The White House selectively made several hundred changes in scientific reports to exaggerate uncertainty about the human contribution to global warming, a House committee reported Monday, citing newly released administration documents.

The House Oversight and Government Reform Committee released its first findings in a months-long investigation into allegations the Bush administration doctored scientific evidence about global warming. The panel’s Democratic majority pointed to hundreds of changes recommended to several reports on global warming prepared in 2003.

Chairman Henry A. Waxman, D-Calif., said the first eight boxes of documents the panel received since its initial hearing in January suggest “serious abuse” by White House officials. Waxman said science alone should drive policy decisions on global warming.

“If the administration turned this principle upside down with raw political pressure, it would put our country on a dangerous course,” Waxman said.

He added that it is “too early in the investigation to draw firm conclusions” about whether the Bush administration interfered with climate research and muzzled scientists from speaking to the press.

Committee Republicans criticized the panel’s findings, claiming they overplay the White House role in routine interagency reviews.

The Monday hearing kicked off a busy week of activity in Congress surrounding the climate-change debate, as Democrats work to build momentum for legislation that would mandate a cap on greenhouse gas emissions. A climate-change rally is expected to draw thousands of demonstrators to Capitol Hill Tuesday; on Wednesday, former Vice President Al Gore brings his Oscar-winning global warming road show to House and Senate hearings.

The Bush administration opposes mandatory restrictions on industrial emissions of carbon dioxide and other greenhouse gases.

The panel heard testimony Monday from former White House official Philip A. Cooney, who played a central role in the controversy while serving as chief of staff for the White House Council on Environmental Quality from 2001-2005.

Committee Democrats accused Cooney — a non-scientist who now works for Exxon Mobil Corp. and worked for the American Petroleum Institute before joining the administration — of doing the oil industry’s bidding by toning down the reports’ scientific assertions about global warming. The panel released e-mails, handwritten notes and typed comments by Cooney and other administration officials requesting changes.

For instance, Cooney recommended removing the phrase “the 1990s are likely to have been the warmest decade in the past 1,000 years for the Northern Hemisphere” from a 2003 EPA report. In the same paragraph, he recommended adding: “The Earth’s climate has changed dramatically throughout history and will continue to change due to natural variability.”

Cooney testified that he requested no changes to “99 percent” of material crossing his desk, and he said all the revisions he suggested were guided by a 2001 policy speech by President Bush on research priorities and a National Academy of Sciences report on climate-change science.

Cooney, who submitted to hours of private questioning by committee attorneys last week, said none of the edits by the White House misstated any fact and that even the academy reported that “large uncertainties in projections of future climate” needed to be addressed.

But Democrats pointed out that Cooney recommended striking a sentence in the 2003 EPA report that said the academy concluded greenhouse gases were increasing and the world’s climate was getting warmer because of humans.

Instead, Cooney suggested using the sentence: “Some activities emit greenhouse gases and other substances that directly or indirectly may affect the balance of incoming and outgoing radiation, thereby potentially affecting climate on regional and global scales.”

Cooney said he could not recall the source of his information but wanted to include a more comprehensive sentence in the report.

Republicans on the committee defended Cooney, a lawyer, saying that his work experience did not necessarily mean he was favoring the oil industry’s views while serving in the White House.

“I have no loyalty to car alarms, and no animosity to car thieves that exist in Washington today,” said Darrell Issa, R-Calif., who owned a car alarm company before he was elected to the House in 2000. “I’ve moved on.”