The head of the World Meteorological Organization, a United Nations weather agency, said Tuesday that this decade will "very likely" turn out to be the warmest on record going back to 1850.
Michel Jarraud, the WMO's secretary general, added that 2009 will likely be about the fifth-warmest year on record.
The agency said parts of China experienced their warmest year on record, and Australia, so far, is on track to record its third warmest year.
Only the United States and Canada experienced conditions that were cooler than average, the agency said.
The WMO also said the Arctic sea ice's extent during the melt season ranked the third lowest, after the lowest and second-lowest records set in 2007 and 2008, respectively.
The agency released its findings on the second day of the Copenhagen climate conference.
Delegates at the 192-nation conference, which opened Monday, are trying to reach a new agreement on controlling greenhouse gas emissions.