Climate models overheat Antarctica, new study finds

-----A chilling ozone hole-----

Part of the reason that Antarctica has barely warmed has to do with the ozone hole over the continent. The lack of ozone is chilling the middle and upper atmosphere, altering wind patterns in a way that keeps comparatively warm air from reaching the surface. Unlike the rest of the continent, the Antarctic Peninsula has warmed by several degrees, in part because the winds there are drawing in warmer air from the north. The models generally capture these wind changes, although sometimes incompletely.

The study delivered a mixed verdict on Antarctica's potential impact on sea-level rise. The Intergovernmental Panel on Climate Change, which operates under the auspices of the United Nations, has estimated that sea-level rise could amount to 7 to 23 inches (18-59 centimeters) this century, in part because of melting glaciers worldwide. The Geophysical Research Letters paper suggests that warming in Antarctica over the next century could offset that by about 2 inches if the continent warms by 5.4 degrees F (3 degrees C), as computer models have indicated. The reason is that the warmer air over Antarctica would hold more moisture and generate more snowfall, thereby locking up additional water in the continent's ice sheets.

But the authors caution that model projections of future Antarctic climate may be unreliable.

"The research clearly shows that you can actually slow down sea-level rise when you increase temperatures over Antarctica because snowfall increases, but warmer temperatures also have the potential to speed up sea-level rise due to enhanced melting along the edges of Antarctica," says Monaghan, who did some of his research at Ohio State University before coming to NCAR. "Over the next century, whether the ice sheet grows from increased snowfall or shrinks due to more melt will depend on how much temperatures increase in Antarctica, and potentially on erosion at the ice sheet edge by the warmer ocean and rising sea level."

"The current generation of climate models has improved over previous generations, but still leaves Antarctic surface temperature projections for the 21st century with a high degree of uncertainty," adds co-author and NCAR scientist David Schneider. "On a positive note, this study points out that water vapor appears to be the key cause of the problematic Antarctic temperature trends in the models, which will guide scientists as they work to improve the climate simulations."

The University Corporation for Atmospheric Research manages the National Center for Atmospheric Research under primary sponsorship by the National Science Foundation (NSF). Opinions, findings, conclusions, or recommendations expressed in this document are those of the author(s) and do not necessarily reflect the views of the National Science Foundation, NASA, or other funding agencies.