Global warming is "very likely" a human-caused problem that will last for centuries and require concerted international action to reduce its potentially devastating impacts, a United Nations panel of climate experts declared Friday in a landmark report. Now the question is whether the bleak report will change the politics of global warming in the U.S. and lead to a more united effort to deal with the problem, and for the moment, that appears uncertain.
The Bush administration embraced the report but rejected demands for a mandatory system of capping "greenhouse gas" emissions such as carbon dioxide. Instead, the administration said President Bush would rely on his plans to develop more renewable fuel and require more efficient vehicles.
But with Democrats controlling Congress, pressure is apt to build on the White House to take a tougher approach. More than half a dozen bills--some of them bipartisan--have been presented to Congress calling for mandatory caps on emissions, though the administration said they would hurt the economy and not effectively deal with the problem.
Senate Democratic Leader Harry Reid of Nevada said, "President Bush should immediately work with Congress to pass legislation that requires reductions in the emissions of greenhouse gases, and he should call together the leaders of the world to obtain their binding commitment to reducing pollution around the globe."
The report by the UN's Intergovernmental Panel on Climate Change struck a chord of urgency as it warned of rising sea levels, more powerful storms and rapidly shifting weather patterns, including floods and droughts, resulting from a warming of the planet that it said could last a thousand years.
The scientists from 113 countries said they are now 90 percent confident that global warming is caused by humans, in contrast with a 2001 report in which they said they were 60 percent to 90 percent confident.
Achim Steiner, executive director of the UN Environment Program, said the focus should shift from the cause of global warming "to what on Earth are we going to do about it. The public should not sit back and say, `There's nothing we can do.'"
"Warming of the planet is unequivocal," the 21-page report concluded, "as is now evident from observations of global average air and ocean temperatures, widespread melting of snow and ice, and rising global mean sea level."
In effect, the panel said governments and people cannot prevent the planet from warming but that steps can be taken to stem the projected increases.
The panel forecast global temperature increases of 2 to 11.5 degrees Fahrenheit by the year 2100 but added that its best estimate was for a rise of 3.2 to 7.1 degrees. Warming during the 21st Century would "very likely be larger" than that of the 20th Century, the report said.
Not all scientists agree
Some question such conclusions about global warming.
Patrick Michaels, a scholar at the Cato Institute, a Washington libertarian think tank, said that "it is not news to say that human beings are responsible for much of the warming in the late 20th Century."
But Michaels said the report was not as alarming as portrayed. He cited a prediction by the panel that sea levels would rise by a modest 7 to 23 inches by the end of the century and noted that this was slightly less than the panel reported in 2001.
"What this report does is place this very small but very widely quoted group of alarmists--who are talking about 20 feet of sea-rise--far, far beyond the fringes [of environmental science]," he said.
But the report, as well as Bush administration officials, said the relatively modest increases in the sea level do not take into account the recent increased rate of ice melting in Greenland and Antarctica.
"[The sea-rise prediction in the report] is less," Stephen Johnson, administrator of the Environmental Protection Agency, told reporters. "But we believe there are other effects that haven't been taken into account yet."
The report said an additional 3.9 to 7.98 inches of sea-level rise are possible if the recent melting of polar ice sheets continues at its recent rate.
Joseph Romm, an assistant secretary of energy in the Clinton administration, said in an interview that if the rate of recent ice loss from Greenland and Antarctica continues, there would be a dramatic rise in sea levels that would devastate coastlines around the world.
Romm, author of a book on global warming, called the report "very solid and alarming." He said a "hidden bombshell" in the report is a finding that as the Earth grows hotter, the less the soil is able to absorb carbon. That would lead to an acceleration of greenhouse gases, he said, and could be devastating to the ecosystem.
"The key point is that it said humans are the most likely cause," Romm said. "If we are the main cause, we are the main solution. You can't endorse the report and not endorse strong action on climate change."
The Bush administration said it is already taking action. The White House noted that Bush has devoted nearly $29 billion to climate-related science, technology, international assistance and incentives since 2001.
Bush has spent nearly $9 billion on climate science research, "leading the world with unparalleled financial commitment," the White House said in a statement.
In his State of the Union speech last month, the president acknowledged that global warming is a problem and that he is taking steps to do something about it. But it has not been his top priority.
He refused to endorse the 1997 Kyoto agreement to create a mandatory system to cap carbon dioxide emissions, saying it would harm the U.S. economy and wouldn't be effective because fast-developing countries like China and India are not abiding by it.
During his first presidential campaign, he had pledged to regulate carbon dioxide emissions under the Clean Air Act, but he backtracked when he took office.
At the Energy Department on Friday, Secretary Samuel Bodman said the president has set an "aggressive" goal to cut greenhouse gas emissions by 18 percent by 2012, through increasing the supply of renewable fuels like ethanol and reforming the government's fuel economy standards for cars.
Bodman also called for a dramatic increase in nuclear power generation around the world.