Climate commitment: Difference between revisions

Revision as of 11:47, 22 February 2023

Revision as of 17:27, 2 March 2023

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{{short description|Unavoidable future climate change due to inertial effects}}

{{refimprove|date=December 2012}}

[[File:Annual greenhouse gas index (1980-2017).png|thumb|right|upright=1.5|The ongoing buildup of [[IPCC list of greenhouse gases|long-lived greenhouse gases]] in Earth's atmosphere indicates mankind's commitment to both recent and future climate changes<ref>{{Cite web |url=https://www.globalchange.gov/browse/indicators/annual-greenhouse-gas-index |title=Annual Greenhouse Gas Index |publisher=U.S. Global Change Research Program |archive-date=21 April 2021 |archive-url=https://web.archive.org/web/20210421143115/https://www.globalchange.gov/browse/indicators/annual-greenhouse-gas-index |url-status=live }}</ref><ref>{{Cite web |url=https://www.esrl.noaa.gov/gmd/aggi/ |title=The NOAA Annual Greenhouse Gas Index (AGGI) - An Introduction |publisher=[[NOAA]] Global Monitoring Laboratory/Earth System Research Laboratories |access-date=2 March 2023}}</ref>]]

'''Climate commitment''' describes the fact that Earth's [[climate]] reacts with a delay to influencing factors ("[[climate forcing]]s") such as the presence of [[greenhouse gas]]es. Climate commitment studies attempt to assess the amount of future [[global warming]] that is "committed" under the assumption of some constant level of forcingsforcing. The constant level often used for illustrative purposes is that due to [[carbon dioxide|{{CO2}}]] doubling or quadrupling relative to the pre-industrial level; or the present level of forcing.

{{clear}}

== Basic idea ==

If a [[wiktionary:perturbation|perturbation]] — such as an increase in greenhouse gases or [[solar variation|solar activity]] — is applied to theEarth's [[climate system]] the response will not be immediate, principally because of the large [[heat capacity]] (i.e., [[Volumetric heat capacity#Thermal inertia|thermal inertia]]) of the [[ocean]]s.

:''As an analogue, consider the heating of a thin metal plate (by the sun or by a flame): the plate will warm relatively quickly. If a thick metal block is heated instead, it will take much longer for the entire block to reach [[Thermodynamic equilibrium|equilibrium]] with the imposed heating because of its higher heat capacity.''

[[File:Earth's Heat Accumulation.png|thumb|left|upright=1.2|The accumulation of [[ocean heat content|excess heat in the ocean]], at ever greater depths, measures global warming that has already become "irreversible" in the near term<ref name=EarthSysSciData_20200907>{{cite journal |last1=von Schuckmann |first1=K. |last2=Cheng |first2=L. |last3=Palmer |first3=M. D. |last4=Hansen |first4=J. |last5=Tassone |first5=C. |last6=Aich |first6=V. |last7=Adusumilli |first7=S. |last8=Beltrami |first8=H. |last9=Boyer |first9=T. |last10=Cuesta-Valero |first10=F. J. |display-authors=4 |title=Heat stored in the Earth system: where does the energy go? |journal=Earth System Science Data |date=7 September 2020 |doi=10.5194/essd-12-2013-2020 |doi-access=free |volume=12 |issue=3 |page=2013-2041 |bibcode=2020ESSD...12.2013V }}</ref>]]

Land only stores [[heat]] in the top few meters.

Ocean water, by contrast, can move vertically and store heat within the ocean's depth ([[convection]]).

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== Models ==

{{main|global climate model}}

Recent [[model (abstract)|model]]s forecast that even in the unlikely event of greenhouse gases stabilizing at present levels, the earthEarth would warm by an additional 0.5°C by 2100, a similar rise in temperature to that seen during the 20th century. In 2050, as much as 64% of that commitment would be due to ''past'' natural forcings. Over time, their contribution compared to the human influence will diminish. Overall, the warming commitment at 2005 greenhouse gas levels could exceed 1°C.<ref>{{cite journal |last=Wigley |first=T. M. L. |title=The Climate Change Commitment |journal=Science |volume=307 |issue=5716 |pages=1766–9 |date=17 March 2005 |doi=10.1126/science.1103934 |pmid=15774756 |url=ftp://ftp.soest.hawaii.edu/coastal/Climate%20Articles/Wigley_2005%20Sea%20level%20commitment.pdf |bibcode=2005Sci...307.1766W }}</ref> As ocean waters expand in response to this warming, global [[sea level]]s would mount by about 10 centimeters during that time. These models do not take into account [[ice cap]] and [[glacier]] melting; including those [[climate feedback]] effects would give a 1–1.5°C estimated temperature increase.<ref>{{cite journal |url= http://www.nature.com/news/2005/050314/full/050314-13.html |title= Oceans extend effects of climate change |first=Deirdre |last=Lockwood |date= 2005-05-17 |journal=Nature News |doi=10.1038/news050314-13}} </ref>

==History==