COPENHAGEN - The decade of 2000 to 2009 appears to be the warmest one in the modern record, the World Meteorological Organization reported in a new analysis on Tuesday.

The announcement is likely to be viewed as a rejoinder to a renewed challenge from skeptics to the scientific evidence for global warming, as international negotiators here seek to devise a global response to climate change.

December 8, 2009 - Participants watch an animated projection, showing the effects of the climate change, inside the U.S. Center 09 during the second day of the United Nations Climate Change Conference 2009 in Copenhagen, Denmark. Politicians and environmentalists meet for the United Nations Climate Change Conference 2009 that runs until December 18. (Miguel Villagran/Getty Images) The period from 2000 through 2009 has been "warmer than the 1990s, which were warmer than the 1980s, and so on," Michel Jarraud, the secretary general of the international weather agency, said at a news conference here.

The unauthorized release last month of e-mail messages between climate scientists in Britain and the United States has provided new ammunition to global warming skeptics. Some of the messages seemed to suggest that some data be withheld from the public. Mr. Jarraud said the release of the climate analysis was moved up from year's end to coincide with the international conference on climate change.

The data also indicates that 2009 was also the fifth warmest year on record, he said, although he noted that the figures for the year were incomplete.

The international assessment on temperatures from 2000 to 2009 largely meshes with an interim analysis by the National Oceanic and Atmospheric Administration in the United States, which independently estimates global and regional temperature and other weather trends.

Yet it was the gulf between rich and poor nations, not the science of global warming, that dominated talks here on Tuesday as delegates fretted about different pieces of draft language for a new climate treaty circulating in the halls. A 13-page document that was said to have been drafted by Denmark, the conference's host country, included language calling for mechanisms opposed by poor countries for delivering aid to them to help deal with the impact of climate change. The proposal includes more oversight by donor nations than the developing nations want.

Danish officials said in a statement that the document was in no way a draft for a new agreement and that many such papers were circulating as parties informally traded ideas.

Another document was said to be framed by Brazil, South Africa, India and China. It made no mention of specific commitments on their part and rejected outside auditing of projects to reduce emissions financed by those countries on their own.

A negotiator for a large bloc of developing countries meanwhile challenged rich countries to make far deeper cuts in emissions than they have proposed so far. The negotiator, Lumumba Stanislaus Di-Aping of Sudan, said President Obama should be willing to spend far more to limit climate dangers in the world's most vulnerable regions.

"We have to ask him, when he provided trillions of dollars to save Wall Street, are the children of the world not deserving help to save their lives?" he said.

Mr. Di-Aping spoke on behalf of more than 130 developing countries as well as China.

The European Commission meanwhile welcomed a decision by the United States Environmental Protection Agency to pave the way for imposing federal limits on emissions of carbon dioxide. The so-called endangerment finding by the E.P.A. was "an important signal by the Obama administration that they are serious about tackling climate change and are demonstrating leadership," a spokesman for the European Commission said.

Andreas Carlgren, the environment minister of Sweden, the country that currently holds the rotating presidency of the European Union, said in an e-mail message that the E.P.A. ruling "shows that the United States can do more than they have put on the table." So far Mr. Obama has proposed a 17 percent cut in emissions by 2020 from 2005 levels and deeper cuts in later years.

A major reason that hopes have risen in recent weeks is the expectation that Mr. Obama, who plans to attend the final day of the conference on Dec. 18, will commit the United States to making cuts in greenhouse gases. The United States declined to ratify the Kyoto Protocol, a 1997 agreement on curbing greenhouse gases, because of strong opposition in the Senate and from the Bush administration. The refusal to ratify the protocol has left a lingering mistrust of the United States on environmental issues in parts of the world.

The finding by the E.P.A. is expected to allow Mr. Obama to tell delegates in Copenhagen that the United States is moving aggressively to address the problem even while Congress remains stalled on broader legislation to curb global warming.

Tom Zeller Jr. contributed reporting from Copenhagen, and John M. Broder from Washington.