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Humanity's impact on climate has been detected on every continent except Antarctica, or so said the United Nations Intergovernmental Panel on Climate Change (IPCC) in February 2007. No longer: scientists, comparing decades of records from 17 Antarctic weather stations with computer simulations of Earth's climate, found that human-induced global warming has been heating up the continent that is home to the South Pole, as well.
"We have detected the human fingerprint in both the Arctic and Antarctic region[s]," says Peter Stott, a climate modeler at the U.K. Met (meteorological) Office's Hadley Center, and co-author of the study published in the journal Nature Geoscience.
The researchers compared 100 years of weather records from the Arctic and 50-plus years of those kept on Antarctica with the results of four computer models. Their findings: natural influences such as changes in the amount of sunlight or volcanic eruptions did not explain the warming trends, but the results matched when increasing levels of greenhouse gas emissions were added to the mix.
In the past few decades, average Arctic temperatures have warmed roughly 3.6 degrees Fahrenheit (2 degrees Celsius); average temperatures in Antarctica have warmed slightly less than 1.8 degrees Fahrenheit (1 degree Celsius).
Lead study author Nathan Gillett, a climatologist at Environment Canada, the government ministry charged with Canadian environmental protection and issues, notes that the collapse of the Larsen B and Wilkins ice shelves on the Antarctic Peninsula, which has warmed more than any other part of the entire world, has already been linked to global warming.
As if the new finding is not disturbing enough, researchers may have underestimated the temperature change because they gave equal weight to readings from the cold continental interior—where another man-made problem, the ozone hole, has contributed to cooling in the spring and summer—and coastal regions, where warming is more pronounced.
"These areas are most susceptible to climate warming in the coming century in Antarctica, because they are the closest to the melt threshold," says climatologist Andrew Monaghan of the National Center for Atmospheric Research in Boulder, Colo., who was not involved in this study but reviewed the research.
After all, it is those areas that are closest to the melting point that can tip precipitously—as did Arctic Ocean sea ice in recent years. "One quarter to one half of the Antarctic coastline has some substantial warming going on as of now," Monaghan adds.
All told, if the eastern and western Antarctic ice shelves were to melt completely, they would raise sea levels by as much as 230 feet (70 meters); the collapse of smaller shelves like Larsen B has sped up the flow of glaciers behind them into the sea, contributing to the creeping up of high tide levels around the world. And that's likely to get worse before it gets better.
"There will be continued residual warming no matter what greenhouse gas reductions we make," Monaghan warns. "We really need to pay closer attention to what is going on with this ice sheet."