Among those testifying yesterday was an atmospheric scientist who disavowed his own written testimony because it was altered by the Office of Management and Budget. The White House confirmed a report in the New York Times that an OMB official altered testimony by James E. Hansen, director of NASA's Goddard Institute for Space Studies, to avoid the impression "that there is unanimity within the government on this issue."

Global warming, caused by a buildup of carbon dioxide, methane and other gases, has emerged as a major environmental issue with worldwide implications. The gases are trapping more heat near the Earth, like a greenhouse, and posing the threat of climate change, intensified storms and the inundation of coastal areas as oceans rise.

"I'm suggesting that the warming of the Earth is increasing the decay of organic matter in the Earth," [George M. Woodwell] said. "It may be mobilizing carbon from the Earth, and that has not been worked into the climatologists' models."