COPENHAGEN — Despite recent fluctuations in global temperature year to year, which fueled claims of global cooling, a sustained global warming trend shows no signs of ending, according to new analysis by the World Meteorological Organization made public on Tuesday.
The decade of the 2000s is very likely the warmest decade in the modern record, dating back 150 years, according to a provisional summary of climate conditions near the end of 2009, the organization said.
The period from 2000 through 2009 has been “warmer than the 1990s, which were warmer than the 1980s and so on,” said Michel Jarraud, the secretary general of the international weather agency, speaking at a news conference at the climate talks in Copenhagen.
The international assessment largely meshes with an interim analysis by the National Climatic Data Center and NASA in the United States, both of which independently estimate global and regional temperature and other weather trends.
Mr. Jarraud also said that 2009, with some uncertainty because several weeks remain, appears to be the fifth warmest year on record.
Addressing questions about the reliability of climate data after the unauthorized release of e-mail messages and files from a British climate research unit that provides data to the global weather group, he said there was no evidence that the various independent estimates showing a warming world were in doubt.
The news conference early Tuesday came after the European Commission reacted to a decision by the United States Environmental Protection Agency to pave the way for federal limits on emissions of carbon dioxide, saying it should give further weight to negotiations under way here aimed at crafting a new global agreement to curb greenhouse gases.
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 from the European Commission said. The finding “gives new momentum following their announcement of cuts,” he said.
Political leaders in Copenhagen welcomed the ruling, but they were quick to press the Obama administration to do more now to sweeten its offer.
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 on Tuesday morning that the ruling “shows that the United States can do more than they have put on the table.”
Connie Hedegaard, the Danish politician who was elected on Monday as president of the conference, said in an e-mail message on Tuesday morning that the ruling in the United States “is a helpful step, as it could provide a larger degree of flexibility in the negotiations.” So far President Obama has signaled a cut emissions by about 17 percent by 2020 compared with 2005 levels. The White House also has indicated that the United States would contribute to a fund to tackle climate change.
The gathering of more than 190 nations in Copenhagen opened on Monday with appeals for urgent action from the United Nations and from officials of countries endangered by warmer temperatures, rising sea levels and other damage such as melting glaciers.
As the climate meeting got under way on Tuesday morning, inside the vast blocks that make up the conference center, environmental groups already were chanting in favor of preservation of forests and handing out symbolic cardboard cutouts labeled as carbon dioxide in the central area.
Representatives from governments said there would be further ceremonial events before the hard negotiating begins, later on Tuesday.
A major reason that hopes have risen in recent weeks is the expectation that Mr. Obama — who plans to attend closing days of the conference next week — will formally commit the United States to making cuts in greenhouse gases. The United States declined to ratify the Kyoto Protocol, a previous agreement on curbing greenhouse gases, because of strong opposition in the Senate and from the Bush administration.
The refusal to ratify the Kyoto protocol has left a lingering mistrust of the United States in other parts of the world. The finding by the E.P.A. is expected to allow President 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 legislation.
Senator Barbara Boxer, Democrat of California and chairwoman of the Senate Environment and Public Works Committee, said that in light of the ruling, “the president’s appearance in Copenhagen will carry even more weight, because it shows that America is taking this issue very seriously and is moving forward.”
Over the next two weeks, the nations gathered in Copenhagen will try to reach what has so far been elusive common ground on the issue of climate change.
Delegates will try to hammer out some of the most vexing details attending the pursuit of a global climate deal. These include broad cuts in greenhouse gas emissions, particularly from big polluters like the United States and China, and a commitment from wealthy nations to deliver what could ultimately be hundreds of billions of dollars in financing to poor countries, which argue that they are ill equipped to deal with a problem they did little to create.
Several countries announced new emissions goals in the days leading to the meeting here, including China, Brazil, the United States and more recently India and South Africa. But many conference participants have noted that these commitments remain far too low to keep rising temperatures in check over coming decades.
The pledges so far are “not going to get us as far we need to go, to really stay within the two-degree limit,” Koko Warner, an observer with the United Nations University in Bonn, Germany, said Monday, referring to scientists’ recommendations that temperature increases be capped at two degrees Celsius (3.6 degrees Fahrenheit) above pre-industrial levels.
“We don’t want to admit it, because the consequences are so bad,” she said.
Tom Zeller Jr. contributed reporting from Copenhagen, and John M. Broder from Washington.
