At the U.N.'s Cancun climate change conference, the World Meteorological Organization reports that 2010 is one of the top three warmest years and that the first decade is the warmest since 1850.  The WMO press release notes:

The year 2010 is almost certain to rank in the top 3 warmest years since the beginning of instrumental climate records in 1850, according to data sources compiled by the World Meteorological Organization (WMO). The global combined sea surface and land surface air temperature for 2010 (January–October) is currently estimated at 0.55°C ± 0.11°C1 (0.99°F ± 0.20°F) above the 1961–1990 annual average of 14.00°C/57.2°F. At present, 2010’s nominal value is the highest on record, just ahead of 1998 (January-October anomaly +0.53°C) and 2005 (0.52°C)2. The ERA-Interim3 reanalysis data are also indicating that January-October 2010 temperatures are near record levels. The final ranking of 2010 will not become clear until November and December data are analysed in early 2011. Preliminary operational data from 1-25 November indicate that global temperatures from November 2010 are similar to those observed in November 2005, indicating that global temperatures for 2010 are continuing to track near record levels.

Over the ten years from 2001 to 2010, global temperatures have averaged 0.46°C above the 1961-1990 average, 0.03°C above the 2000-09 average and the highest value ever recorded for a 10-year period. Recent warming has been especially strong in Africa, parts of Asia, and parts of the Arctic; the Saharan/Arabian, East African, Central Asian and Greenland/Arctic Canada sub-regions have all had 2001-10 temperatures 1.2 to 1.4°C above the long-term average, and 0.7°C to 0.9°C warmer than any previous decade.

To give readers some idea of how 2010 compares with two other warm years (1998 and 2005) I include a graph from National Oceanic and Atmospheric Administration below:

It should be noted that 1998, and 2005, and 2010 were all years in which El Ninos occurred. El Ninos are periodic warmings of the tropical Eastern Pacific Ocean that tend to boost average global temperatures among other effects.

Note: I will be reporting from the Cancun conference next week.