The administration has done nothing to punish Hansen since he made his public comments last fall, and Marburger said in an interview that he considers Hansen "a very good climate scientist" who should stick to scientific analysis instead of policy prescriptions.
"I take his work seriously. His work has had a big impact on this administration's climate-change policy," Marburger said. "But he's not an economist. The fact that he's a good scientist does not necessarily make him the best person to formulate policy that would affect the economy."
NASA's James E. Hansen denounced the Bush administration's policy on climate change in a speech last year in Iowa.
(Melanie Patterson -- Daily Iowan Via AP)
James E. Hansen
Title: Director, Goddard Institute for Space Studies.
Education: Bachelor's of science in physics and mathematics, University of Iowa; doctorate in physics, University of Iowa.
Family: Married; two children; two grandchildren.
Career highlights: Helped identify the properties of clouds that covered Venus so later researchers could determine the clouds were made of sulfuric acid; showed how scientists could use large volcanic eruptions to help predict climate change.
Recent reading: "Galileo's Mistake" by Wade Rowland and "Galileo in Rome" by William R. Shea and Mariano Artigas.
Pastimes: Teaching his grandchildren astronomy with his new telescope.
Civil Rights Commissioner Marches in Different Time (The Washington Post, Jan 17, 2005)
Spy-Turned-Author Looks Back At a CIA Mired in Bureaucracy (The Washington Post, Jan 14, 2005)
USAID Director Keeps an Eye on Long-Term Recovery (The Washington Post, Jan 6, 2005)
Looking Beyond Enforcement at the EPA (The Washington Post, Jan 4, 2005)
Guiding Disaster Aid In Post-Sept. 11 Era (The Washington Post, Dec 27, 2004)
Former vice president Al Gore, who backs limits on emissions of carbon dioxide, said the administration's strained relationship with Hansen shows the "contempt for the rule of reason" of Bush and his deputies.
"When science conflicts with the exercise of power, they attempt to demean the messenger attempting to deliver the truth, and they seek out self-interested advocates of alternative views of reality," said Gore, who as a senator defended Hansen during the controversy over his 1989 testimony.
Within the scientific community, Hansen remains respected for much of his research, though some have questioned his recent studies on the effect of aerosols on global warming. He is popular at the space institute -- housed at Columbia University above the famed diner from the comedy series "Seinfield" -- where he has played Frisbee in the halls.
Gavin A. Schmidt, a climatologist who has worked with Hansen at Goddard for nearly a decade, said Hansen gets his leverage from the fact that he a senior scholar who is still breaking scientific ground.
"Very few people have that kind of longevity and credibility and are still doing new things," Schmidt said. "Any time he says something, it's news. He still sets the agenda."
Kevin E. Trenberth, who heads the climate analysis section of the nonprofit, federally funded National Center for Atmospheric Research, said Hansen's willingness to espouse the dominant scientific view on climate change "is a responsible thing to do, even if it puts at potential jeopardy his own position." Trenberth added: "This is an important issue, a long-term issue that affects humanity in the future."
Some, however, have questioned Hansen's approach. Patrick J. Michaels, a climatologist and a senior fellow in environmental studies at the libertarian Cato Institute, said it was inappropriate for Hansen as a federal employee to attack the administration in a battleground state less than two weeks before the election.
"The problem with Jim is he does climate and then he makes policy decisions that I don't think are very thoughtful," said Michaels, who receives funding from public and industry sources, and opposes mandatory carbon controls.
Hansen has found some common ground with administration officials, who like his recent findings that curbing methane emissions from landfills, mining operations and gas-drilling ventures can help counter warming. The administration recently persuaded more than a dozen countries to sign a pact to capture methane before it is released into the atmosphere, a program Hansen praised.
But it remains unclear whether Bush officials can reach some sort of detente with Hansen, who said in a recent e-mail that he is not interested in "making the administration mad" but in persuading it to cut carbon dioxide emissions from power plants and elsewhere. But in the meantime, Hansen said he will continue to press ahead with both research and advocacy.
"You can't just give up," he said. "I remain optimistic, even in this administration, that the evidence is going to become strong enough so there's a chance there will be a change in policy."