"This year is set to be among the three warmest since records began in 1850 and caps a record-warm decade that is a new indication of man-made climate change, the United Nations said on Thursday.

'The trend is of very significant warming,' Michel Jarraud, head of the World Meteorological Organization, told a news conference on the sidelines of a meeting of almost 200 nations in the Caribbean resort of Cancun trying to curb global warming.

He said 2010 so far was slightly warmer than both 1998 and 2005, the previous top two, but could slip if December is a cool month."

Alister Doyle and Timothy Gardner report for Reuters December 3, 2010. [2]