Antartica: In the winter sky over Antarctica, scientists have detected a vast cap of steadily warming air, in the first sign that record levels of greenhouse gases in the atmosphere may be trapping heat above the ice sheets of the South Pole.
The temperature of the winter air over Antarctica has been rising at a rate three times faster than the world as a whole, the researchers reported in the journal Science.
By analysing 30 years of high-altitude weather balloon records, meteorologists at the British Antarctic Survey in Cambridge concluded that temperatures in the polar troposphere - the dense layer of air reaching from the surface to an altitude of about eight kilometres (five miles) - have risen by 3.6 degrees Fahrenheit since the early 1970s.
"We have the largest regional warming on Earth at the tropospheric level," said climate specialist John Turner, who led the research team.
As levels of carbon dioxide in the atmosphere worldwide rise to levels not seen for a million years, the ice sheets of Antarctica - the world's largest reservoir of fresh water - are shrinking faster than new snow can fall.
But no one knows whether the heat-trapping effects of human atmospheric pollution are at fault or nature's own cycles of change.
The dramatic warming made public last Thursday was nowhere evident in any of the climate models on which global warming forecasts are based, Mr Turner said.
The researchers checked their finding against 20 computer simulations used by the United Nations' Intergovernmental Panel on Climate Change to replicate past climate patterns and make predictions about the future. "We have the classic global warming signal," Mr Turner said. "It is like the blanket on the bed: When we wrap the Earth with a blanket of greenhouse gases like carbon dioxide and methane, we trap heat under it at the expense of the atmosphere above, which then cools."
The new finding about Antarctic warming is particularly important, several experts said, because until now researchers had only partial - and often conflicting - temperature readings from a few surface stations on the icy continent.
Even as one weather station has reported the fastest warming of anywhere on Earth, others simultaneously reported seasonal cooling.
- (LA Times-Washington Post service)