NASA initiated damage control Thursday as it tried to clarify remarks made earlier in the day by the space agency's administrator, who told a national radio audience that he doubted whether global warming was really a problem.

Administrator Michael D. Griffin's comments came just hours before President Bush called on 15 nations to set greenhouse-gas emission standards, an effort that Griffin's comments implied might be useless.

"I have no doubt that global — that a trend of global warming exists," Griffin told National Public Radio's Morning Edition in an interview aired early Thursday. "I am not sure that it is fair to say that it is a problem we must wrestle with."

• Click here to listen to Griffin's comments.

"To assume that it is a problem is to assume that the state of Earth's climate today is the optimal climate, the best climate that we could have or ever have had, and that we need to take steps to make sure that it doesn't change," Griffin said.

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But Griffin, who heads an agency with a $16.5 billion budget, wondered whether global warming was an issue that needed to be grappled with at all.

"First of all, I don't think it's within the power of human beings to assure that the climate does not change, as millions of years of history have shown," he continued. "And second of all, I guess I would ask which human beings — where and when — are to be accorded the privilege of deciding that this particular climate that we have right here today, right now is the best climate for all other human beings. I think that's a rather arrogant position for people to take."

One of NASA's duties is charting global climate change.

"Nowhere in NASA's authorization, which of course governs what we do, is there anything at all telling us that we should take actions to affect climate change in either one way or another," Griffin told NPR. "We study global climate change — that is in our authorization. We think we do it rather well. I'm proud of that, but NASA is not an agency chartered to, quote, battle climate change."

In a telephone interview with LiveScience.com, NASA chief spokesman David Mould clarified that while NASA collects and analyzes data pertaining to global warming, it does not set policy. He told the Houston Chronicle that Griffin was simply attempting to characterize the agency's role in assessing environmental issues.

• Click here to read the LiveScience.com story.

Along the same lines, Griffin said in a press release Thursday after the interview aired:

"NASA is the world's preeminent organization in the study of Earth and the conditions that contribute to climate change and global warming. The agency is responsible for collecting data that is used by the science community and policy makers as part of an ongoing discussion regarding our planet's evolving systems.

"It is NASA's responsibility to collect, analyze and release information. It is not NASA's mission to make policy regarding possible climate change mitigation strategies. As I stated in the NPR interview, we are proud of our role and I believe we do it well."

Dr. Gavin A. Schmidt, a climate-change specialist at NASA's Goddard Institute for Space Studies in New York, was less charitable to his agency head's remarks.

"Griffin's comments seem surprisingly naive," Schmidt wrote in an e-mail to LiveScience.com. "We are not in a situation where we are shopping around for an ideal climate, but that we have adapted to the climate we have, and that therefore large changes to it are not likely to be beneficial."

Bush delivered his remarks to the U.S. Global Leadership Campaign at the Ronald Reagan Building and International Trade Center in Washington, D.C., ahead of his Group of Eight summit in Germany next week..

"The United States has taken the lead and that's the message I'm going to take to the G-8," Bush said.

Griffin, an aerospace engineer by training, may hold views contrary to many NASA staffers. Astrophysicist James E. Hansen, head of the Goddard Institute for Space Studies, testified to Congress about impending human-caused climate change in the 1980s, and more recently accused the Bush administration of trying to prevent him from speaking out about the issue.

Earlier this week, data collected by NASA satellites was released indicating that Greenland had experienced 10 more days of active snowmelt in the summer of 2006 than the average for the previous two decades.

Germany, the current president of the G-8 nations, earlier this week offered a proposal that would lower emissions to 50 percent below 1990 levels by 2050. Bush rejected that approach in favor of autumn meetings to set target standards.