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Scientific winds blow hot and cold in Antarctica



MCMURDO STATION, Antarctica (CNN) -- Scientists have long agreed that certain changes in climate at the Earth's polar regions would provide some of the earliest evidence of possible global warming. What they can't seem to agree upon is what kind of changes are occurring.

In a span of two weeks, four seemingly contradictory reports citing evidence of rising -- and falling -- temperatures in Antarctica have created a virtual train-wreck of information for climate researchers.

A week after the journal Nature published a report indicating that temperatures were falling, the journal Science painted a different picture based on evidence from another part of the frozen continent.

The latest report says lakes near Antarctica's Weddell Sea are not quite as frozen as they used to be.

A team led by Wendy C. Quayle of the British Antarctic Survey measured the decline in ice cover on freshwater lakes on Signy Island. The lakes, frozen solid through the Antarctic winter, have thawed for increasingly longer periods of the Antarctic summer in recent years.

In 1993, nine lakes on Signy Island were thawed for an average of 63 days longer than they were in the summer of 1980 -- reflecting an increase of about 1 degree Fahrenheit in air temperature in the area.

The report in Nature last week was based on increases measured in the thickness of the West Antarctic Ice Sheet. The findings indicated a falling temperature and challenged some previous measures that indicated the ice sheet was declining.

Global warming scenarios predict substantial melting of the ice sheet, contributing substantially to rising sea levels worldwide.

More evidence of falling temperatures was reported last week by researchers with the U.S. National Science Foundation. They found that in snow-free Antarctic valleys near McMurdo Sound, there has been a roughly 1 degree Fahrenheit decrease in air temperature in the past 35 years.

Cautions against long-term conclusions

But possible support for rising temperatures was given in another article this week: The Antarctic Sun, a weekly newspaper published by the National Science Foundation, reported record warm temperatures at both the South Pole and at McMurdo Station, the main U.S. research station.

Cautions against long-term conclusions

According to the Sun, NSF researchers reported an Antarctic heat wave at McMurdo, with temperatures reaching 51 F on December 30, the highest temperature there since the station was established in 1955. The previous high, set a quarter-century ago, was 49 F.

Also, temperatures at the U.S. Amundsen-Scott Station at the South Pole have rarely ever topped 0 F, but in the first week of January they hit 5 F above zero.

Warming? Cooling? Scientists on both sides caution against drawing any long-term conclusions from the apparently contradictory information.

"There is no way at this point in time to know what is causing this unseasonably warm weather," said Jim Frodge, meteorology manager at McMurdo Station, in an interview with the Antarctic Sun.

One of the authors of last week's report on Antarctica's thickening ice also warned against assumptions that his work undermines predictions of global warming. "It would be overreacting to say that global warming is not happening because of this (report)," said Peter Doran of the University of Illinois at Chicago.

Some scientists have suggested that there's no conflict at all: Some parts of Antarctica may be cooling off while others heat up -- all as a function of fluctuations in local wind and weather patterns, which can shift independent of whatever global trend is under way.

And researchers agree on one important point: More of their research is needed.



 
 
 
 


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