In the four years since President Bush took office, scientific sleuths trying to understand the extent of global climate change — and finger the culprits — have come up with several important new clues:
• Glaciers in the Antarctic and in Greenland are melting much faster than expected, and the fastest moving glacier in the world has doubled its speed.
• Worldwide, plants are blooming several days earlier than they did a decade ago, and animals are migrating toward cooler climates across the globe.
• The oceans have absorbed extra heat trapped in the atmosphere, which indicates Earth's temperature should rise by another degree Fahrenheit in the coming decades.
The president's scientific and policy advisers on global warming do not dispute these findings, but none of them has persuaded the White House to alter its current climate policy. Rather than endorsing mandatory limits on carbon dioxide emissions linked to warming, the course embraced by most of America's allies, the White House is focusing on technological fixes: developing energy sources that burn cleaner or finding ways to extract excess carbon dioxide out of the atmosphere.
"Our approach is founded on sound science, and on trying to address, with different strategies, climate change," said Paula J. Dobriansky, undersecretary of state for global affairs.
Race to catch up
International negotiators are to embark on a new round of climate talks tomorrow as researchers are still struggling with how to measure the effects of global warming and to predict what's in store.
"We're learning fast, but part of what we're learning is the climate system is really complicated. ... I don't think we'll ever make the kind of prediction Bush would want," said Wallace S. Broecker, a geochemist at Columbia's Lamont-Doherty Earth Observatory. Broecker believes the United States has to act quickly to counter its contribution to global warming. "If we don't pick up the pace, we're not going to get there."
The United States is taking part in the Buenos Aires talks even though the administration opted out of the Kyoto Protocol, which will restrict carbon emissions in most industrialized nations starting in 2008. Dobriansky said U.S. officials will try to convince their counterparts that technological change, not government mandates, offers the best chance to preserve both economic growth and the environment.
Critics say Bush ignoring science
As a candidate in 2000, Bush flirted with the idea of limiting carbon dioxide emissions, but he dismissed that option during his first year in office, saying that "given the limits of our knowledge," the nation was better off focusing on voluntary emissions reductions and better energy sources. To that end, the administration has poured nearly $8 billion into climate change research since 2001.
James R. Mahoney, who oversees this research as assistant secretary of commerce for oceans and atmosphere, said even though researchers have refined computer models, helped design a more sweeping global observation system and improved the world's overall knowledge of global warming, "We continue to be humbled in the limits of our own knowledge. ... It's a daunting challenge."
But some of the government's own scientists, as well as many independent researchers, reject this assessment. James E. Hansen, who directs NASA's Goddard Institute for Space Studies, told a University of Iowa audience in October that the administration is ignoring evidence of "dangerous anthropogenic interference" with the climate. "Anthropogenic" means human-caused, and his phrasing is significant because the United States pledged in 1992, as part of an agreement called the U.N. Framework Convention on Climate Change, to take all necessary steps to combat such interference.
"As the evidence gathers, you would hope they would be flexible," Hansen said of the administration in an interview. "You can't wait another decade" to cut carbon dioxide emissions, he added.
Knowledge being honed
Hansen and other proponents of restricting greenhouse gases point to several recent studies that make the case for immediate action. These include a paper this year showing that ocean heat storage — which reflects the difference between the energy the earth receives from the sun and the heat it emits back into space — rose between 1993 and 2003 at a rate that conforms to current climate models. It also indicates that global temperatures will rise by 1 degree Fahrenheit over the next several decades.
Scientists have also refined their understanding of other factors that could accelerate or temper climate change. At one point, researchers thought warming would cause more water to evaporate and form clouds, which cool the atmosphere. They recently discovered this was not the case. They also have begun to grasp the complex role that aerosols — the fine particles emitted by cars, power plants and other sources — play. Lighter-colored aerosols, such as car exhaust and power plant pollution, reflect sunlight and have a cooling effect, while darker ones, such as soot, absorb it. Both types of emissions will affect warming in the future, though scientists are still gauging their influence.
Other researchers have documented concrete indications of global warming's effects, such as these: Plants worldwide are blooming an average 5.2 days earlier per decade, according to Stanford University senior fellow Terry L. Root; and the opossum, an animal that confined its range to the South as recently as the Civil War, can now be found as far north as Ontario.
When all these indicators "line up in the same direction, what's the possibility that's all an accident?" asked Stephen H. Schneider, who co-directs Stanford University's Center for Environmental Science and Policy and advocates stricter carbon limits.
Debate heats up
But some scientists do question the evidence. John R. Christy, an atmospheric science professor at the University of Alabama in Huntsville, said that despite a recent study suggesting the Arctic is warming much faster than the rest of the globe, the hottest years for Arctic temperatures in recorded history are 1937 and 1938, and current Greenland temperatures are not higher than they were 75 years ago. And Myron Ebell, who directs global warming and international environmental policy for the free-market Competitive Enterprise Institute, said some studies cast doubt on a U.N. pronouncement in 2001 that the 20th century was likely the warmest in a millennium.
Christy said, given the economic costs of imposing tighter controls on energy production, "The Bush administration is doing a more reasonable approach, considering that mandating carbon restrictions will have no measurable effect on what the climate will do."
Several senior administration officials said that while they agree that greenhouse gases such as carbon dioxide contribute to climate change, restricting these emissions right now would cost jobs. Instead, they said, the government should continue to focus its efforts on promoting technologies that will curb pollution. One example is FutureGen, a $1 billion, decade-long power plant project to convert coal into gas and store carbon emissions underground. Bush has also sponsored a $1.7 billion, five-year hydrogen car project aimed at eliminating carbon dioxide emissions from cars.
"The U.S. position is maybe the only rational position, to identify and promulgate application of new technologies," said White House science adviser John H. Marburger III. "To do anything meaningful [on limiting greenhouse gas emissions] requires a dramatic cessation or reduction of economic activity. It's simply not practical at the present time."
Advocates for CO2 limits see hope
Advocates of limiting greenhouse gases, however, remain optimistic they will eventually prevail. Christine Todd Whitman, former Environmental Protection Agency administrator in Bush's first term, said mandatory carbon dioxide reductions are "going to happen at some point," in part because multinational corporations will demand that U.S. policy mirror European standards.
Larry J. Schweiger, president of National Wildlife Federation, said Bush has an opportunity to outline a new climate policy in his second term.
"If President Bush personally sits down with the scientists and hears what has happened since he first came to office, we can work together to make progress on global warming," he said. "The president has an opportunity to leave behind a strong legacy of addressing one of the biggest challenges the world has ever faced. He shouldn't squander that opportunity."