Antarctic Warming Found by Scientists Dashes Argument

By Alex Morales

Jan. 22 (Bloomberg) -- Antarctica has warmed over the past half-century, scientists said, dashing a key argument by skeptics who say climate change is overstated.

Temperatures rose an average 0.12 degrees Celsius (0.22 Fahrenheit) per decade since 1957, researchers led by Eric Steig, a professor of glaciology at the University of Washington in Seattle, said in the journal Nature. Using new measurement methods, they discovered warming in the continent’s interior, which United Nations-sponsored scientists theorized was cooling.

The findings may help puncture arguments by global-warming skeptics such as the late author Michael Crichton who have pointed to cooling in parts of Antarctica as an indicator that climate change is exaggerated.

“This has put the last pieces of the jigsaw in place,” Gareth Marshall, a British Antarctic Survey climatologist in Cambridge who wasn’t involved in the research, said yesterday in a telephone interview. “If you consider Antarctica as a whole, it shows a significant warming.”

Temperatures in the frigid continent, bigger than the U.S. and Mexico combined, are important because its ice sheets contain enough water to raise sea levels by 57 meters (187 feet). The desolate mass of ice holds the record-low temperature, measured at minus 89 Celsius by the U.S. National Climatic Data Center.

Antarctica had represented the biggest gap in United Nations knowledge about the recent evolution of the Earth’s temperatures and extent of global warming, a phenomenon that has been widely detected in the Arctic at the earth’s other extreme.

Ice Shelves Breaking

The study indicates that the breakup of ice shelves already seen in the Antarctic Peninsula, a spit of land reaching toward South America, may “eventually” extend to other parts of the continent, Steig said in a telephone interview.

“The fact that the warming that is appearing on the peninsula extends way down into West Antarctica would suggest that eventually, if that trend continues, ice shelves in West Antarctica are also going to similarly be affected,” Steig said, pointing to a timeframe of “hundreds of years.”

Ice shelves are attached to land and rest on the oceans, so they don’t raise sea levels when they break up. Even so, their loss removes a barrier to the flow of melting land-based ice sheets toward the sea.

Most ground-based temperature measurements from Antarctica began in 1957, and the data is largely from coastal areas. Gauging the vast interior by satellite didn’t begin until 1979. Steig’s team used mathematical models to establish the relationship between the ground and satellite measurements between 1979 and 2006 and then used the correlation they found to calculate temperatures for the interior going back to 1957.

Cooling Controversy

The UN in 2007 produced its largest assessment of climate change, pointing to planet-wide warming while signaling “a cooling over most of interior Antarctica,” a phenomenon emphasized by Crichton, who died in November, in his novel “State of Fear” (HarperCollins, 2004.)

The book, one of many in the last decade that stirred popular debate over climate change, prompted rebuttals by scientists.

“Readers may understandably take away some misconceptions from his book,” the Cambridge, Massachusetts-based Union of Concerned Scientists wrote on its Web site about Crichton’s novel. Cooling trends in some parts of the world, are “fully compatible with the physics on which climate models are based.”

“Global warming is not causing any significant retreat of polar ice caps,” James M. Taylor, senior fellow for environmental policy at the Heartland Institute, wrote in a report. The Chicago- based research group is planning an international conference March 8-10 in New York City for scientists and analysts who “question the theory” of man-made climate change.

500 Billion Tons

The UN’s 2007 report included temperature-change maps that showed the bulk of Antarctica colored gray, an indication of insufficient data. “Significant warming” was taking place in the Antarctic Peninsula, it said.

The effects of warming in the Antarctic Peninsula have been dramatic. In 2002, the Larsen B ice shelf collapsed, with 500 billion tons of ice breaking up into icebergs in less than a month. The larger Wilkins ice sheet, which is further south, lost 1,000 square kilometers (386 square miles) in 1998 and began to break up further last February.

Over the past 50 years the Antarctic Peninsula warmed an average of 0.11 degrees Celsius a decade, West Antarctica gained 0.17 degrees every 10 years and temperatures in East Antarctica rose by 0.1 degrees, Steig’s team found. The data from the east had a margin of error of 0.07 degrees, meaning the actual warming may be close to zero.

Even so, East Antarctica has cooled by about 0.2 degrees Celsius a decade since the 1970s, the researcher said.

‘It’s Warming’

“The warming prior to that was even greater than the cooling since and therefore, on average, it’s warming,” Steig said. The recent cooling has been attributed to the hole in the ozone layer caused by pollutants that are now banned so the cooling is likely to reverse in coming years, he said.

“Normally when ozone is warmed up by the sun, it causes the stratosphere, which is part of the atmosphere, to warm,” the British Antarctic Survey’s Marshall said. “If the ozone is missing, then that part of the atmosphere will cool and therefore you get this colder air over Antarctica and this propagates downwards toward the surface.”

Because of the statistical uncertainty that still surrounds the data from East Antarctica, Steig said his team’s biggest advance was in establishing there’s a clear warming trend in West Antarctica.

“The magnitude of the trend is larger in West Antarctica so we’re more confident that it’s warming,” Steig said. “We’ve really filled in a huge gap.”

To contact the reporter on this story: Alex Morales in London at amorales2@bloomberg.net.