Antarctic snowfall may offset sea-level rise.

• Position: Precipitation

When Antarctica's air temperature rises, moisture in the atmosphere increases. That should mean more snowfall on the frozen continent. So, why hasn't that trend become evident in Antarctica's surface mass balance as climate models predict? In a study by scientists at Columbia University, New York, researchers used historical records and climate simulations to examine that question. They found that the effect of rising temperatures on snowfall so far has been overshadowed by Antarctica's large natural climate variability, which comes from random, chaotic variations in the weather.

By mid century, however, as temperatures continue to rise, the study shows how the effect of human-induced warming on Antarctica's net snow accumulation should emerge above the noise.

The expectation of more snowfall is something of a silver lining as temperatures rise. Global warming already is increasing sea level through melting ice and thermal expansion. The increase in snowfall over Antarctica could help reduce the amount of global sea-level rise by about two to three inches by the year 2100, according to the study. That would provide a small, but important, benefit: the Intergovernmental Panel on Climate Change estimates global sea-level...