By Tim Hirsch
BBC environment correspondent in Buenos Aires
The World Meteorological Organisation (WMO) has announced that 2004 is expected to be the fourth warmest year worldwide since records began.
And the insurance industry says this year will face unprecedented claims for damage from weather-related disasters.
2004 was the most expensive year ever for insurance payouts
Both sets of figures were released as ministers from 180 countries heard a message from the UN Secretary General Kofi Annan urging an end to doubts and delays on action to combat climate change.
The WMO reported that the average temperature of the world's surface for 2004 was expected to be 0.44C higher than the mean for the period 1961-1990, making it the fourth hottest year since 1861, just behind 2003, but still well below the all-time record year of 1998.
And this year has been the most expensive ever for the insurance industry in terms of payouts for damage from natural disasters such as hurricanes and typhoons.
According to preliminary figures compiled by the leading re-insurer Munich Re, insured damage for the first 10 months of 2004 amounted to $35bn, with the United States facing the biggest bill of $26bn.
Overall economic losses, the majority of which were uninsured, are expected to be about $90bn.
Among the disasters singled out in the report are Hurricane Ivan, which devastated the island of Grenada in September, killing 28 people and causing an estimated $1bn in damaged homes, buildings and agricultural losses.
The report says the insurance industry is also worried that new climate-related risks may be emerging, such as Hurricane Catarina, which hit southern Brazil earlier this year.
It developed in the south Atlantic where the sea temperatures are normally too low for tropical cyclones to form.
Thomas Loster, a climate expert with Munich Re said: "As in 2002 and 2003, the overall balance of natural catastrophes is again clearly dominated by weather-related disasters, many of them exceptional and extreme.
"We need to stop this dangerous experiment humankind is conducting on the Earth's atmosphere."
The figures were released as ministers gathered for the final stage of the UN conference to discuss future action on climate change.
'Seize this moment'
The executive director of the UN environment programme Klaus Toepfer read a message from Mr Annan saying the eyes of the world were on the governments gathered in Buenos Aires.
Mr Annan said: "People around the world want to know that you are working together, on a multilateral basis, to address this challenge with all your creativity and will.
"They want genuine signs that the days of delay and doubt are behind us. I call on you to seize this moment."
Insurance claims are expected to top $20bn
While it did not mention the US by name, the apparent reference was to the refusal of President George W Bush to take on targets to cut greenhouse gas emissions set by the Kyoto protocol, which comes into force next year.
A more obvious attack on the US position came from the President of Argentina, Nestor Kirchner.
He accused rich countries of double standards by insisting on the repayment of financial debt from the developing world, while refusing to acknowledge their own "environmental debt" - since it was the industrialised economies which created the build-up of greenhouse emissions, but the poor who will suffer the worst impacts of global warming.