Climate commitment: Difference between revisions

Revision as of 20:30, 5 October 2024

Revision as of 04:27, 17 October 2024

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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]]).

This is why the land surface is observed to warm more than the oceans. It also explains the very large difference in [[climate sensitivity|global surface temperature response]] between

* "[[Transient state|transient]]" climate simulations in which the planet's incoming/outgoing energy flows are substantially out-of-balance and only a shallow ocean model might be utilized, and

* "equilibrium" climate prediction [[Execution (computers)|runs]] in which only a shallow ocean is used and it is assumed that the climate has come to equilibrium and

* "[[Equilibrium state|equilibrium]]" climate simulations in which the energy flows approach a new balance and a full ocean model is needed.<ref>{{cite arXiv | eprint = 1307.6821|title=The Earth's Equilibrium Climate Sensitivity and Thermal Inertia|date=25 July 2013| first1 = B. S. H. | last1 = Royce | first2 = S. H. | last2 = Lam |class=physics.ao-ph}}</ref><ref>{{cite journal |last1=Hansen |first1=J. |last2=Russell |first2=G. |last3=Lacis |first3=A. |last4=Fung |first4=I. |last5=Rind |first5=D. |last6=Stone |first6=P. |url=https://pubs.giss.nasa.gov/docs/1985/1985_Hansen_ha09600g.pdf |title=Climate response times: Dependence on climate sensitivity and ocean mixing |journal=Science |volume=229 |pages=857–850 |year=1985 |issue=4716 |doi=10.1126/science.229.4716.857 |pmid=17777925 |bibcode=1985Sci...229..857H|s2cid=22938919 }}</ref>

* "[[Transient state|transient]]" climate prediction runs in which a full ocean is used and the climate is out of balance.

The "commitment" can apply to variables other than temperature: because of the long mixing time for heat into the deep ocean, a given surface warming commits to centuries of [[sea level rise]] from thermal expansion of the ocean. Also once a certain threshold is crossed, it is likely that a slow melting of the Greenland ice sheet will commit us to a sea level rise of 5m over millennia.