A variety of methods are used to better understand how Antarctic snowfall and near-surface air temperature have been changing in the later decades of the 20th century.
Polar MM5, a mesoscale atmospheric model optimized for use over polar ice sheets, is employed to simulate Antarctic snowfall for the past two decades. Averaged over the continent, the annual snowfall trends from Polar MM5 are not statistically different from zero, suggesting that recent Antarctic snowfall changes do not mitigate currently observed sea level rise. However, Antarctic snowfall does have strong seasonal and regional variability.
Atmospheric model precipitation fields are blended with ice core accumulation records to reconstruct Antarctic snowfall with spatial and temporal continuity over 1955-2004. The resulting dataset is consistent with the results from the shorter, 1985-2001 Polar MM5 assessment, indicating that there has been no significant net change in Antarctic snowfall since the 1950s, and thus Antarctic snowfall is not mitigating observed global sea level rise as expected, despite recent warming of the overlying atmosphere.
A new Antarctic near-surface air temperature dataset spanning 1960-2005 is constructed and compared with other observationally-based Antarctic near-surface air temperature datasets for the past ~45 years. The datasets indicate that no statistically significant near-surface air temperature trends have occurred annually or seasonally over Antarctica since 1960.
The new snowfall and near-surface temperature records are used to assess five 20th century GCM ensembles run in support of the Intergovernmental Panel on Climate Change Fourth Assessment Report. It is found that the GCMs overestimate annual Antarctic near-surface temperature trends on average by a factor of 3 during the 20th century, and by more than 5 times during the latter half of the 20th century. The GCMs are able to accurately simulate the observed sensitivity of Antarctic snowfall to near-surface temperature of about +5-6 %/K, suggesting that if Antarctic near-surface temperature increases by about 2-3.5 K by the end of the 21st century as the GCMs predict, snowfall will increase by about 10-20%, having a negative impact on sea level of about -0.5 to -1.0 mm/y by 2100.