2011 set to be the 10th-hottest year since records began in 1850, a United Nations weather agency reported Tuesday?in its annual assessment of average global temperatures.

The impact of climate change on icebergs and glaciers. [un.org]?

The World Meteorological Organization's preliminary report, based on the first 10 months of the year, was released in Geneva and at the U.N. climate talks in South Africa. It provided a bleak backdrop to negotiators who are seeking ways to limit pollution blamed for global warming.

"Despite La Ni?a, it was a very, very warm year to the point that it is the warmest decade on record," said WMO Secretary-General Michel Jarraud during a press briefing in Geneva.

La Ni?a is a meteorological phenomenon which is supposed to have a cooling influence on Earth's atmosphere, but Jarraud said Arctic sea ice has also shrunk to record-low volumes this year.

"2011 was a year marked by weather extremes that punished the poorest people in the world and helped send millions into hunger and poverty," said Kelly Dent, policy advisor for Oxfam, a UK-based non-governmental organization.

"From flooding in south-east Asia, which killed more than 1,100 people and helped send the price of rice in Vietnam up 30 percent, to record heat and droughts in the U.S. that crippled agricultural production, extreme weather and rising temperatures was a menace to vulnerable people around the world. This provides a stark reminder of what is at stake in the Durban negotiations," he said.

According to the report, the 13 warmest years have all occurred after 1997, and the period between 2002 and 2011 is the warmest-ever decade, registering 0.46 degrees Celsius above the long-term average.

The report also warns of high levels of concentrations of greenhouse gases in the atmosphere, which are bringing average global temperatures closer to surpassing the recommended two degree Celsius target, which could trigger irreparable changes on the planet.