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

==== Atlas.11.1.5 Summary ====

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Observations show a ''very likely'' widespread, strong warming trend starting in the 1950s in the Antarctic Peninsula. Significant warming trends are observed in other West Antarctic regions and at selected stations in East Antarctica ( ''medium confidence'' ). Antarctic precipitation and SMB showed a significant positive trend over the 20th century according to the ice cores, while large interannual variability masks any existing trend over the satellite period since the end of the 1970s ( ''medium confidence'' ).

An assessment of model performance for the present day shows that high-resolution regional climate models with polar-optimized physics are important for estimating SMB and generating climate information, and show improved realizations compared to reanalyses and GCMs when evaluated against observations. At the same time, CMIP6 GCMs showed an improved representation of the Antarctic near-surface temperature compared to CMIP5, though still struggle with the representation of precipitation. There is therefore ''medium confidence'' in the capacity of climate models to simulate Antarctic climate and SMB changes.

Under all assessed emissions scenarios, both West and East Antarctica are ''very'' ''likely'' to have higher annual mean surface air temperatures and more precipitation, which will have a dominant influence on determining future changes in the SMB ( ''high confidence'' ). However, due to the challenges of model evaluation over the region and the possibility of increased meltwater runoff described above, there is only ''medium confidence'' that the future contribution of the Antarctic SMB to sea level this century will be negative under all greenhouse gas emissions scenarios.

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