GENEVA — The warmest year on record is a three-way tie: 2010, 2005 and 1998.
So says the U.N. weather agency, providing further evidence Thursday that the planet is slowly but surely heating up.
Average temperatures globally last year were 0.95 degrees Fahrenheit (0.53 Celsius) higher than the 1961-90 mean that is used for comparison purposes, according to World Meteorological Organization.
That's a bit lower than what the U.S. National Climatic Data Center announced earlier this month, but the World Meterological Organization also uses figures based on data collected by Britain's Meteorological Office and NASA.
"The 2010 data confirm the Earth's significant long-term warming trend," said Michel Jarraud, WMO's top official. He added that the ten warmest years after records began in 1854 have all occurred since 1998.
The average worldwide temperature for the 20th century was 57.0 degrees Fahrenheit.
But rising global temperatures over the last century are causing climate experts to worry. Most atmospheric scientists attribute the change to carbon dioxide and gases released into the air by gasoline-burning engines and other industrial processes. The gases tend to trap heat in the atmosphere like a greenhouse.
The Geneva-based global weather agency noted that last year's extreme weather – notably the heat wave in Russia and monsoon flooding in Pakistan – has continued into the new year. It also cited the heavy floods in Sri Lanka, the Philippines, Brazil and Australia as examples.
The year 2010 also was the wettest on record, according to the Global Historical Climatology Network. But since rain and snowfall patterns varied greatly around the world, scientists say more research is needed to establish a link between the warmer temperatures with the unusual moisture.
Land stations, ships, buoys at sea and satellites are all use to collect temperature readings. A "La Nina" condition took effect in the tropical Pacific Ocean in the last half of 2010, marked by below-normal temperatures.
Other findings in the WMO's climate report included:
_ Arctic sea ice cover in December was the smallest since records began in 1979, with an average monthly extent of 12 million square kilometers (4.6 million square miles). The ice cover is considered a marker of climate change as global warming tends to be seen first at the poles.
_ Recent warming has been especially strong in Africa, parts of Asia, and parts of the Arctic in Greenland and Canada, the agency said. Significantly cooler weather was registered mainly toward the end of the year, especially in northern Europe, parts of Russia and in the eastern United States.