La Nina Cools World, Making 2008 10th-Warmest Year

The global average temperature fell in 2008 as Pacific Ocean winds caused by the La Nina weather phenomenon helped cool the planet, according to Bloomberg.

The worldwide average measured 14.31 degrees Celsius (57.76 Fahrenheit) from January to November, the U.K. government forecaster, the Met Office, said today in a report. That was 0.1 degree below 2007 and 0.21 degree lower than in 1998, the hottest year since global measurements began in the 1800s.

The cooling in 2008 may represent a short-term reversal in an overall warming trend that scientists say is changing the world’s rainfall patterns, melting ice caps and intensifying floods and droughts.

“We don’t expect every year to be a record-breaker,” Peter Stott, head of climate monitoring at the Met Office in the southwestern English city of Exeter, said yesterday in a telephone interview. The 2008 measurement “doesn’t show that global warming has slowed,” he said.

This year, still set to be the 10th-warmest on record, was tempered by La Nina, a phenomenon whereby equatorial winds off South America blow westward across the Pacific, making colder water deep in the ocean well up. A cooler surface on the world’s largest ocean lowers the temperatures of surrounding continents.

Goddard Institute

In a separate report, the Goddard Institute for Space Studies said today that the year from Dec. 1, 2007, to Nov. 30 was the coolest since 2000, partly due to La Nina. It was also the ninth-warmest year since 1880, with all nine occurring from 1998 to 2008, said the institute, part of the U.S. National Aeronautics and Space Administration.

“We understand why the temperatures were depressed this year, and that’s because of the La Nina effect in the Pacific,” Stott said. “Because the Pacific is such a big ocean that means that globally the temperature gets depressed by a bit.”

Rising global temperatures since the 1850s are blamed by scientists largely on emissions of greenhouse gases from vehicles, power plants, factories and deforestation.

Delegates from 189 nations met this month for two weeks of debate in Poznan, Poland, midway through two years of negotiations to craft a treaty to fight global warming by limiting manmade greenhouse-gas emissions.

The Met Office figures are compiled from thousands of measurements throughout the year at sea and on every continent, Stott said. The average is unlikely to change dramatically in December, Stott said.

Though 1998 was the hottest year on record, the average temperature for the 2000s is about 0.2 degree higher than the 1990s, Stott said. The past 12 years have been among the 14 warmest on record, according to Met Office figures.

“There’s a whole wealth of evidence right now that shows global warming is largely caused by humans,” Stott said. One cooler year “is not a sign that global warming has slowed.”