In handwritten notes on drafts of several reports issued in 2002 and 2003, the official, Philip A. Cooney, removed or adjusted descriptions of climate research that government scientists and their supervisors, including some senior Bush administration officials, had already approved.

Mr. Cooney is chief of staff for the White House Council on Environmental Quality, the office that helps devise and promote administration policies on environmental issues. Before coming to the White House in 2001, he was the "climate team leader" and a lobbyist at the American Petroleum Institute, the largest trade group representing the interests of the oil industry. A lawyer with a bachelor's degree in economics, he has no scientific training.

The documents were obtained by The New York Times from the Government Accountability Project, a nonprofit legal-assistance group for government whistle-blowers. The project is representing Rick S. Piltz, who resigned in March after a decade working in the office that coordinates government climate research and issued the documents that Mr. Cooney edited.

A White House spokeswoman, Michele St. Martin, said today that Mr. Cooney would not be made available to comment. "We don't put Phil Cooney on the record," she said. "He's not a cleared spokesman."

Other White House officials said today that the changes made by Mr. Cooney were part of the normal interagency review that takes place on all documents related to global environmental change. "All comments are reviewed, and some are accepted and some are rejected," said Robert Hopkins, a spokesman for the White House Office of Science and Technology Policy. He noted that one of the reports Mr. Cooney worked on, the administration's 10-year plan for climate research, was strongly endorsed by the National Academy of Sciences.

And Myron Ebell, who has long campaigned against limits on greenhouse gases as director of climate policy at the Competitive Enterprise Institute, a libertarian group, said such editing was necessary for "consistency" in meshing programs with policy.

But critics said that while all administrations routinely vet government reports, scientific content in such reports should be reviewed by the White House Science and Technology Office. Climate experts and representatives of environmental groups, when shown examples of the revisions, said they illustrated the significant if largely invisible influence of Mr. Cooney and other White House officials with ties to energy industries that have long fought greenhouse-gas restrictions.

In a memo sent last week to the top officials dealing with climate change at a dozen agencies, Mr. Piltz said the White House editing and other actions threatened to taint the government's $1.8 billion-a-year effort to clarify the causes and consequences of climate change.

"Each administration has a policy position on climate change," Mr. Piltz wrote. "But I have not seen a situation like the one that has developed under this administration during the past four years, in which politicization by the White House has fed back directly into the science program in such as way as to undermine the credibility and integrity of the program."

A senior Environmental Protection Agency scientist who works on climate questions said the White House environmental council, where Mr. Cooney works, had offered valuable suggestions on reports on occasion. But the scientist, who spoke on the condition of anonymity because all agency employees are forbidden to speak with reporters without clearance, said the kinds of changes made by Mr. Cooney had damaged morale.

"I have colleagues in other agencies who express the same view, that it has somewhat of a chilling effect and has created a sense of frustration," he said.

Efforts by the Bush administration to highlight uncertainties in science pointing to human-caused warming appear to be putting the United States increasingly at odds with a growing list of world leaders and scientific bodies.

Prime Minister Tony Blair of Britain, who met with President Bush at the White House today, has been trying for several months to persuade Mr. Bush to intensify American efforts to limit greenhouse gases.

Mr. Bush has called only for voluntary measures to slow growth in emissions through 2012.

Today, saying their goal was to influence that meeting, the scientific academies of 11 countries, including those of the United States and Britain, released a joint letter saying "the scientific understanding of climate change is now sufficiently clear to justify nations taking prompt action."

Starting with the negotiations leading to the Kyoto Protocol climate treaty in 1997, the oil group has promoted the idea that uncertainties in climate science justify delaying emissions restrictions on carbon dioxide and other heat-trapping smokestack and tailpipe gases.

The top international and American panels of experts on climate have concluded that such emissions have very likely caused most of a global warming trend since 1950 and could raise temperatures at more than triple the 20th-century rate in this century if emissions are not cut.

Upon learning of the White House report revisions, representatives of some environmental groups said that the effort to amplify uncertainties in the science was clearly intended to delay consideration of limits on the gases, which remain an unavoidable byproduct of burning oil and coal. "They've got three more years and the only way to control this issue and do nothing about it is to muddy the science," said Eileen Claussen, the president of the Pew Center on Global Climate Change, a private group that has enlisted businesses in programs cutting emissions.

The alterations are sometimes as subtle as the insertion of an adjective, but cause a clear shift in the meaning of the documents.

For example, a sentence in an October 2002 draft of a regularly published summary of government climate research, "Our Changing Planet," originally read: "Many scientific observations indicate that the Earth is undergoing a period of relatively rapid change...."

Mr. Cooney's neat, compact notes modified the sentence to read: "Many scientific observations point to the conclusion that the Earth may be undergoing a period of relatively rapid change...."

In places where uncertainties in climate research were described, Mr. Cooney added qualifiers like "significant" and "fundamental."

Another document showing the same pattern of changes is the 2003 Strategic Plan for the United States Climate Change Science Program, a thick report describing the reorganization of government climate research that was requested by Mr. Bush in his first speech on the issue, in June 2001.

That document was reviewed by an expert panel assembled in 2003 by the National Academy of Sciences. The scientists largely endorsed the administration's research plan, but they warned that the administration's procedures for vetting reports on climate could result in excessive political interference with science.

Now it appeared that some interference was happening even before the research had gotten into full swing, said Dr. William H. Schlesinger, who was on the review committee and is dean of the Nicholas School of the Environment and Earth Sciences at Duke University.

After some of Mr. Cooney's changes to the drafts were described to Dr. Schlesinger by The New York Times, he said several seemed "egregious."

"They're trying to throw enough uncertainty in so that either policymakers or the public would not want to take a firm stand on it," he said.