It is possible the position might change when the final figures for November and December have been factored in, although analysis has already shown that November temperatures for the world were running at "near record levels", the WMO said.
Releasing the figures at the UN Climate Conference in Cancun, Mexico, the WMO said the global combined sea surface and land surface air temperature for 2010 (January-October) "is currently estimated at 0.55C (0.99F) above the 1961-1990 annual average of 14C (57.2F)".
It added: "At present, 2010's nominal value is the highest on record, just ahead of 1998 (January-October anomaly 0.53C) and 2005 (0.52C)."
The WMO's official judgement is cautious, saying merely that "the year 2010 is almost certain to rank in the top three warmest years since the beginning of instrumental climate records in 1850."
However, even if this year's final position is not beyond doubt, it is already certain that the past decade is the hottest 10-year period in the instrumental record. "Over the 10 years from 2001 to 2010, global temperatures have averaged 0.46°C above the 1961-90 average, 0.03°C above the 2000-09 mean, and the highest value yet recorded for a 10-year period," the WMO said - The Independent.