016/S0034-6667(98)00058-X|bibcode=1999RPaPa.104..267M}}</ref> and especially since the [[last glacial maximum]].<ref>{{cite journal|last=Prentice|first=I. Colin|author2=Bartlein, Patrick J|author3=Webb, Thompson|year=1991|title=Vegetation and Climate Change in Eastern North America Since the Last Glacial Maximum|journal=Ecology|volume=72|issue=6|pages=2038–56|doi=10.2307/1941558|jstor=1941558|bibcode=1991Ecol...72.2038P }}</ref> Remains of [[beetle]]s are common in freshwater and land sediments. Different species of beetles tend to be found under different climatic conditions. Given the extensive lineage of beetles whose genetic makeup has not altered significantly over the millennia, knowledge of the present climatic range of the different species, and the age of the sediments in which remains are found, past climatic conditions may be inferred.<ref name="Coope-1999">{{cite journal |last1=Coope |first1=G.R. |last2=Lemdahl |first2=G. |last3=Lowe |first3=J.J. |last4=Walkling |first4=A. |date=4 May 1999 |title=Temperature gradients in northern Europe during the last glacial – Holocene transition (14–9 14 C kyr BP) interpreted from coleopteran assemblages |journal=[[Journal of Quaternary Science]] |volume=13 |issue=5 |pages=419–33 |bibcode=1998JQS....13..419C |doi=10.1002/(SICI)1099-1417(1998090)13:5<419::AID-JQS410>3.0.CO;2-D}}</ref>

== Examples of climate change ==

Climate change has continued throughout the entire history of Earth. The field of [[paleoclimatology]] has provided information of climate change in the ancient past, supplementing modern observations of climate.

=== Analysis and uncertainties ===

#Climate of the deep past

One difficulty in detecting climate cycles is that the Earth's climate has been changing in non-cyclic ways over most paleoclimatological timescales. Currently we are in a period of [[Human impact on the environment|anthropogenic]] [[global warming]]. In a larger timeframe, the Earth is [[Holocene glacial retreat|emerging]] from the latest ice age, cooling from the [[Holocene climatic optimum]] and warming from the "[[Little Ice Age]]", which means that climate has been constantly changing over the last 15,000 years or so. During warm periods, temperature fluctuations are often of a lesser amplitude. The [[Pleistocene]] period, dominated by repeated [[glaciation]]s, developed out of more stable conditions in the [[Miocene]] and [[Pliocene climate]]. Holocene climate has been relatively stable. All of these changes complicate the task of looking for cyclical behavior in the climate.

#*[[Faint young sun paradox]]

#*[[Snowball earth]]

#*[[Oxygen Catastrophe]]

#Climate of the last 500 million years

#*[[:Image:Phanerozoic Climate Change.png|Phanerozoic overview]]

#*[[Paleocene-Eocene Thermal Maximum|Paleocene–Eocene Thermal Maximum]]

#*[[Cretaceous Thermal Maximum]]

#*[[Permo-Carboniferous Glaciation|Permo–Carboniferous Glaciation]]

#*[[Ice age]]s

#Climate of recent glaciations

#*[[Dansgaard-Oeschger event|Dansgaard–Oeschger event]]

#*[[Younger Dryas]]

#*[[:Image:Ice Age Temperature.png|Ice age temperatures]]

#Recent climate

#*[[Holocene Climatic Optimum]]

#*[[Medieval Warm Period]]

#*[[Little Ice Age]]

#*[[Year Without a Summer]]

#*[[Temperature record of the past 1000 years]]

#*[[Global warming]]

#*[[Hardiness Zone Migration]]

[[Positive feedback]], [[negative feedback]], and [[ecological inertia]] from the land-ocean-atmosphere system often attenuate or reverse smaller effects, whether from orbital forcings, solar variations or changes in concentrations of greenhouse gases. Certain feedbacks involving processes such as clouds are also uncertain; for [[contrail]]s, natural [[Cirrus cloud|cirrus]] clouds, oceanic [[dimethyl sulfide]] and a land-based equivalent, competing theories exist concerning effects on climatic temperatures, for example contrasting the [[Iris hypothesis]] and [[CLAW hypothesis]].

==Climate change and economics==

{{Main|Economics of global warming}}

There has been a debate about how climate change could affect the [[world economy]]. An [[October 29]], [[2006]] report by former [[World Bank Chief Economist|Chief Economist]] and Senior Vice-President of the [[World Bank]] [[Nicholas Stern]] states that climate change could affect [[Economic growth|growth]], which could be cut by one-fifth unless drastic action is taken. [http://news.bbc.co.uk/1/hi/business/6096594.stm (''Report's stark warning on climate'')]

== Impacts ==

Political advisor [[Frank Luntz]] recommended the [[George W. Bush Administration|Bush Administration]] adopt the term "Climate Change" in preference to [[global warming]], while it worked to discredit the idea of global warming science.

=== Life ===

*[http://en.wikipedia.org/w/index.php?title=Image:High_and_Dry_by_Guy_Pearse.JPG&oldid=143442553 High and Dry: John Howard, climate change and the selling of Australia’s future by Guy Pearse]

[[File:Aridity ice age vs early holocene vs modern.jpg|thumb|upright=1.35|right|''Top:'' [[Arid]] ice age climate{{Clear}}''Middle:'' [[Atlantic period|Atlantic Period]], warm and wet{{Clear}}''Bottom:'' Potential vegetation in climate now if not for human effects like agriculture.<ref name="OakRidge-1997">{{cite web | editor1-last=Adams | editor1-first=J.M. | editor2-last=Faure | editor2-first=H. | year=1997 | url=http://www.esd.ornl.gov/projects/qen/nerc.html | title=Global land environments since the last interglacial | publisher=Oak Ridge National Laboratory | ___location=Tennessee | url-status=dead | archive-url=https://web.archive.org/web/20080116122058/http://www.esd.ornl.gov/projects/qen/nerc.html | archive-date=16 January 2008 | df=dmy-all }} QEN members.</ref>]]

==== Vegetation ====

==Climate change in popular culture==

A change in the type, distribution and coverage of vegetation may occur given a change in the climate. Some changes in climate may result in increased precipitation and warmth, resulting in improved plant growth and the subsequent sequestration of airborne CO₂. Though an increase in CO₂ may benefit plants, some factors can diminish this increase. If there is an environmental change such as drought, increased CO₂ concentrations will not benefit the plant.<ref>{{Cite journal |last=Swann |first=Abigail L. S. |date=2018-06-01 |title=Plants and Drought in a Changing Climate |url=https://doi.org/10.1007/s40641-018-0097-y |journal=Current Climate Change Reports |language=en |volume=4 |issue=2 |pages=192–201 |doi=10.1007/s40641-018-0097-y |bibcode=2018CCCR....4..192S |issn=2198-6061|url-access=subscription }}</ref> So even though climate change does increase CO₂ emissions, plants will often not use this increase as other environmental stresses put pressure on them.<ref>{{Cite journal |last1=Ainsworth |first1=E. A. |last2=Lemonnier |first2=P. |last3=Wedow |first3=J. M. |date=January 2020 |editor-last=Tausz-Posch |editor-first=S. |title=The influence of rising tropospheric carbon dioxide and ozone on plant productivity |journal=Plant Biology |language=en |volume=22 |issue=S1 |pages=5–11 |doi=10.1111/plb.12973 |issn=1435-8603 |pmc=6916594 |pmid=30734441|bibcode=2020PlBio..22S...5A }}</ref> However, sequestration of CO₂ is expected to affect the rate of many natural cycles like [[plant litter]] decomposition rates.<ref>{{cite journal |last1=Ochoa-Hueso |first1=R |last2=Delgado-Baquerizo |first2=N |last3=King |first3=PTA |last4=Benham |first4=M |last5=Arca |first5=V |last6=Power |first6=SA |title=Ecosystem type and resource quality are more important than global change drivers in regulating early stages of litter decomposition |journal=Soil Biology and Biochemistry |date=2019 |volume=129 |pages=144–52 |doi=10.1016/j.soilbio.2018.11.009 |bibcode=2019SBiBi.129..144O |hdl=10261/336676 |s2cid=92606851 |hdl-access=free }}</ref> A gradual increase in warmth in a region will lead to earlier flowering and fruiting times, driving a change in the timing of life cycles of dependent organisms. Conversely, cold will cause plant bio-cycles to lag.<ref>{{cite web |last=Kinver |first=Mark |date=15 November 2011 |title=UK trees' fruit ripening '18 days earlier' |publisher=Bbc.co.uk |url=https://www.bbc.co.uk/news/science-environment-15721263 |access-date=1 November 2012 |archive-date=17 March 2023 |archive-url=https://web.archive.org/web/20230317140816/https://www.bbc.co.uk/news/science-environment-15721263 |url-status=live }}</ref>

{{main|Climate change in popular culture}}

The issue of climate change has entered popular culture since the late [[20th century]]. Science historian [[Naomi Oreskes]] has noted that "there's a huge disconnect between what professional scientists have studied and learned in the last 30 years, and what is out there in the popular culture".[http://seattletimes.nwsource.com/html/nationworld/2002549346_globewarm11.html] An academic study contrasts the relatively rapid acceptance of ozone depletion as reflected in popular culture with the much slower acceptance of the scientific consensus on global warming.[http://pus.sagepub.com/cgi/content/abstract/9/3/297]

Larger, faster or more radical changes, however, may result in vegetation stress, rapid plant loss and [[desertification]] in certain circumstances.<ref name="Sahney-2010">{{cite journal |last1=Sahney |first1=S. |last2=Benton |first2=M.J. |last3=Falcon-Lang |first3=H.J. |year=2010 |title=Rainforest collapse triggered Pennsylvanian tetrapod diversification in Euramerica |journal=Geology |doi=10.1130/G31182.1 |bibcode=2010Geo....38.1079S |volume=38 |issue=12 |pages=1079–82 |url=https://www.academia.edu/368820 |format=PDF |access-date=27 November 2013 |archive-date=17 March 2023 |archive-url=https://web.archive.org/web/20230317140814/https://www.academia.edu/368820 |url-status=live }}</ref><ref>{{cite journal |last1=Bachelet |first1=D. |author-link1=Dominique Bachelet|last2=Neilson |first2=R. |last3=Lenihan |first3=J. M. |last4=Drapek |first4=R.J. |year=2001 |title=Climate Change Effects on Vegetation Distribution and Carbon Budget in the United States |journal=[[Ecosystems]] |doi=10.1007/s10021-001-0002-7 |volume=4 |issue=3 |pages=164–85 |bibcode=2001Ecosy...4..164B |s2cid=15526358 }}</ref><ref>{{Cite journal |last1=Ridolfi |first1=Luca |last2=D'Odorico |first2=P. |last3=Porporato |first3=A. |last4=Rodriguez-Iturbe |first4=I. |date=2000-07-27 |title=Impact of climate variability on the vegetation water stress |url=https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2000JD900206 |journal=Journal of Geophysical Research: Atmospheres |language=en |volume=105 |issue=D14 |pages=18013–18025 |doi=10.1029/2000JD900206 |bibcode=2000JGR...10518013R |issn=0148-0227}}</ref> An example of this occurred during the [[Carboniferous Rainforest Collapse]] (CRC), an extinction event 300 million years ago. At this time vast rainforests covered the equatorial region of Europe and America. Climate change devastated these tropical rainforests, abruptly fragmenting the habitat into isolated 'islands' and causing the extinction of many plant and animal species.<ref name="Sahney-2010" />

==Climate Change and biodiversity==

Some of the most immediate effects of recent climate change are becoming apparent through impacts on [[biodiversity]]. The life cycles of many wild plants and animals are closely linked to the passing of the seasons; climatic changes can lead to interdependent pairs of species (e.g. a wild flower and its pollinating insect) losing synchronisation, if, for example, one has a cycle dependent on day length and the other on temperature or precipitation. In principle, at least, this could lead to extinctions or changes in the distribution and abundance of species.

One phenomenon is the movement of species northwards in Europe. A recent study by [[Butterfly Conservation]] in the UK, [http://www.butterfly-conservation.org/conservation/sobb/sobb2007summary.pdf], has shown that relative common species with a southerly distribution have moved north, whilst scarce upland species have become rarer and lost territory towards the south. This picture has been mirrored across several invertebrate groups.

Drier summers could lead to more periods of drought<ref>[http://www.lilith-ezine.com/articles/environmental/Australian-Drought.html Australian Drought and Climate Change], retrieved on June 7th 2007.</ref>, potentially affecting many species of animal and plant. For example, in the UK during the drought year of 2006 significant numbers of trees dies or showed dieback on light sandy soils. Wetter, milder winters might impact on temperate mammals or insects by preventing them hibernating or entering torpor during periods when food is scarce.

One predicted change is the ascendance of 'weedy' or opportunistic species at the expense of scarcer species with narrower or more specialised ecological requirements. One example could be the expanses of [[bluebells|bluebell]] seen in many woodlands in the UK. These have an early growing and flowering season before competing weeds can develop and the tree canopy closes. Milder winters can allow weeds to overwinter as adult plants or germinate sooner, whilst trees leaf earlier, reducing the length of the window for bluebells to complete their life cycle.

Organisations such as [[Wildlife Trusts|Wildlife Trust]], [[World Wide Fund for Nature]], [[Birdlife International]] and the [[Audubon Society]] are actively monitoring and research the effects of climate change on biodiversity. They also advance policies in areas such as [[landscape scale conservation]] to promote [[adaptation]] to climate change.

A more detailed review of these issues can be found here [http://www.unep-wcmc.org/climate/home.htm]

==== See alsoWildlife ====

One of the most important ways animals can deal with climatic change is migration to warmer or colder regions.{{Sfn|Burroughs|2007|p=273}} On a longer timescale, evolution makes ecosystems including animals better adapted to a new climate.<ref>{{Cite journal|last1=Millington|first1=Rebecca|last2=Cox|first2=Peter M.|last3=Moore|first3=Jonathan R.|last4=Yvon-Durocher|first4=Gabriel|date=10 May 2019|title=Modelling ecosystem adaptation and dangerous rates of global warming|journal=Emerging Topics in Life Sciences|language=en|volume=3|issue=2|pages=221–31|doi=10.1042/ETLS20180113|pmid=33523155|issn=2397-8554|hdl=10871/36988|s2cid=150221323|hdl-access=free}}</ref> Rapid or large climate change can cause [[mass extinctions]] when creatures are stretched too far to be able to adapt.{{Sfn|Burroughs|2007|p=267}}

{{Portal|Energy}}

{{Portal|Ecology}}

==== Humanity ====

{|

Collapses of past civilizations such as the [[Maya civilization|Maya]] may be related to cycles of precipitation, especially drought, that in this example also correlates to the [[Western Hemisphere Warm Pool]]. Around 70 000 years ago the [[Toba Volcano|Toba supervolcano]] eruption created an especially cold period during the ice age, leading to a possible [[Toba bottleneck|genetic bottleneck]] in human populations.

|- valign=top

| width=250 align=left |

* [[Abrupt climate change]]

* [[Alternative propulsion]]

* [[Avoiding Dangerous Climate Change]]

* [[Carbonfund]]

* [[Climate change response]]

* [[Climate Change Science Program]]

* [[Climate model]]

* [[Climate of Mars]]

* [[Economics of global warming]]

* [[Effects of global warming]]

* [[Emission standard]]

* [[Energie-Cités]]

* [[Environmental Change Network]] (ECN)

* [[Fuel efficiency]]

=== Changes in the cryosphere ===

| width=250 align=left |

==== Glaciers and ice sheets ====

* [[Global dimming]]

[[Glacier]]s are considered among the most sensitive indicators of a changing climate.<ref name="Seiz-2007">{{cite report|last=Seiz |first=G. |author2=N. Foppa |title=The activities of the World Glacier Monitoring Service (WGMS) |year=2007 |url=http://www.meteoswiss.admin.ch/web/en/climate/climate_international/gcos/inventory/wgms.Par.0008.DownloadFile.tmp/gcosreportwgmse.pdf |access-date=21 June 2009 |url-status=dead |archive-url=https://web.archive.org/web/20090325100331/http://www.meteoswiss.admin.ch/web/en/climate/climate_international/gcos/inventory/wgms.Par.0008.DownloadFile.tmp/gcosreportwgmse.pdf |archive-date=25 March 2009 }}</ref> Their size is determined by a [[mass balance]] between snow input and melt output. As temperatures increase, glaciers retreat unless snow precipitation increases to make up for the additional melt. Glaciers grow and shrink due both to natural variability and external forcings. Variability in temperature, precipitation and hydrology can strongly determine the evolution of a glacier in a particular season.

* [[Global Observation Research Initiative in Alpine Environments]]

* [[Global Warming]]

* [[Global warming controversy]]

* [[Green vehicle]]

* [[Intergovernmental Panel on Climate Change]]

* [[International Environmental Law]]

* [[Iron fertilization]]

* [[Kyoto Protocol]]

* [[Low-carbon economy]] and [[decarbonisation]]

* [[Millennium Ecosystem Assessment]]

* [[Mitigation of global warming]]

The most significant climate processes since the middle to late [[Pliocene]] (approximately 3 million years ago) are the glacial and [[interglacial]] cycles. The present interglacial period (the [[Holocene]]) has lasted about 11,700 years.<ref name="ICS-2008">{{cite web|url=http://www.stratigraphy.org/column.php?id=Chart/Time%20Scale|title=International Stratigraphic Chart|year=2008|publisher=International Commission on Stratigraphy|access-date=3 October 2011|url-status=dead|archive-url=https://web.archive.org/web/20111015042711/http://www.stratigraphy.org/column.php?id=Chart%2FTime%20Scale|archive-date=15 October 2011}}</ref> Shaped by [[Milankovitch cycles|orbital variations]], responses such as the rise and fall of [[Continental climate|continental]] ice sheets and significant sea-level changes helped create the climate. Other changes, including [[Heinrich event]]s, [[Dansgaard–Oeschger event]]s and the [[Younger Dryas]], however, illustrate how glacial variations may also influence climate without the [[orbital forcing]].

| width=250 align=left |

==== Sea level change ====

* [[Permafrost]]

During the [[Last Glacial Maximum]], some 25,000 years ago, sea levels were roughly 130 m lower than today. The deglaciation afterwards was characterized by rapid sea level change.{{Sfn|Burroughs|2007|p=279}} In the early [[Pliocene]], global temperatures were 1–2˚C warmer than the present temperature, yet sea level was 15–25 meters higher than today.<ref>{{cite web|url=http://www.giss.nasa.gov/research/briefs/hansen_15/|archive-url=https://web.archive.org/web/20110724050602/http://www.giss.nasa.gov/research/briefs/hansen_15/|url-status=dead|archive-date=24 July 2011|title=Science Briefs: Earth's Climate History|last=Hansen|first=James|publisher=NASA GISS|access-date=25 April 2013}}</ref>

* [[Renewable energy]]

* [[Sea level rise]]

* [[Timeline of environmental events]]

* [[Western Regional Climate Action Initiative]]

|}

==== Sea ice ====

{{Wikinewscat|Climate change}}

[[Sea ice]] plays an important role in Earth's climate as it affects the total amount of sunlight that is reflected away from the Earth.<ref>{{Cite journal|last1=Belt|first1=Simon T.|last2=Cabedo-Sanz|first2=Patricia|last3=Smik|first3=Lukas|last4=Navarro-Rodriguez|first4=Alba|last5=Berben|first5=Sarah M. P.|last6=Knies|first6=Jochen|last7=Husum|first7=Katrine|display-authors=3|date=2015|title=Identification of paleo Arctic winter sea ice limits and the marginal ice zone: Optimised biomarker-based reconstructions of late Quaternary Arctic sea ice|journal=Earth and Planetary Science Letters|volume=431|pages=127–39|doi=10.1016/j.epsl.2015.09.020|bibcode=2015E&PSL.431..127B|issn=0012-821X|hdl=10026.1/4335|hdl-access=free}}</ref> In the past, the Earth's oceans have been almost entirely covered by sea ice on a number of occasions, when the Earth was in a so-called [[Snowball Earth]] state,<ref>{{Cite journal|last1=Warren|first1=Stephen G.|last2=Voigt|first2=Aiko|last3=Tziperman|first3=Eli|last4=Sadler|first4=Peter M.|last5=Rose|first5=Catherine V.|last6=Rose|first6=Brian E. J.|last7=Ramstein|first7=Gilles|last8=Partin|first8=Camille A.|last9=Maloof|first9=Adam C.|display-authors=3|date=1 November 2017|title=Snowball Earth climate dynamics and Cryogenian geology-geobiology|journal=Science Advances|volume=3|issue=11|pages=e1600983|doi=10.1126/sciadv.1600983|pmid=29134193|issn=2375-2548|pmc=5677351|bibcode=2017SciA....3E0983H}}</ref> and completely ice-free in periods of warm climate.<ref>{{Cite journal|last1=Caballero|first1=R.|last2=Huber|first2=M.|date=2013|title=State-dependent climate sensitivity in past warm climates and its implications for future climate projections|journal=Proceedings of the National Academy of Sciences|volume=110|issue=35|pages=14162–67|doi=10.1073/pnas.1303365110|pmid=23918397|pmc=3761583|bibcode=2013PNAS..11014162C|issn=0027-8424|doi-access=free}}</ref> When there is a lot of sea ice present globally, especially in the tropics and subtropics, the climate is [[Climate sensitivity|more sensitive to forcings]] as the [[ice–albedo feedback]] is very strong.<ref>{{Cite journal|last1=Hansen James|last2=Sato Makiko|last3=Russell Gary|last4=Kharecha Pushker|date=2013|title=Climate sensitivity, sea level and atmospheric carbon dioxide|journal=Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences|volume=371|issue=2001|pages=20120294|doi=10.1098/rsta.2012.0294|pmc=3785813|pmid=24043864|arxiv=1211.4846|bibcode=2013RSPTA.37120294H}}</ref>

== Climate history ==

{{See also|List of periods and events in climate history|Paleoclimatology}}

Various [[climate forcing]]s are typically in flux throughout [[geologic time]], and some processes of the Earth's temperature may be [[homeostasis|self-regulating]]. For example, during the [[Snowball Earth]] period, large glacial ice sheets spanned to Earth's equator, covering nearly its entire surface, and very high [[albedo]] created extremely low temperatures, while the accumulation of snow and ice likely removed carbon dioxide through [[Deposition (chemistry)|atmospheric deposition]]. However, the absence of [[plant cover]] to absorb atmospheric CO₂ emitted by volcanoes meant that the greenhouse gas could accumulate in the atmosphere. There was also an absence of exposed silicate rocks, which use CO₂ when they undergo weathering. This created a warming that later melted the ice and brought Earth's temperature back up.

=== Paleo-eocene thermal maximum ===

Heat Vaporization of Liquid Gasoline or Petrol fuel as a means to increase vehicle fuel mileage and decrease engine emissions,

[[File:65 Myr Climate Change.png|thumb|upright=1.35|right|Climate changes over the past 65 million years, using proxy data including [[Oxygen-18]] ratios from [[foraminifera]].]]

The [[Paleocene–Eocene Thermal Maximum]] (PETM) was a time period with more than 5–8&nbsp;°C global average temperature rise across the event.<ref name="McInherney-2011">{{cite journal|author=McInherney, F.A..|author2=Wing, S.|year=2011|title=A perturbation of carbon cycle, climate, and biosphere with implications for the future|url=http://www.whoi.edu/fileserver.do?id=136084&pt=2&p=148709|journal=Annual Review of Earth and Planetary Sciences|volume=39|issue=1 |pages=489–516|bibcode=2011AREPS..39..489M|doi=10.1146/annurev-earth-040610-133431|access-date=26 October 2019|archive-date=14 September 2016|archive-url=https://web.archive.org/web/20160914003526/http://www.whoi.edu/fileserver.do?id=136084&pt=2&p=148709|url-status=live|url-access=subscription}}</ref> This climate event occurred at the time boundary of the [[Paleocene]] and [[Eocene]] geological [[Epoch (geology)|epochs]].<ref name="Evans-2008">{{cite journal|author=Westerhold, T..|author2=Röhl, U.|author3=Raffi, I.|author4=Fornaciari, E.|author5=Monechi, S.|author6=Reale, V.|author7=Bowles, J.|author8=Evans, H. F.|year=2008|title=Astronomical calibration of the Paleocene time|url=https://www.geo.arizona.edu/~reiners/fortransfer6/WesterholdEtAl_PPP2008.pdf |archive-url=https://web.archive.org/web/20170809094938/http://www.geo.arizona.edu/~reiners/fortransfer6/WesterholdEtAl_PPP2008.pdf |archive-date=2017-08-09 |url-status=live|journal=Palaeogeography, Palaeoclimatology, Palaeoecology|volume=257|issue=4|pages=377–403|bibcode=2008PPP...257..377W|doi=10.1016/j.palaeo.2007.09.016}}</ref> During the event large amounts of [[methane]] was released, a potent greenhouse gas.{{Sfn|Burroughs|2007|p=|pp=190–91}} The PETM represents a "case study" for modern climate change as in the greenhouse gases were released in a geologically relatively short amount of time.<ref name="McInherney-2011"/> During the PETM, a mass extinction of organisms in the deep ocean took place.<ref>{{Cite journal|last1=Ivany|first1=Linda C.|last2=Pietsch|first2=Carlie|last3=Handley|first3=John C.|last4=Lockwood|first4=Rowan|last5=Allmon|first5=Warren D.|last6=Sessa|first6=Jocelyn A.|date=1 September 2018|title=Little lasting impact of the Paleocene-Eocene Thermal Maximum on shallow marine molluscan faunas|journal=Science Advances|language=en|volume=4|issue=9|pages=eaat5528|doi=10.1126/sciadv.aat5528|issn=2375-2548|pmid=30191179|pmc=6124918|bibcode=2018SciA....4.5528I}}</ref>

=== The Cenozoic ===

For complete info visit, www.byronwine.com/files/1992%20vapor.pdf

Throughout the [[Cenozoic]], multiple climate forcings led to warming and cooling of the atmosphere, which led to the early formation of the [[Antarctic ice sheet]], subsequent melting, and its later reglaciation. The temperature changes occurred somewhat suddenly, at carbon dioxide concentrations of about 600–760 ppm and temperatures approximately 4&nbsp;°C warmer than today. During the Pleistocene, cycles of glaciations and interglacials occurred on cycles of roughly 100,000&nbsp;years, but may stay longer within an interglacial when [[orbital eccentricity]] approaches zero, as during the current interglacial. Previous interglacials such as the [[Eemian interglacial|Eemian]] phase created temperatures higher than today, higher sea levels, and some partial melting of the [[West Antarctic ice sheet]].

By Frieda Mind

Climatological temperatures substantially affect cloud cover and precipitation. At lower temperatures, air can hold less water vapour, which can lead to decreased precipitation.<ref>{{Cite journal|last1=Haerter|first1=Jan O.|last2=Moseley|first2=Christopher|last3=Berg|first3=Peter|date=2013|title=Strong increase in convective precipitation in response to higher temperatures|journal=Nature Geoscience|volume=6|issue=3|pages=181–85|doi=10.1038/ngeo1731|bibcode=2013NatGe...6..181B|issn=1752-0908}}</ref> During the [[Last Glacial Maximum]] of 18,000 years ago, thermal-driven [[evaporation]] from the oceans onto continental landmasses was low, causing large areas of extreme desert, including [[polar desert]]s (cold but with low rates of cloud cover and precipitation).<ref name="OakRidge-1997" /> In contrast, the world's climate was cloudier and wetter than today near the start of the warm [[Atlantic period|Atlantic Period]] of 8000 years ago.<ref name="OakRidge-1997" />

The intended purpose of this project was to more thoroughly utilize gasoline when burning in a spark ignited (SI) internal combustion engine (ICE). Gasoline SI engines have continually been getting further refinements and tuning yet one thing is the same today as 100 years ago. Either if by carburetor or an electronic fuel injection system, the gasoline is introduced to the engine’s intake stroke at relatively the same temperature as it was 100 years ago. Today’s cars have catalytic converters and smog control devices to re-burn most the unburned fuel remaining in car’s exhaust. Wouldn’t it be better if, an engine used that extra fuel and increased its work by burning the fuel properly the first time? There have been people over the past 100 years who have pointed out this problem and offered solutions. The most notably might be Charles Pogue who was issued US patent# 2,026,798 in 1936 for his fuel saving invention.

With conventional SI fuel systems only the gasoline with the opportunity to vaporize by splashing onto a hot piston head, valve or other sizzling engine part prior to being ignited by the spark plug, will be of any help in doing work for the engines power stroke. Any residual fuel vaporized by the flash of burning fuel might also assist the power stroke but it would need to happen quickly and remaining oxygen is scarce and much hotter and less effective.

This project involved studying the works and patents of Pogue along with, Ray Covey’s (Patent# 4,368,163), Loren and Kelly Naylor, The Carb Research Center of Foyil Oklahoma, Harold Schwartz, Robert Shelton, Ivor Newberry, Forrest Gerrard and others.

The works in this paper involved studying principals of vaporizing gasoline to a vaporous state then burning the vaporized gasoline fuel in an SI engine, followed up with a narrative on utilizing these principals with our current available technologies.

Utilizing waste heat from an engine to preheat the gasoline fuel to a vapor prior to introducing to the engine is beneficial in causing the engine to achieve more efficient gas mileage while cleaning up tailpipe emissions. Burning propane in SI powered vehicles has proven to lengthen the engine life, run cooler, and lessen buildup of carbon and sludge. Vapor will also cut down on unburned gasoline from splashing onto oil cylinder walls and causing increased engine wear.

This description explains a fairly complete method to heat gasoline to a highly gassiest state of individual gasoline molecules. It will also describe a method for introducing the gasoline vapor into the engine as fuel via a spray bar or duel fuel mixer. Both these methods are found on vehicles with propane or liquefied petroleum (LP) gas fuel systems.

The vaporized fuel can also be introduced by fuel injection when using vapor-fuel type fuel injectors in conjunction with a computer and a small number of sensors for data input and actuators to maintain a proper fuel heat range and intake air flow.

The narrative describes a method to utilize the engines hot exhaust stream to heat up the gasoline or petrol to the mentioned gassiest state.

Propane turns from a liquid to a vapor at -44F degrees or above unless under pressure. At 100F degrees propane will exert 172 pounds per Square inch (PSI) on the walls of whatever container it is in. Todays gasoline does not vaporize fully till it is heated to over 200F degrees. When using vaporized gasoline as a fuel, the engines hot exhaust is used to heat the fuel to the point of becoming a vapor. Visually inspecting this highly explosive gasoline vapor vented from an untapped nozzle, it has the identical appearance of propane or butane vapor when venting, as in situations of refilling a propane tank.

For aid in understanding how this system works refer to the labeled diagrams and photos. This projects particular system was built for and tested on a Nissan/Datsun 1600cc overhead cam engine as found in late 1960s early 1970s Datsun series. This system will work on any gasoline internal combustion engine and considerably well in certain hybrid electric configurations.

How exhaust is used to vaporize the gasoline,

This narrative will start with the route of the hot exhaust flowing from the engines’ exhaust ports. Right after exiting the engines manifold exhaust ports the exhaust meets a junction with two separate directions to flow. One direction is its usual flow out the exhaust system. The other direction diverts the exhaust flow past a coil of stainless steel (SS) tubing. This (SS) coil is a heat exchanger inserted directly in route of hot exhaust flow. This stainless steel heat exchanger creates turbulence in the exhaust flow much like a muffler. The exhaust is forced to flow around and through this restrictive mass and transfer heat to the (SS) heat exchanger. The gasoline pumped into this very same (SS) coil is pushed through the tubing and forced under low pressure to exit the other end of the tubing in a vaporous state.

The outer mild steel body of this heat exchanger/exhaust manifold can be built from modifying a steel tube exhaust manifold (racing header type) used in race cars and seen in drawing (A). Directly downstream from where exhaust header is bolted to engine head each individual pipe of header has a passage pipe drilled, fitted and welded to it. On a 4 cylinder engine there would be 4 pipes and 4 of these passages or crossovers from each pipe. A six cylinder engine would have a header with 6 pipes and 6 shorter cross over pipes. These crossover pipes lead from the individual header pipes to the sidewall of a larger pipe that is positioned perpendicular and alongside each of the mentioned header pipes. This larger pipe called the heat exchanger housing pipe, can be made from a length of pipe such as a section of exhaust pipe used on large trucks and buses. The pipe in the pictures has an inside diameter of 3 and quarter (3.25)inches. This housing pipe has positioned within it a coiled stainless steel heat exchanger (photo D) that is securely fastened in place to a faceplate by flared tubing fittings. The wall on other end of heat exchanger housing pipe has welded to it a centered positioning pin. The positioning pin is to give the (SS) heat exchanger coil a place to rest against when coil is inserted into housing pipe and faceplate is bolted in place. The faceplate works as a sealed lid and it has machined bolts positioned around its perimeter for secure bolting. The face plate and the housing flange are sealed by either a solid flange gasket or by using a mix of extreme high temperature engine sealant that is thickened with tiny scrapes of ceramic insulation.

The entire manifold assembly is wrapped in high temperature ceramic insulation covered with a heat reflective woven material. This type of material is used in ship engine rooms and other industrial applications.

Prior to pumping fuel into the heat exchanger tubing, the flared fittings (in photo) that secure the (SS) coil to the inside of housing faceplate are tested for leaks. On the outlet end of the stainless steel coil is located a well insulated surge chamber. This small surge chamber is used to accommodate and store a small amount of hot vapor to be available for supplying short bursts of power on demand in quick acceleration situations.

Fitted and also welded onto heat exchanger housing pipe in addition to crossover pipes is an exit pipe. This extra pipe (seen in photo with hose clamp around it) is the same size (or larger) to that of the engines stock exhaust pipe. This pipe provides a route for the hot exhaust gases to exit the heat exchanger after heating the (SS) coil. The exhaust continues out the heat exchangers exit pipe and continues to run under the car and out the back.

When the exhaust stream exits the engines exhaust ports and follows the conventional route out the original header pipes (avoiding the mentioned heat exchanger) these header pipes will converge into a larger junction pipe. Located within this larger pipe at this conversion ___location is a ‘gate’ for closing off the exhaust flow (or not). This gate can be actuated by, electronics, hydraulics, pneumatics, mechanical, telepathic or cable means, to open or close the flow of exhaust passing through the header convergence pipe. Closing this gate has the effect of forcing most the hot exhaust into the heat exchanger where it can do work to bring up the temperature of the incoming gasoline contained within the coil of stainless steel (SS) fuel line. The volume and temperature of exhaust passing through the heat exchanger dictates available fuel vapor heating capacity.

Beyond the gate the two divergent exhaust streams can continue out the back of the vehicle as separate pipes or can re-converge into one pipe after the gate then exit out the vehicles rear.

Regulating a proper heat range,

Regulating temperature is critical for keeping incoming gasoline heated to proper ranges. When vehicle idles it uses less fuel and also generates less heat, running under a load is opposite more fuel needed and more available heat. Ample heat to the fuel is provided under most operating conditions but problem arises when operating in varying and crowded traffic conditions when it becomes difficult to regulate the temperatures quick enough to compensate for the varied range of engine RPMs in stop and go driving. The insulated surge chamber with a responsive manifold gate can make this type of driving a possibility for vehicles with a traditional drive train, but it is difficult to design this type of system for stop and go driving conditions. A true hybrid electric/ICE system with a well designed and responsive vaporized gasoline carburetion system would be more practical. The best systems would be an ICE coupled to a battery bank to generate electricity, and a large electric motor to drive the car and regenerate power when braking. A more advanced hybrid design that would work very well with this type of vapor fuel technology would be one like the Toyota hybrid electric system.

A Hybrid Electric system designed so regenerative braking and propulsion using an electric motor drawing power from a small battery bank recharged by, or charged directly from either a diesel or a vapor fuel injected gasoline powered engine. This type of system would allow the gasoline SI engine to provide power to recharge the batteries and assist with power on hills and loads. It will also allow the engine to operate within a closer power RPM range. With less variations in engine RPMs it becomes simpler to adjust the exhaust gates position in-order to maintain a proper temperature range.

Recapping from the top, exhaust comes out cylinder head exhaust ports to header pipes and continues down individual pipes, through the junction gate and out rear of vehicle. The exhaust gasses chose the least restricted route. Now partially or fully close the gate valve at the end of the header and exhaust gasses will be diverted into the heat exchanger housing pipe and forced past and thru the stainless steel (SS) tubing coil to heat the gasoline before exiting out the exhaust exit pipe. Much heat is absorbed by the gasoline passing thru coils as the gasoline passes from a liquid to a vaporous state in passing thru coil. The gasoline is slightly pressurized and maintained at a consistent low pressure by using one-way, ball check valves that make it impossibly for fuel to leak back out of the heat exchanger.

Stainless Steel (SS) heat exchanger at heart of system,

The (SS) coil is actually a double coil that is wound from (one quarter inch [inside diameter]) tubing. When completed the entire double coil we wound was about 3 inches in diameter and 13 inches in length and if stretched out it would be over 16 feet long.

Rolling this coil requires a lathe that is manually turned with a set of pipe or monkey wrenches. The inner coil is turned around a small pipe as seen in photo. One end of this pipe is locked in lathes chuck. The chuck end of the pipe has a slot grooved into it. This slot will accept a short length of the tubing. About 3-4 inches of the tubing is inserted thru this slot in pipe after pipe is locked in lathe chuck. It is important to keep the ends of the coil tubing straight so they can later have flared fittings installed to allow bolting coil to heat exchanger faceplate as seen in photo. Start manually winding the (SS) tubing around the pipe after it is securely locked in lathe chuck. Do not turn the lathes motor on!. Even at a low speed it will turn too fast to coil tubing safely. You are using the lathe as a way to manually coil the tubing. Have a second person manually turn the lathe by using two pipe wrenches. This person will use two pipe wrenches to grip and turn the far end of coiling pipe, while another person feeds the (SS) tubing around the spinning pipe. It is important to provide spacing around the tube for hot exhaust gasses to pass by tubes so use a sturdy, squared piece of wood (or something that will not scratch the tubing) with dimensions of (3/8-1/2 inch) by (3/8-1/2 inch) and about 8 to 10 inches long. This tool is used to maintain a consistent slot between the tubing for the entire length it is spun onto lathe. The person handling the tubing holds this spacing tool alongside tubing as it is pulled around pipe and uses spacing tool to establish a set distance between last individual winding of coiled tube with coil they are winding. Once the pipes inner coil of tubing is wound to proper length, the entire gizmo, pipe and all is removed from lathe. The next step is to wind the outer coil around the already wound inner coil. For winding the outer coil a piece of pipe that is shorter and has a larger diameter than the original pipe locked in chuck. This larger pipes diameter is just large enough to slip over the first coil of tubing and is only as long as the length of the wound inner coil. The piped coil gizmo with now 2 pipes and one wound (inner) coil is positioned back into the lathe chuck and tightened. The second coil is wound the same way as the first was, but in the opposite direction over the first coil using the spacer tool, and pulled back to the starting end of the inner coil. The gizmo is again removed from the lathe and spacer pipe is slid out from between coils and starting end of quarter inch (SS) tubing is slid out from slotted grove in pipe.

The end of the outer SS coil is carefully bent 90 degrees so to be aimed the same direction as end of inner coil tubing and both ends are then attached to the inside of face plate of heat exchanger housing with SS flare fittings. Be careful to slip the flare fitting over the tubing end prior to flaring the tubing. Also be sure both ends of coil will reach face plate in proper position and one end is not longer than the other. Also it is important when coiling the tubing that one does not end up with a coil that is too long and will not fit within the length of the heat exchanger housing pipe. It is also important to assure that one stops the coiling of outer coil with enough length needed to bend the tubing end 90 degrees to safely and securely plumb it to inside wall of heat exchanger faceplate. It should not be difficult to do the geometry needed to calculate how many inner and outer coils one would expect to get over a given distance. The formula to determine the circumference of a coil is 2(3.14)R. The R is the ratio or half the diameter.

The surge chamber could be a length of pipe positioned in a hot spot directly alongside the header and insulated to maintain heat. It could also be fitted inside the heat exchanger housing with one end of SS coil shorter or longer to accommodate the surge chamber. The surge chamber in photograph (D) is 3-4 times larger than what is needed and when this large it will become harder to keep insulated and hot.

It is highly recommended that all fuel lines in system located downstream from the (SS) coil in heat exchanger be constructed from (SS) tubing and the line that passes from the heat exchanger to the engine intake manifold be constructed from braided/flexible (SS) tubing.

Welded to the faceplate in photo (D) is a channel used to convey the vaporous gasses from the coiled tubing in the heat exchanger over to the external surge tank. A better and simpler design would be to use a short piece of pipe with a gravity fed trap on one end used to trap and later remove all crud and mysterious? solids that fail to vaporize with the gasoline. (Examining these trapped solids leads one to ponder just what compounds are being used as “additives” in our gasoline). This trap pipe would have plumbed to it a flexible (SS) tubing connected to the carburetion system located on engines intake manifold (diagram C).

Understanding how system works,

The operating principal of this system is as follows. There are two methods to introduce the fuel to engine combustion chamber, and referring to diagram B might be helpful at this point. One route is for liquid gasoline when engine is first started and the other method is for the vaporized gasoline once system is warmed up. On more advanced applications both tasks can be done by fuel injection. This system could also work using a conventional fuel injection system or carburetor when fuel is liquid and a propane type mixer bar (diagram C) when operating in vapor mode. There is one modification to the mixing bar that needs to be added. The incoming air being pulled thru the venturi, past throttle plate and past the spray bar below will cool down the metal spray bar and cause the vaporized gasoline to condense back to liquid on the walls of the spray bar. For this reason it is important to position another piece of pipe (cut in half length wise) alongside and cupped around the spray bar but actually not in contact with the spray bar. This outer pipe is positioned slightly upstream of the spray bar and works to block the flow of incoming air from hitting the spray bar. Diagram C has an example the spraybar and heat shield or half-pipe. It is important to note that all fuel lines between the heat exchanger coil in addition to being stainless steel should also be well insulated, along with insulating the heat exchanger housing and surge chamber to lessen possibility of gasoline condensing to liquid. A good insulation and wrapping for this task is again the ceramic type insulation and cloth wrapping with the reflective coating already mentioned.

The fuel is conveyed from vehicles fuel tank thru vehicles stock tubing routed to engine compartment. Once at engine compartment the fuel is diverted by electric actuated valves (#1 diagram B) either of 2 routes. One route remains in the vehicles stock fuel system and on to carburetor or fuel injection(#s 2A & 3A diagram B). This route is used on starting and warm up mode only. The other route uses an electric fuel pump(#2 diagram B) that pushes the fuel thru a propane vacuum fuel lock (VFF) (#5 diagram B) than on into heat exchanger (#7 diagram B) to be vaporized.

In order to operate vapor system the fuel needs to be maintained at a suitable pressure. Also at times when engine stops running for any reason the flow shuts down automatically using the VFF and a vacuum actuated switch (#6) will shut down power to the relay to the electric fuel pump. Lastly the fuel can not back flow from the hot heat exchanger into the vehicles fuel tank nor allow gas vapors to release to atmosphere. These safety features are maintained by plumbing the electric fuel pump (#2) into a tee junction (#3). This tee has a pressure regulating one-way ball check valve (#4) on a tee exit that is set to open at about 5-6 pounds per square inch (PSI) and routes fuel exiting the tee from this check valve back to the fuel tank. This check valve component is designed to ensure a steady and regulated flow of fuel to the vapor system maintained at 5PSI or less.

The remaining exit from the said tee (#3) goes thru 2 one-way check valves (not shown) that are set to open at 3-5(PSI). One valve regulated at 3-5(PSI) would work fine here but duplicate valve(s) are a failsafe designed to stop back-flow of fuel thru tee. The fuel is than routed thru a propane fuel system vapor check valve (#5) commonly called a (VFF). The VFF remains open anytime the intake manifold maintains vacuum. The purpose of the intake manifold pressure actuated VFF valve is to shut off the flow of fuel entering the heat exchanger at times the engine is stalled or not running. The fuel is pumped thru VFF at 3-5(PSI) when engine is operating and has vacuum in its intake manifold. The fuel is pushed into the coiled (SS) heat exchanger (#7) as a liquid at 3-5(PSI) and exits heat exchanger as a vapor at 3-5(PSI) and forced into another tee where it can either go into the reservoir or conveyed to intake manifold and mixed with incoming air (diagram C and #9,#10 in diagram B) to power the engine. This tee also has a removable pipe that acts as a trap (not shown) and allows all solids that would not vaporize to accumulate via gravity. To clean out these mysterious solids the pipe is removed by unscrewing, cleaned and then replaced.

Regulating how system operates

The simple method we used for operating system was as follows. Mounted to our dashboard was a 3 position switch. One position was off and all fuel was naturally plumbed to stock fuel system. We used this position for starting, warm-up and to get us home in case of any vapor carburetion failures. The second position was to a diverter valve to switch the fuel flow from the stock carburetor thru the electric fuel pump than onto the heat exchanger. The third position was the same as the second with the addition of the electric fuel pump switched on as well. The vehicle is started in position one and once warmed up turned to position two till the carburator is starved for fuel than position 3 where the vapor fuel system takes over carburetion function. We also installed into the vehicles dash a cable for operating the exhaust gate as seen in photos. For more heat we would close the gate and the exhaust would be forced through the heat exchanger. Alongside the gate cable are two gauges normally used in small airplanes to monitor cylinder head temperature. We used these gauges first to monitor the vapor temperature as it went into the intake manifold and also to monitor the exhaust temperature as it left the heat exchanger. The conventional non hybrid electric car will be easier to operate in the vapor mode if the road conditions are consistent and it is possible to maintain a steady RPM range. Varying RPMs will make it more difficult to maintain an exhaust gate position heat range that the engine will like.

Use this knowledge at your own risk while exercising an utmost respect for the dangerous nature of gasoline if reading this leads to further studying of this art and possibly building your own vaporized gasoline carburetion system. The authors take no responsibility for any damages or injuries incurred from any person(s) working in this art. Gasoline like propane is highly flammable and explosive, handle with extreme care!

It seems the oil companies and the auto companies cannot figure this out so lets work to enlighten them on how to build a car properly. People are dieing because of wars over dirty crude oil and the earths atmosphere is getting destroyed and causing global climate change while many powerful governmental world leaders are running out of common sense and empathy for the citizens of the world. It looks like it is up to “We the People” once again to fix things and start leading our supposed leaders. The power for making positive change is in all our hands! We just need to start believing it and assert our responsibility to reclaim this power. We also must remain human so we can laugh, cry, shout, cuss, inspire, nurture and share.

Have fun and be safe, FM

==== The Holocene ====

[[File:Holocene Temperature Variations.png|right|thumb|upright=1.35|Temperature change over the past 12 000 years, from various sources. The thick black curve is an average.]]

The [[Holocene]] is characterized by a long-term cooling starting after the [[Holocene climatic optimum|Holocene Optimum]], when temperatures were probably only just below current temperatures (second decade of the 21st century),<ref>{{Cite journal|last1=Kaufman|first1=Darrell|last2=McKay|first2=Nicholas|last3=Routson|first3=Cody|last4=Erb|first4=Michael|last5=Dätwyler|first5=Christoph|last6=Sommer|first6=Philipp S.|last7=Heiri|first7=Oliver|last8=Davis|first8=Basil|date=30 June 2020|title=Holocene global mean surface temperature, a multi-method reconstruction approach|journal=Scientific Data|language=en|volume=7|issue=1|page=201|doi=10.1038/s41597-020-0530-7|pmid=32606396|pmc=7327079|bibcode=2020NatSD...7..201K|issn=2052-4463|doi-access=free}}</ref> and a strong [[African Monsoon]] created grassland conditions in the [[Sahara]] during the [[Neolithic Subpluvial]]. Since that time, several [[stadial|cooling events]] have occurred, including:

*the [[Piora Oscillation]]

*the [[Middle Bronze Age Cold Epoch]]

*the [[Iron Age Cold Epoch]]

*the [[Little Ice Age]]

*the phase of cooling c. 1940–1970, which led to [[global cooling]] hypothesis

In contrast, several warm periods have also taken place, and they include but are not limited to:

*a warm period during the apex of the [[Minoan civilization]]

*the [[Roman Warm Period]]

*the [[Medieval Warm Period]]

*[[Modern Warming|Modern warming]] during the 20th century

Certain effects have occurred during these cycles. For example, during the Medieval Warm Period, the [[American Midwest]] was in drought, including the [[Sand Hills (Nebraska)|Sand Hills of Nebraska]] which were active [[sand dune]]s. The [[black death]] plague of ''[[Yersinia pestis]]'' also occurred during Medieval temperature fluctuations, and may be related to changing climates.

Photo captions (numbers on back)

1. Using lathe to wind first coil around grooved pipe locked in lathe. (pipe wrenches not in photo)

2. Showing how tubing end is positioned into grooved pipe that is locked into lathe chuck.

3. View of positioning of outer pipe around inner coil before pulling second outer coil on lathe.

4. Close up view of double SS coil securely fitted to inside of heat exchanger faceplate with flared fittings.

5. View of SS coil and oversized surge tank with front of heat exchanger on left side.

6. Exhaust header with heat exchanger disassembled from header.

7. Exhaust header with SS coil positioned inside. Note hose clamp positioned around heat exchanger exhaust pipe. Piece of wire under clamp is end of sending wire to the exhaust temperature gauge on dash.

8. Bottom view of exhaust manifold with sample of ceramic insulation alongside.

9. Engine side view of complete exhaust manifold with re-convergence pipe bolted to flange set.

10. Close up view of exhaust gate, note cobwebs from sitting in basement.

11. Rear view of exhaust manifold with re-convergence pipe disconnected.

12. Close up view of two separate exhaust routes before they re-converge.

13. Top view of gate at bottom of photo. Bolt on left is to secure outer wall of gate cable. Pipes on right side of flanges are the re-convergence pipe.

14. View of cable on left side, Vapor temperature gauge in center and exhaust temperature gauge on right.

To find out more or view this info for free on the web visit;

http://byronw.www1host.com/ [e-mail]

Solar activity may have contributed to part of the modern warming that peaked in the 1930s. However, solar cycles fail to account for warming observed since the 1980s to the present day.{{Citation needed|date=September 2016}} Events such as the opening of the [[Northwest Passage]] and recent record low ice minima of the modern [[Arctic shrinkage]] have not taken place for at least several centuries, as early explorers were all unable to make an Arctic crossing, even in summer. Shifts in [[biome]]s and habitat ranges are also unprecedented, occurring at rates that do not coincide with known climate oscillations {{Citation needed|date=September 2016}}.

== References ==

=== Modern climate change and global warming ===

*Emanuel, K. A. (2005) ''Increasing destructiveness of tropical cyclones over the past 30 years.'', ''Nature'', '''436'''; 686-688 {{PDFlink|ftp://texmex.mit.edu/pub/emanuel/PAPERS/NATURE03906.pdf}}

{{main|Climate change}}

As a consequence of humans emitting [[greenhouse gas]]es, [[Surface air temperature|global surface temperatures]] have started rising. Global warming is an aspect of modern climate change, a term that also includes the observed changes in precipitation, storm tracks and cloudiness. As a consequence, glaciers worldwide have been found to be [[The Retreat of Glaciers Since 1850|shrinking significantly]].<ref name="Zemp-2008">{{cite report|url=http://www.grid.unep.ch/glaciers/pdfs/summary.pdf|title=United Nations Environment Programme&nbsp;– Global Glacier Changes: facts and figures|last=Zemp|first=M.|author2=I.Roer|author3=A.Kääb|author4=M.Hoelzle|author5=F.Paul|author6=W. Haeberli|access-date=21 June 2009|archive-url=https://web.archive.org/web/20090325100332/http://www.grid.unep.ch/glaciers/pdfs/summary.pdf|year=2008|archive-date=25 March 2009|url-status=dead}}</ref><ref name="EPA-2016">{{cite web|url=https://www.epa.gov/climate-indicators/climate-change-indicators-glaciers|title=Climate Change Indicators: Glaciers|last=EPA, OA|first=US|website=US EPA|date=July 2016|access-date=26 January 2018|archive-date=29 September 2019|archive-url=https://web.archive.org/web/20190929003522/https://www.epa.gov/climate-indicators/climate-change-indicators-glaciers|url-status=live}}</ref> Land ice sheets in both [[Antarctica]] and [[Greenland]] have been losing mass since 2002 and have seen an acceleration of ice mass loss since 2009.<ref>{{cite web|url=https://climate.nasa.gov/vital-signs/land-ice/|title=Land ice – NASA Global Climate Change|access-date=10 December 2017|archive-date=23 February 2017|archive-url=https://web.archive.org/web/20170223211832/https://climate.nasa.gov/vital-signs/land-ice/|url-status=live}}</ref> Global sea levels have been rising as a consequence of thermal expansion and ice melt. The decline in Arctic sea ice, both in extent and thickness, over the last several decades is further evidence for rapid climate change.<ref>{{cite web|url=https://climate.nasa.gov/evidence/|title=Climate Change: How do we know?|editor1-last=Shaftel|editor1-first=Holly|website=NASA Global Climate Change|publisher=Earth Science Communications Team at NASA's Jet Propulsion Laboratory|access-date=16 December 2017|archive-date=18 December 2019|archive-url=https://web.archive.org/web/20191218104252/https://climate.nasa.gov/evidence/|url-status=live}}</ref>

*IPCC. (2007) ''Climate change 2007: the physical science basis (summary for policy makers)'', IPCC.

==== Variability between regions {{anchor|Contemporaneous regional variability}} ====

*Jones, C. ''Climate Change: Facts and Impacts'' [online]. Available from: [http://www.thewatt.com/modules.php?name=Downloads&d_op=getit&lid=7 What effects are we seeing now and what is still to come?]

{{Gallery

|align=right | height=150 |mode=packed

|title= Examples of regional climate variability

| File:Land vs Ocean Temperature.svg

*Miller, C. and Edwards, P. N. (ed.)(2001) ''Changing the Atmosphere: Expert Knowledge and Environmental Governance'', MIT Press

| '''Land-ocean.''' Surface air temperatures over land masses have been increasing faster than those over the ocean,<ref name="NASA GISS">{{cite web |title=GISS Surface Temperature Analysis (v4) / Annual Mean Temperature Change over Land and over Ocean |url=https://data.giss.nasa.gov/gistemp/graphs_v4/ |website=NASA GISS |archive-url=https://web.archive.org/web/20200416074510/https://data.giss.nasa.gov/gistemp/graphs_v4/ |archive-date=16 April 2020 |url-status=live}}</ref> the ocean absorbing about 90% of excess heat.<ref name="Harvey-2018">{{cite magazine |last1=Harvey |first1=Chelsea |title=The Oceans Are Heating Up Faster Than Expected |url=https://www.scientificamerican.com/article/the-oceans-are-heating-up-faster-than-expected/ |magazine=Scientific American |date=1 November 2018 |archive-url=https://web.archive.org/web/20200303222236/https://www.scientificamerican.com/article/the-oceans-are-heating-up-faster-than-expected/ |archive-date=3 March 2020 |url-status=live }} Data from [https://web.archive.org/web/20200416074510/https://data.giss.nasa.gov/gistemp/graphs_v4/ NASA GISS].</ref>

|File:20200505 Global warming variability - Northern vs Southern hemispheres.svg

*Ruddiman, W. F. (2003) ''The anthropogenic greenhouse era began thousands of years ago'', ''Climate Change'' '''61''' (3): 261-293

| '''Hemispheres.''' The Hemispheres' average temperature changes<ref name="NASA GISS-3">{{cite web |title=GISS Surface Temperature Analysis (v4) / Annual Mean Temperature Change for Hemispheres |url=https://data.giss.nasa.gov/gistemp/graphs_v4/ |website=NASA GISS |archive-url=https://web.archive.org/web/20200416074510/https://data.giss.nasa.gov/gistemp/graphs_v4/ |archive-date=16 April 2020 |url-status=live}}</ref> have diverged because of the North's greater percentage of landmass, and due to global ocean currents.<ref name="Freedman-2013">{{cite web |last1=Freedman |first1=Andrew |title=In Warming, Northern Hemisphere is Outpacing the South |url=https://www.climatecentral.org/news/in-global-warming-northern-hemisphere-is-outpacing-the-south-15850 |website=Climate Central |archive-url=https://web.archive.org/web/20191031123759/https://www.climatecentral.org/news/in-global-warming-northern-hemisphere-is-outpacing-the-south-15850 |archive-date=31 October 2019 |date=9 April 2013 |url-status=live }}</ref>

| File:20200314 Temperature changes for three latitude bands (5MA, 1880- ) GISS.svg

*Ruddiman, W. F. (2005) ''Plows, Plagues and Petroleum: How Humans Took Control of Climate'', Princeton University Press

| '''Latitude bands.''' Three latitude bands that respectively cover 30, 40 and 30 percent of the global surface area show mutually distinct temperature growth patterns in recent decades.<ref name="NASA GISS-2">{{cite web |title=GISS Surface Temperature Analysis (v4) / Temperature Change for Three Latitude Bands |url=https://data.giss.nasa.gov/gistemp/graphs_v4/ |website=NASA GISS |archive-url=https://web.archive.org/web/20200416074510/https://data.giss.nasa.gov/gistemp/graphs_v4/ |archive-date=16 April 2020 |url-status=live}}</ref>

| File:1960- Warming stripes global temperature graphic - atmospheric heights and ocean depths.png

*Ruddiman, W. F., Vavrus, S. J. and Kutzbach, J. E. (2005) ''A test of the overdue-glaciation hypothesis'', ''Quaternary Science Review'', '''24''':11

| '''Altitude.''' A [[warming stripes]] graphic ({{blue|blues}} denote cool, {{red|reds}} denote warm) shows how the greenhouse effect traps heat in the lower atmosphere and oceans, so that the upper atmosphere, receiving less reflected energy, cools.<ref name=AMS_20250501>{{cite journal |last1=Hawkins |first1=Ed |last2=Williams |first2=Richard G. |last3=Young |first3=Paul J. |last4=Berardelli |first4=Jeff |last5=Burgess |first5=Samantha N. |last6=Highwood |first6=Ellie |last7=Randel |first7=William |last8=Roussenov |first8=Vassil |last9=Smith |first9=Doug |last10=Placky |first10=Bernadette Woods |title=Warming Stripes Spark Climate Conversations: From the Ocean to the Stratosphere |journal=Bulletin of the American Meteorological Society |volume=6 |issue=5 |date=1 May 2025 |pages=E964-E970 |doi=10.1175/BAMS-D-24-0212.1|doi-access=free }}</ref><ref name=Hawkins-2019>{{cite web |last1=Hawkins |first1=Ed |title=Atmospheric temperature trends |url=http://www.climate-lab-book.ac.uk/2019/atmospheric-temperature-trends/ |website=Climate Lab Book |archive-url=https://web.archive.org/web/20190912192530/http://www.climate-lab-book.ac.uk/2019/atmospheric-temperature-trends/ |archive-date=12 September 2019 |date=12 September 2019 |url-status=live }} (Higher-altitude cooling differences attributed to ozone depletion and greenhouse gas increases; spikes occurred with volcanic eruptions of 1982–83 (El Chichón) and 1991–92 (Pinatubo).)</ref>

| File:20200505 Global warming variability - global vs Caribbean.svg

| '''Global versus regional.''' For geographical and statistical reasons, larger year-to-year variations are expected<ref name="Meduna-2018">{{cite news |last1=Meduna |first1=Veronika |title=The climate visualisations that leave no room for doubt or denial |url=https://thespinoff.co.nz/science/17-09-2018/the-climate-visualisations-that-leave-no-room-for-doubt-or-denial/ |work=The Spinoff |date=17 September 2018 |archive-url=https://web.archive.org/web/20190517104250/https://thespinoff.co.nz/science/17-09-2018/the-climate-visualisations-that-leave-no-room-for-doubt-or-denial/ |archive-date=17 May 2019 |___location=New Zealand |url-status=live }}</ref> for localized geographic regions (e.g., the Caribbean) than for global averages.<ref name="NCDC_NOAA">{{cite web |title=Climate at a Glance / Global Time Series |url=https://www.ncdc.noaa.gov/cag/global/time-series/globe/land_ocean/12/12/1880-2019 |website=NCDC / NOAA |archive-url=https://web.archive.org/web/20200223062050/https://www.ncdc.noaa.gov/cag/global/time-series/globe/land_ocean/12/12/1880-2019 |archive-date=23 February 2020 |url-status=live}}</ref>

| File:20200509 Emergence of temperatures from range of normal historical variability - tropical vs northern Americas (Hawkins).gif

*Schmidt, G. A., Shindel, D. T. and Harder, S. (2004) ''A note of the relationship between ice core methane concentrations and insolation'' GRL v31 L23206

| '''Relative deviation.''' Though northern America has warmed more than its tropics, the tropics have more clearly departed from normal historical variability (colored bands: 1σ, 2σ standard deviations).<ref name="Hawkins-2020">{{cite web |last1=Hawkins |first1=Ed |title=From the familiar to the unknown |url=https://www.climate-lab-book.ac.uk/2020/from-the-familiar-to-the-unknown/ |website=Climate Lab Book (professional blog) |archive-url=https://web.archive.org/web/20200423232229/https://www.climate-lab-book.ac.uk/2020/from-the-familiar-to-the-unknown/ |archive-date=23 April 2020 |date=10 March 2020 |url-status=live }} ([https://web.archive.org/web/20200502073245/http://www.climate-lab-book.ac.uk/files/2020/03/emerge_example.png Direct link to image]; Hawkins credits [[Berkeley Earth]] for data.) "The emergence of observed temperature changes over both land and ocean is clearest in tropical regions, in contrast to the regions of largest change which are in the northern extra-tropics. As an illustration, northern America has warmed more than tropical America, but the changes in the tropics are more apparent and have more clearly emerged from the range of historical variability. The year-to-year variations in the higher latitudes have made it harder to distinguish the long-term changes."</ref>

}}

[[File:1880- Global warming by latitude zone - NASA - GISS data.webm|thumb| upright=1.15| Global warming has varied substantially by latitude, with the northernmost latitude zones experiencing the largest temperature increases.]]

In addition to global climate variability and global climate change over time, numerous climatic variations occur contemporaneously across different physical regions.

The oceans' absorption of about 90% of excess heat has helped to cause land surface temperatures to grow more rapidly than sea surface temperatures.<ref name="Harvey-2018"/> The Northern Hemisphere, having a larger landmass-to-ocean ratio than the Southern Hemisphere, shows greater average temperature increases.<ref name="Freedman-2013"/> Variations across different latitude bands also reflect this divergence in average temperature increase, with the temperature increase of northern [[wikt:extratropics|extratropics]] exceeding that of the tropics, which in turn exceeds that of the southern extratropics.<ref name="NASA GISS-2"/>

Upper regions of the atmosphere have been cooling contemporaneously with a warming in the lower atmosphere, confirming the action of the greenhouse effect and ozone depletion.<ref name="Hawkins-2019"/>

Observed regional climatic variations confirm predictions concerning ongoing changes, for example, by contrasting (smoother) year-to-year global variations with (more volatile) year-to-year variations in localized regions.<ref name="Meduna-2018"/> Conversely, comparing different regions' warming patterns to their respective historical variabilities, allows the raw magnitudes of temperature changes to be placed in the perspective of what is normal variability for each region.<ref name="Hawkins-2020"/>

Regional variability observations permit study of regionalized [[Tipping points in the climate system|climate tipping point]]s such as rainforest loss, ice sheet and sea ice melt, and permafrost thawing.<ref name="Lenton-2019">{{Cite journal|last1=Lenton|first1=Timothy M.|last2=Rockström|first2=Johan |last3=Gaffney|first3=Owen|last4=Rahmstorf|first4=Stefan|last5=Richardson|first5=Katherine|last6=Steffen |first6=Will|last7=Schellnhuber|first7=Hans Joachim|date=27 November 2019|title=Climate tipping points – too risky to bet against|journal=Nature|language=en|volume=575|issue=7784|pages=592–595|pmid=31776487 |bibcode=2019Natur.575..592L|doi=10.1038/d41586-019-03595-0|doi-access=free|hdl=10871/40141|hdl-access=free}} Correction dated 9 April 2020</ref> Such distinctions underlie research into a possible [[abrupt climate change|global cascade of tipping points]].<ref name="Lenton-2019" />

== See also ==

{{Portal|Environment|Global warming|Energy}}

* [[Climatological normal]]

* [[Anthropocene]]

* [[Ocean heat content]]

{{clear}}

== Notes ==

{{Reflist}}

<div class="references-small"><references/></div>

== External linksReferences ==

* {{cite book |last=Cronin |first=Thomas N. |title=Paleoclimates: understanding climate change past and present |___location=New York |publisher=Columbia University Press |year=2010 |isbn=978-0-231-14494-0 }}

<!-- ATTENTION! Please do not add links without discussion and consensus on the talk page. Undiscussed links will be removed. -->

* {{Cite book |ref= {{harvid|IPCC AR4 WG1|2007}} |title = Climate Change 2007: The Physical Science Basis |series = Contribution of Working Group I to the [[IPCC Fourth Assessment Report|Fourth Assessment Report]] of the Intergovernmental Panel on Climate Change |author = IPCC |author-link = IPCC |year = 2007 |display-editors= 4 |editor-first1= S. |editor-last1= Solomon |editor-first2= D. |editor-last2= Qin |editor-first3= M. |editor-last3= Manning |editor-first4= Z. |editor-last4= Chen |editor-first5= M. |editor-last5= Marquis |editor-first6= K.B. |editor-last6= Averyt |editor-first7= M. |editor-last7= Tignor |editor-first8= H.L. |editor-last8= Miller |publisher = Cambridge University Press |url = https://archive.ipcc.ch/pdf/assessment-report/ar4/wg1/ar4_wg1_full_report.pdf |isbn = 978-0-521-88009-1}} (pb: {{ISBN|978-0-521-70596-7}}).

* [http://www.epa.gov/climatechange/ US EPA climate change and global warming website]

* {{Cite book |ref= {{harvid|IPCC AR4 SYR|2008}} |author= IPCC |author-link= IPCC |year= 2008 |title= Climate Change 2008: Synthesis Report |series= Contribution of Working Groups I, II and III to the [[IPCC Fourth Assessment Report|Fourth Assessment Report]] of the Intergovernmental Panel on Climate Change |editor1= The Core Writing Team |editor-first2= R.K. |editor-last2= Pachauri |editor-first3= A.R. |editor-last3= Reisinger |publisher= IPCC |place= Geneva, Switzerland |isbn= 978-92-9169-122-7 |url= https://www.ipcc.ch/site/assets/uploads/2018/02/ar4_syr_full_report.pdf}}

*[http://digital.library.unt.edu/govdocs/crs/search.tkl?q=climate&search_crit=title&search=Search&date1=Anytime&date2=Anytime&type=form Congressional Research Service (CRS) Reports regarding Climate change]

* {{Cite book|title=Climate Change : A multidisciplinary approach|last=Burroughs|first=William James|publisher=Cambridge university press|year=2001|isbn=0521567718|___location=Cambridge}}

*[http://www.pewclimate.org/ The Pew Center on Global Climate Change]

* {{Cite book|title=Climate Change : A multidisciplinary approach|last=Burroughs|first=William James|publisher=Cambridge University Press|year=2007|isbn=978-0-511-37027-4|___location=Cambridge}}

* {{PDFlink|[http://dels.nas.edu/dels/rpt_briefs/climate-change_final.pdf NAS]}}: [[National Academy of Sciences]]: Understanding and Responding to Climate change, Overview.

* {{Cite book|title=Earth's climate : Past and Future|last=Ruddiman|first=William F.|publisher=W. H. Freeman and Company|year=2008|isbn=978-0716784906|___location=New York}}

* [http://www.ametsoc.org/POLICY/2007climatechange.html Climate Change - An Information Statement of the American Meteorological Society], updated Feb. 2007.

* {{cite book|title=Climatology|last1=Rohli|first1=Robert. V.|last2=Vega|first2=Anthony J.|publisher=Jones & Bartlett Learning|year=2018|isbn=978-1284126563|edition=4th}}

* [http://www.nature.org/initiatives/climatechange/issues/ Summary of the Impacts of Climate Change] from [[The Nature Conservancy]]

* [http://www.panda.org/climate Climate change and global warming] - [[WWF (conservation organization)]].

* [http://www.unep.org/themes/climatechange/ United Nations Environmental Program (UNEP)]: Climate Change Page

* [http://globalchange.org/ Global Change] by the [[Pacific Institute]]

* [http://unfccc.int/essential_background/feeling_the_heat/items/2907.php The UN Climate Change Secretariat]

* [http://www.acia.uaf.edu/pages/overview.html Impacts of a Warming Arctic: Arctic Climate Impact Assessment] (2004) by the [[Arctic Climate Impact Assessment]] – [http://www.greenfacts.org/en/arctic-climate-change/index.htm Summary] by [[GreenFacts]]

* [http://www.tate.org.uk/tateetc/issue9/microtate.htm Special Feature in Spring 2007 issue of '''TATE ETC.''' magazine]

* [http://www.greenfacts.org/en/climate-change-ar4/index.htm Climate Change] - A popularized version of the IPCC Fourth Assessement Report, by [[GreenFacts]]

* [http://www.ecoresearch.net/climate Media Watch on Climate Change] - Visual Interface to Current Articles from 150 News Media Sites

* [http://www.wmo.int/pages/prog/etr/pdf_web/926E.pdf Introduction to climate change: Lecture notes for meteorologists] ([[WMO]]

* [http://e-alkalinesoilsterrapreta.blogspot.com/ Climate Mitigation Action] - Carbon Sequestration Model

===BBCExternal articles=links==

{{Library resources box}}

*Nov 2006: [http://news.bbc.co.uk/1/hi/sci/tech/6189600.stm Carbon emissions show sharp rise]

*{{Commonscatinline|Climate variability and change}}

*Oct 2006: [http://news.bbc.co.uk/2/hi/in_depth/sci_tech/2004/climate_change/ Guide to Climate Change]

*[https://climate.nasa.gov/ Global Climate Change] from [[NASA]] (US)

*Nov 2005: [http://news.bbc.co.uk/1/hi/world/americas/4400534.stm 'Gas muzzlers' challenge Bush]

*[https://ipcc.ch/ Intergovernmental Panel on Climate Change (IPCC)]

*Oct 2005: [http://news.bbc.co.uk/1/hi/sci/tech/4315968.stm Earth - melting in the heat?]

*[https://science.nasa.gov/earth-science/oceanography/ocean-earth-system/climate-variability Climate Variability] {{Webarchive|url=https://web.archive.org/web/20230530121638/https://science.nasa.gov/earth-science/oceanography/ocean-earth-system/climate-variability |date=30 May 2023 }} – NASA Science

*Oct 2005: [http://news.bbc.co.uk/1/hi/sci/tech/4381960.stm Europe study shows climate risks]

*[https://www.ncdc.noaa.gov/climate-information/climate-change-and-variability Climate Change and Variability, National Centers for Environmental Information] {{Webarchive|url=https://web.archive.org/web/20210921083150/https://www.ncdc.noaa.gov/climate-information/climate-change-and-variability |date=21 September 2021 }}

*Feb 2005: [http://news.bbc.co.uk/1/hi/sci/tech/4275729.stm Greenhouse gases 'do warm oceans']

*Ongoing: [http://www.bbc.co.uk/sn/hottopics/climatechange/ BBC Climate Change Experiment]

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