Last year was the sixth-hottest since 1850, with temperatures indicating long-term warming of the planet, the World Meteorological Agency said.

Thirteen of the 14 hottest years since the instrumental record began have occurred this century, including 2010 and 2005, the two warmest, the WMO, a United Nations agency, said in an e-mailed statement. The other year in the ranking, 1998, was the third warmest.

Every decade since 1970 has been warmer than the previous one, and the UN predicts warming will continue as humans spew more greenhouse gases into the atmosphere.

The UN in September said the world has already released more than half the emissions allowable if we're to stop temperatures rising 2 degrees celsius above pre-industrial levels.

“The underlying trend is undeniable,” WMO Secretary- General Michel Jarraud said in the statement. “Given the record amounts of greenhouse gases in our atmosphere, global temperatures will continue to rise for generations to come.”

The average global land and sea temperature in 2013 was about 0.5 degree above the 1961-through-1990 average of 14 degrees, according to the WMO. It was 0.03 degree above the 2001-2010 average.

The WMO bases its calculations largely on three independent datasets, produced by the U.S. National Aeronautics and Space Administration, the National Oceanic and Atmospheric Administration, and a collaboration between the U.K. Met Office and the University of East Anglia. That university said yesterday in a statement that it was making its land-surface air temperature data available via Google Earth.

“The beauty of using Google Earth is that you can instantly see where the weather stations are, zoom in on specific countries, and see station datasets much more clearly,” Tim Osborn, a scientist at the UEA's Climatic Research Unit, said in an e-mailed statement. “We wanted to make this key temperature dataset as interactive and user- friendly as possible.”

Bloomberg