A Push from Above; August 2002; Scientific American Magazine; by Sarah Simpson; 2 Page(s)

About 3,250 square kilometers of Antarctica's Larsen B ice shelf shattered and tore away from the continent's western peninsula early this year, sending thousands of icebergs adrift in a dramatic testimony to the 2.5 degrees Celsius warming that the peninsula has experienced since the 1950s. Those wayward chunks of ice also highlighted a perplexing contradiction in the climate down under: much of Antarctica has cooled in recent decades.

Two atmospheric scientists have now resolved these seemingly disparate trends. David W. J. Thompson of Colorado State University and Susan Solomon of the National Oceanic and Atmospheric Administration Aeronomy Laboratory in Boulder, Colo., say that summertime changes in a mass of swirling air above Antarctica can explain 90 percent of the cooling and about half of the warming, which has typically been blamed on the global buildup of heat-trapping greenhouse gases. But this new explanation doesn't mean that people are off the hook. Thompson and Solomon also found indications that the critical atmospheric changes are driven by Antarctica's infamous ozone hole, which grows every spring because of the presence of chlorofluorocarbons (CFCs) and other human-made chemicals in the stratosphere.