Arctic is warming up faster than ever, NASA satellite data show

Scientists note reduction in sea ice, say loss will speed temperature rise

October 24, 2003|By Frank D. Roylance | Frank D. Roylance,SUN STAFF

WASHINGTON - The Arctic is warming at an accelerating pace, scientists say, and the consequences won't be limited to the top of the world.

A new report on NASA satellite observations over the past 20 years says average summertime temperatures in the Arctic have climbed about 2.2 degrees Fahrenheit each decade since 1981.

By comparison, it has taken global temperatures a century to increase about 1 degree.

And the pace is quickening.

The Arctic warming has been eight times faster in the past two decades than it was over the past century, according to the study by Josefino Comiso, a research scientist at the NASA Goddard Space Flight Center in Greenbelt. His paper on Arctic warming will appear next week in the American Meteorological Society's Journal of Climate.

The warming trend has been strongest in northern Alaska and Siberia - the same areas where previous studies have reported sharp reductions in the extent of year-round sea ice.

The area of sea ice that survives the Arctic summer has dwindled by 9 percent per decade, reaching a record low last year, according to a NASA-funded study last year by Mark C. Serreze, a research scientist at the University of Colorado.

Serreze said scientists might continue to debate how much of the warming is the result of human activity and how much is natural climate change. But "the fact is that the climate is changing, and the Arctic is changing rapidly."

"We should recognize that change is occurring, and we will need to adapt to it," he said.

Once Arctic warming begins, he said, complex interactions of ocean, sea ice and the atmosphere tend to make it self-sustaining. As the perennial ice retreats, it reflects less solar energy back into space. More energy is absorbed by the sea water, warming it. And as the ocean warms up, the year-round ice retreats even farther.

The new temperature data were gathered by NASA's infrared satellites, giving scientists their first comprehensive and reliable view of Arctic warming trends. Comiso said previous studies were limited by the scarcity of Arctic weather stations and the lack of long-term continuity in their records.

Some Arctic populations are already grappling with warming trend. Native people, seals and polar bears living along the Arctic Ocean have always used the perennial sea ice as a platform for hunting marine animals. As that platform retreats from the shore, they face a loss of access to their food supplies.

The broader expanses of open water exposed to Arctic winds in summer are also creating stronger surf. "That effect, coupled with other effects such as melting permafrost, are creating a really serious coastal erosion problem," said Michael Steele, an oceanographer at the University of Washington in Seattle. Some coastal communities have been forced to move inland.

Towns and cities built on permafrost are seeing damage to buildings and utilities as the soil thaws.

"Changes in the Arctic actually have big implications elsewhere, including here in the continental United States," said David H. Rind, of the NASA Goddard Institute for Space Studies in New York.

On the plus side, he said, retreating sea ice might open shipping lanes across the region, reducing shipping costs between Asia and markets in Europe and eastern North America.

But a total loss of Arctic sea ice could alter U.S. temperature and rainfall. For example, Rind said, computer models suggest Kansas could see a 4-degree increase in winter temperatures and a 40 percent reduction in snow cover. Some might welcome that, but it would reduce winter wheat crops and dry the soil.

Melting Arctic permafrost will release trapped carbon dioxode and methane - both gases that contribute to global warming.

Arctic warming could also shift ocean circulation patterns, displace fisheries and melt glaciers in coastal Greenland, accelerating the rise in global sea levels, scientists say.

The most important message from the new findings on Arctic temperature increases, said Rind, is that global warming "is happening now."

"We can't afford to wait for long periods of time for technical solutions," he said. "Change is in the air, literally."

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