This year is so far tied for the hottest year in a record dating back to 1850 in a new sign of a warming trend, the three major institutes which calculate global warming estimates told Reuters.
UN climate talks resume next week in Cancún, Mexico, where expectations are no longer for a comprehensive deal to slow warming, but smaller progress for example to curb deforestation, in a bid to agree a pact next year or later.
The previous conference in Copenhagen last year fell short of hopes, countries have agreed a non-binding deal to try to limit warming to less than 2C above pre-industrial levels.
Temperatures are now about 0.8C above pre-industrial levels, and 2010 is about 0.5C above the 1961-1990 average, near the record, with two months' data still to collect.
Even with a possible cool end to the year, 2010 is expected to be no lower than third in a record where 1998 and 2005 are warmest. The UN climate scientists says higher temperatures mean more floods, heatwaves and rising sea levels.
The UN's World Meteorological Organisation will publish an estimate on December 2 of where 2010 ranks. As of now, it lists 1998 and 2005 as the warmest years.