Drought in Mauritius Africa copyright Clive Shirely/Signum

NASA researchers have calculated that 2005 was the hottest year on record.

Last year produced the highest annual average surface temperature worldwide since instrument recordings began in the late 1800s, according to NASA's Goddard Institute for Space Studies. The previous hottest year was 1998.

The Goddard Institute estimated temperatures in the Arctic from nearby weather stations because no direct data were available. Because of that, the Institute's Director James Hanson told AP, "We couldn't say with 100 percent certainty that it's the warmest year, but I'm reasonably confident that it was."

2005 reached the warmth of 1998 without help of the "El Nino of the century" that pushed temperatures up in 1998.

NASA says the planet is the warmest it's been in 10,000 years. Hansen blames a build-up of heat-trapping greenhouse gases such as carbon-dioxide.

Greenpeace spokesman Jim Footner said: "Global temperatures are reaching crisis point, and still nothing is being done. With 150,000 people dying every year from climate change and the future looking bleaker, leaders like Tony Blair continue to do nothing, blundering along hoping the nuclear industry can bail us out. If we're to stand a chance of stopping climate change, we need to stop wasting time and start leading from the front by reducing energy demand and building renewable energy projects on a huge scale."