Story highlights
• Chairman said officials mislead by "injecting doubt" into global warming science
• House panel looking for evidence of political pressure on government scientists
• Advocacy groups says half of scientists told to delete material from reports
• Sens. McCain, Obama to express views on global warming at hearing


_{Scientists believe global warming is causing the polar ice caps to melt, raising ocean levels and threatening coastal regions.}

WASHINGTON (AP) -- The Democratic chairman of a House panel examining the government's response to climate change said Tuesday there is evidence that senior Bush administration officials sought repeatedly "to mislead the public by injecting doubt into the science of global warming."

Rep. Henry Waxman, D-California, said he and the top Republican on his oversight committee, Rep. Tom Davis of Virginia, have sought documents from the administration on climate policy, but repeatedly been rebuffed.

"The committee isn't trying to obtain state secrets or documents that could affect our immediate national security," said Waxman, opening the hearing. "We are simply seeking answers to whether the White House's political staff is inappropriately censoring impartial government scientists."

"We know that the White House possesses documents that contain evidence of an attempt by senior administration officials to mislead the public by injecting doubt into the science of global warming and minimize the potential danger," Waxman said.

Administration officials were not scheduled to testify before the House Oversight and Government Reform Committee. In the past the White House has said it has only sought to inject balance into reports on climate change. Present Bush has acknowledged concerns about global warming, but strongly opposes mandatory caps of greenhouse gas emissions, arguing that approach would be too costly.

Waxman said his committee had not received documents it requested from the White House and other agencies, and that a handful of papers received on the eve of the hearing "add nothing to our inquiry."

Two private advocacy groups, meanwhile, presented to the panel a survey of government climate scientists showing that many of them say they have been subjected to political pressure aimed at downplaying the threat of global warming.

Survey: Scientists pressured to downplay threat

The groups presented a survey that shows two in five of the 279 climate scientists who responded to a questionnaire complained that some of their scientific papers had been edited in a way that changed their meaning. Nearly half of the 279 said in response to another question that at some point they had been told to delete reference to "global warming" or "climate change" from a report.

The questionnaire was sent by the Union of Concerned Scientists, a private advocacy group. The report also was based on "firsthand experiences" described in interviews with the Government Accountability Project, which helps government whistleblowers, lawmakers were told.

At the same time, Sen. Barbara Boxer, D-California, sought to gauge her colleague's sentiment on climate change. She opened a meeting where senators were to express their views on global warming in advance of a broader set of hearings on the issue.

Among those scheduled to make comments were two presidential hopefuls -- Sens. John McCain, R-Arizona, and Barack Obama, D-Illinois. Both lawmakers favor mandatory reductions in greenhouse gas emissions, something opposed by President Bush, who argues such requirements would threaten economic growth.

U.N. climate change report expected soon

The intense interest about climate change comes as some 500 climate scientists gather in Paris this week to put the final touches on a United Nations report on how warming, as a result of a growing concentration of heat-trapping gases in the atmosphere, is likely to affect sea levels.

They agree sea levels will rise, but not on how much. Whatever the report says when it comes out at week's end, it is likely to influence the climate debate in Congress.

At the Waxman hearing, the two advocacy groups said their research -- based on the questionnaires, interviews and documents obtained through the Freedom of Information Act -- revealed "evidence of widespread interference in climate science in federal agencies."

The groups report described largely anonymous claims by scientists that their findings at times at been misrepresented, that they had been pressured to change findings and had been restricted on what they were allowed to say publicly.

The survey involved scientists across the government from NASA and the Environmental Protection Agency to the department's of Agriculture, Energy, Commerce, Defense and Interior. In all the government employees more than 2,000 scientists who spend at least some of their time on climate issues, the report said.

Copyright 2007 The Associated Press.