Turning Up the Heat on Climate Issue

He told the sweltering senators that 1988 was shaping up to be the warmest year in recorded history, and that -- with heat-trapping gases building up in the atmosphere -- this was probably not a coincidence.

"The greenhouse effect has been detected, and it is changing our climate now," Hansen said, according to a Washington Post account of the hearing. "We already reached the point where the greenhouse effect is important."

Christopher Flavin of the Worldwatch Institute said Hansen's testimony made a crucial point: that rising temperatures were a problem for the present, not just for future generations.

"Until there was some evidence that it was actually happening, it was virtually impossible to motivate anyone," said Flavin, whose group is hosting Hansen's lunchtime speech today. "That will really sort of go down in history as a kind of pivot point."

Two decades later, climate change has become a global cause. Last year, the United Nations Intergovernmental Panel on Climate Change -- a collaboration of scientists from around the world -- won the Nobel Peace Prize for research establishing a consensus that the phenomenon is real. The panel shared the prize with former vice president Al Gore, who was recognized for his film "An Inconvenient Truth."

But things look different on Capitol Hill. In the two decades since Hansen's testimony, Congress has not passed any law mandating major cuts in greenhouse-gas emissions. In that interval, 21 new coal-fired generating units have been built at power plants around the United States. The country's total emissions of carbon dioxide have climbed by about 18 percent, according to the latest statistics.

The most recent attempt to pass a law, sponsored by Sens. Joseph I. Lieberman (I-Conn.) and John W. Warner (R-Va.), was pulled from the Senate floor June 6, after its supporters could not muster the votes to overcome a filibuster threat.

Opponents of the bill said that it would impose huge costs on the U.S. economy by raising fuel prices and that it would deliver only uncertain results.

In an e-mailed statement, Sen. James M. Inhofe (R-Okla.) said the bill's failure was proof that Hansen's message had not caught on.

"Hansen, Gore, and the media have been trumpeting man-made climate doom since the 1980s. But Americans are not buying it," Inhofe said. "It's back to the drawing board for Hansen and company as the alleged 'consensus' over man-made climate fears continues to wane and more and more scientists declare their dissent."

Today, Hansen said, he intends to repeat his message from two decades ago -- this time with even more urgency. He said he believes that the United States must wean itself almost totally off fossil fuels, and do it as quickly as possible, to stave off the most catastrophic consequences of warming.

"We're at the situation again when there's this big gap between what we understand scientifically and what is known, recognized by the public and policymakers," he said. "This time, we have to close that gap in a hurry, because we're running out of time."

This time, though, the weather won't help as much. The high for today is supposed to be only in the low 80s.

Staff writer Joel Achenbach contributed to this report.