He said he has not received any factual objections to the findings in the report, and said he is not aware of anyone who declined to sign the report because of factual objections.

Many of the Harvard scientists took particular issue with the Bush administration’s treatment of global warming. The UCS statement accuses the White House of demanding “extensive changes” to a report by the Environmental Protection Agency (EPA), leading the EPA to delete an entire section concerning the impact of human activity on climate change.

Chivian said the administration has interfered with progress in combating global warming.

“One of the major issues we work on is global warming and climate change, loss of biological diversity, and the administration has really stood in the way of policy progress by the Congress in supporting efforts to reduce effects of global warming and protect the ecosystem,” he said.

Lewis Branscomb, the former director of the National Bureau of Standards and a professor emeritus of science and public policy at the Kennedy School of Government, said he signed the report as “a matter of conscience,” but added that he expected it to have little effect on the White House.

“I don’t expect [the administration] to ask me for my advice any time soon,” he said.

—Staff writer Carol P. Choy can be reached at choy@fas.harvard.edu.