New international climate data show that 2005 is on track to be the hottest year on record, continuing a 25-year trend of rising global...

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WASHINGTON — New international climate data show that 2005 is on track to be the hottest year on record, continuing a 25-year trend of rising global temperatures.

Climatologists at NASA’s Goddard Institute for Space Studies calculated the record-breaking global average temperature — which surpasses 1998’s record by a tenth of a degree Fahrenheit — from readings taken at 7,200 weather stations throughout the world.

The new analysis comes as government and independent scientists are reporting other signs of global warming, such as the record shrinkage of Arctic sea ice and unprecedented high ocean temperatures in the Gulf of Mexico.

Late last month, scientists from the University of Colorado and NASA said the Arctic sea icecap shrank this summer to 200 million square miles, 500,000 square miles less than its average area between 1979 and 2000. In addition, a scientist at the National Oceanic and Atmospheric Administration determined that sea surface temperatures in the Gulf of Mexico were higher in August than at any time since 1890, which may have contributed to the intense hurricanes that struck the region this year.

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“At this point, people shouldn’t be surprised this is happening,” said Goddard atmospheric scientist David Rind, noting that 2002, 2003 and 2004 were among the warmest years on record.

Many climatologists, along with policy-makers in a number of countries, think the rapid temperature rise in the past 50 years is heavily driven by the burning of fossil fuels and other human activities that have spewed carbon dioxide and other “greenhouse gases” into the atmosphere. A vocal minority of scientists, however, says the warming climate is the result of a natural cycle.

Global temperatures this year are about 1.36 degrees Fahrenheit (0.75 Celsius) above the average between 1950 and 1980, according to the Goddard analysis. Worldwide temperatures in 1998 were 1.28 degrees Fahrenheit (0.71 Celsius) above that 30-year average. The data show that Earth is warming more in the Northern Hemisphere, where the average 2005 temperature was two-tenths of a degree above the 1998 level.

Climate experts say such seemingly small shifts are significant because they involve average readings based on measurements taken at thousands of sites. To put it in perspective, the planet’s temperature rose by just 1 to 1.5 degrees Fahrenheit in the past century.

Rind said scientists expect worldwide temperatures to rise another 1 degree Fahrenheit between 2000 and 2030, and an additional 2 to 4 degrees by 2100.

From that perspective, this year’s higher temperatures are “really small potatoes compared to what’s to come,” he said.

But one skeptic, state climatologist George Taylor of Oregon, said it is difficult to determine an accurate global average temperature, especially since there are not enough stations recording ocean temperatures.

“I just don’t trust it,” Taylor said of the new calculation, noting that Goddard’s findings are “mighty preliminary.”

Several scientists said yesterday that Earth’s rapid warming could become self-perpetuating as the buildup of heat in the air, on land and in the sea accelerates. Ted Scambos, the lead scientist at the National Snow and Ice Data Center in Boulder, Colo., said the shrinkage of sea ice in the Arctic makes it more likely that the region will warm faster, because open water absorbs much more heat from the sun than snow and ice.

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