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Antarctic Warming Is Detected That Plugs Gap in UN’s Knowledge
By Alex Morales
<!-- WARNING: #foreach: $wnstory.ATTS: null at /bb/data/web/templates/webmacro_en/washingtonstory.wm:266.2 --> <!-- WARNING: #foreach: $wnstory.ATTS: null at /bb/data/web/templates/webmacro_en/washingtonstory.wm:280.19 --> Jan. 21 (Bloomberg) -- Antarctica has warmed for the past 50 years, scientists said, plugging a gap in United Nations knowledge about the true extent of global warming.
Antarctic temperatures rose by 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 today in the journal Nature. Crucially, they found warming across the southern continent’s interior, which UN scientists had previously theorized was cooling.
“This has put the last pieces of the jigsaw in place,” Gareth Marshall, a climatologist at the British Antarctic Survey in Cambridge who wasn’t involved in the research, said today in a telephone interview. “If you consider Antarctica as a whole, it shows a significant warming of similar levels to the rest of the Southern Hemisphere.”
Antarctic temperatures are important because the southern continent’s ice sheets hold enough water to raise sea levels by 57 meters (187 feet). The findings mean 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.”
Michael Crichton
While ice shelves rest on the ocean and don’t raise sea levels when they break up, their loss removes a barrier that slows the flow of the land-based ice sheets toward the sea.
Until now, Antarctica has represented the biggest hole in UN knowledge about the recent evolution of the Earth’s temperatures. The world body in 2007 produced its largest assessment ever of climate change, pointing to planet-wide warming while signaling “a cooling over most of interior Antarctica,” a phenomenon emphasized by the bestselling author Michael Crichton, a skeptic of global warming, in his novel “State of Fear” (HarperCollins, 2004.)
“It’s just more evidence that makes it clear that it’s silly to just cavalierly say, ‘oh, Antarctica’s cooling,’” Steig said.
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.
Ice Shelves Collapsing
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.
“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.
Ozone Hole’s Cooling
“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.”
Most ground-based temperature measurements from Antarctica began in 1957 and the data is largely from coastal areas. Satellite measurements for the interior began in 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.
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 which has larger implications because it’s about one-third of the continent -- about the size of Alaska, California, Texas and Kansas.”
To contact the reporter on this story: Alex Morales in London at amorales2@bloomberg.net .
Last Updated: January 21, 2009 13:00 EST
http://www.bloomberg.com/apps/news?pid=washingtonstory&sid=a3tSsxZOcvnI
By Alex Morales
<!-- WARNING: #foreach: $wnstory.ATTS: null at /bb/data/web/templates/webmacro_en/washingtonstory.wm:266.2 --> <!-- WARNING: #foreach: $wnstory.ATTS: null at /bb/data/web/templates/webmacro_en/washingtonstory.wm:280.19 --> Jan. 21 (Bloomberg) -- Antarctica has warmed for the past 50 years, scientists said, plugging a gap in United Nations knowledge about the true extent of global warming.
Antarctic temperatures rose by 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 today in the journal Nature. Crucially, they found warming across the southern continent’s interior, which UN scientists had previously theorized was cooling.
“This has put the last pieces of the jigsaw in place,” Gareth Marshall, a climatologist at the British Antarctic Survey in Cambridge who wasn’t involved in the research, said today in a telephone interview. “If you consider Antarctica as a whole, it shows a significant warming of similar levels to the rest of the Southern Hemisphere.”
Antarctic temperatures are important because the southern continent’s ice sheets hold enough water to raise sea levels by 57 meters (187 feet). The findings mean 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.”
Michael Crichton
While ice shelves rest on the ocean and don’t raise sea levels when they break up, their loss removes a barrier that slows the flow of the land-based ice sheets toward the sea.
Until now, Antarctica has represented the biggest hole in UN knowledge about the recent evolution of the Earth’s temperatures. The world body in 2007 produced its largest assessment ever of climate change, pointing to planet-wide warming while signaling “a cooling over most of interior Antarctica,” a phenomenon emphasized by the bestselling author Michael Crichton, a skeptic of global warming, in his novel “State of Fear” (HarperCollins, 2004.)
“It’s just more evidence that makes it clear that it’s silly to just cavalierly say, ‘oh, Antarctica’s cooling,’” Steig said.
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.
Ice Shelves Collapsing
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.
“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.
Ozone Hole’s Cooling
“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.”
Most ground-based temperature measurements from Antarctica began in 1957 and the data is largely from coastal areas. Satellite measurements for the interior began in 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.
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 which has larger implications because it’s about one-third of the continent -- about the size of Alaska, California, Texas and Kansas.”
To contact the reporter on this story: Alex Morales in London at amorales2@bloomberg.net .
Last Updated: January 21, 2009 13:00 EST
http://www.bloomberg.com/apps/news?pid=washingtonstory&sid=a3tSsxZOcvnI
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