Climate change: Scientists say this decade likely hottest on record

At Copenhagen climate change talks, a research group says this decade is likely to prove the hottest on record.

Enrique Marcarian/Reuters/File
A mass of ice broken off from the Upsala glacier (back) floats on the waters of Lago Argentino, southwest of Argentina in this March 27, 2007 file photo.

COPENHAGEN, DENMARK -- The first decade of the 21st century is shaping up to be the warmest decade on record globally, while 2009 is likely to crack the Top 10 list of warmest years, perhaps rising as high as No. 5.

That's based on a preliminary look at global climate trends released today by the World Meteorological Organization (WMO) at global climate change talks here in the Danish capital. The WMO's data stretches back to 1850.

The numbers are subject to revision, cautions Michel Jarraud, the WMO's secretary-general. A final analysis of the year and decade is due out next March. Still, he says, the figures released today "are pretty solid."

The preliminary report comes as delegates from more than 190 countries are here negotiating their way toward a global climate change agreement -- an effort that would include developed and developing countries.

The goal is to take actions to reduce emissions of greenhouse gases in a way that puts the world on a path to hold warming to roughly 2 degrees C (3.6 degrees F.) above pre-industrial levels.

The National Oceanic and Atmospheric Administration concurs that this decade was probably the hottest since 1850, noting that average global surface temperatures are expected to reach 0.96 degree F. above the 20th-century average. This will easily surpass the 1990s value of 0.65 degree F.

During the past year, climate-change skeptics have looked at individual annual average temperatures since 1998 and concluded that global warming has given way to global cooling. But climate specialists tend to look at long-term figures in ways that tease the trend out of the ups and downs of individual annual numbers.

As for this year, 2009 was unusually cool in North America and Canada, according to the WMO's analysis, which is based on readings taken from January through October. But the cooling in North America was more than offset by warmer-than-normal temperatures in other parts of the world. Australia posted its third-hottest year on record. Austral fall temperatures in Argentina, Uruguay, Paraguay, and Brazil hit record highs. China posted its third-warmest year in nearly 60 years. And even with its cool temperatures, the US is still likely to mark 2009 as slightly warmer than normal.

Globally, the preliminary numbers show temperatures in 2009 have been 0.44 degrees C (0.8 degrees F.) warmer than the 1961 to 1990 annual average, which is used as a baseline for comparing annual temperatures. That figure is expected to change somewhat once figures for November and December are factored into the final report.

The results highlight one of the challenges in the public debate over global warming: the tendency to cite weather in one location or a year's pattern for one continent as evidence for or against global warming.

"Warming is not going to be uniform," Mr. Jarraud says. "There will still be cold winters" and colder-than-normal summers, he says. "What we're talking about is trends averaged over large areas and over long periods."

The agency drew its data from repositories at the the US's National Climate Data Center in Asheville, N.C., NASA's Goddard Institute for Space Studies in New York, and in Britain. The data from Britain include information from the embattled Climatic Research Unit (CRU) at the University of East Anglia.

The British university is currently investigating allegations raised in stolen e-mails and other files that scientists at the center used questionable approaches to analyzing global temperature information used to build a case for global warming.

Although the numbers included the CRU's data, the WMO is confident that its report paints an accurate climate picture. If you trace the data from each of the three sources on a graph, Jarraud says, you get similar results.

In addition, the report cites the depleted state of Arctic sea ice, which reached its third lowest summertime extent in 2009, following a 2007 melt-back that led to the smallest expanse of summer sea ice since satellites first began keeping track in 1979. This winter's refreeze is still bellow average, according to the National Snow and Ice Data Center in Boulder, Colo. But the ice pack's regrowth is outpacing that of the fall of 2006, ahead of the record melt the following summer.

What to look for at the Copenhagen climate change talks

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