Editing IPCC:AR6/WGI/Chapter-7 (section)

===== 7.4.4.1.3 Overall assessment of polar amplification =====

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Based on mature process understanding of the roles of poleward latent heat transport and radiative feedbacks in polar warming, a high degree of agreement across a hierarchy of climate models, observational evidence, paleoclimate proxy records of past climates associated with CO <sub>2</sub> change, and ESM simulations of those past climates, there is ''high confidence'' that polar amplification is a robust feature of the long-term response to greenhouse gas forcing in both hemispheres. Stronger warming in the Arctic than the global average has already been observed ( [[IPCC:Wg1:Chapter:Chapter-2#2.3.1|Section 2.3.1]] ) and its causes are well understood. It is ''very likely'' that the warming in the Arctic will be more pronounced than the global average over the 21st century ( ''high confidence'' ) [[IPCC:Wg1:Chapter:Chapter-4#4.5.1.1|Section 4.5.1.1]] ). This is supported by models’ improved ability to simulate polar amplification during past time periods, compared with at the time of AR5 ( ''high confidence'' ); although this is based on an assessment of mostly non-CMIP6 models.

Southern Ocean SSTs have been slow to warm over the instrumental period, with cooling since about 1980 owing to a combination of upper-ocean freshening from ice-shelf melt, intensification of surface westerly winds from ozone depletion, and variability in ocean convection ( [[IPCC:Wg1:Chapter:Chapter-9#9.2.1|Section 9.2.1]] ). This stands in contrast to the equilibrium warming pattern either inferred from the proxy record or simulated by ESMs under CO <sub>2</sub> forcing. There is ''high confidence'' that the SH high latitudes will warm more than the tropics on centennial time scales as the climate equilibrates with radiative forcing and Southern Ocean heat uptake is reduced. However, there is only ''low confidence'' that this feature will emerge this century.

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