A Washington environmental group charged yesterday that three researchers who are outspoken critics of the scientific evidence for global warming have received hundreds of thousands of dollars from the petroleum and coal industries, and that this funding has influenced their views.

One of the scientists also regularly receives research funding from the government of Kuwait, a leading oil producer, according to the documents released yesterday by Ozone Action, an environmental group that lobbies on the issues of air quality and global climate change.

In interviews yesterday, two of the researchers, Robert Balling of Arizona State University and Patrick Michaels of the University of Virginia, acknowledged receiving research funding from the energy industry but disputed the charge that such funding biased their scientific findings to favor industry positions. The third researcher, Sherwood Idso of Phoenix, did not return two telephone calls for comment.

The researchers, frequently called to testify before congressional panels and other public groups, have raised questions about whether global warming is occurring. They also have suggested that if the phenomenon is real, it is generally caused by natural factors and not by the burning of fossil fuels and other human activities.

Balling, director of the climatology program at Arizona State, has received as much as $311,000 from the oil and coal industries and from Kuwait, according to the documents.

A large proportion of his funding came from the Cyprus Minerals Co., an Arizona-based organization composed of various petroleum and coal companies. He also received funding from the Kuwait Foundation for the Advancement of Sciences, a research institution funded by the Kuwaiti government.

Michaels, a professor at the University of Virginia, received about $150,000 from petroleum and coal interests, including the Western Fuels Association, an umbrella industry organization, the documents said. Michaels and Balling confirmed their funding sources in separate depositions before a Minnesota court last year. Balling and Michaels were invited two weeks ago by GOP lawmakers to make their case to the House Science Committee, which wants to cut by 40 percent federal funding for a program designed to monitor climate trends.

Idso, a Phoenix-based physicist who has worked closely with Balling, has received an undisclosed amount of funding from oil, gas and utility sources, according to Ozone Action.

"Shedding light on where these critics get their funding helps us to explain how industry is able to add confusion to the general sense that global warming is a problem and something should be done about it," said John Passacantando, executive director of Ozone Action. "Except for the fact that they get funding from the oil and coal industries, they would have no platform at all."

Michaels acknowledged that some of the climate change research he directs at the University of Virginia is funded by grants from the energy industry but stressed that the funding goes to the institution and not to him personally.

Any assertion that his funding sources bias him in favor of industry is "ludicrous," he said. "In fact, we receive 70 percent of funding from public and 30 percent from private concerns," he said. "By extension that would make my research 70 percent beholden to public interests and 30 percent to private interests."

Balling said he receives about $20,000 a year in speaking fees from oil and coal groups, and that he has received a total of about $200,000 in personal income from such groups over the past eight years. His research institution receives $150,000 or so annually from such sources, he added.

"Regardless of the source of the funding, {the research} is peer-reviewed by specialists and published in noted scientific journals," he said. "The system provides a good screening process for good research."

In published articles and speeches, Balling has argued that the trend in global warming is exaggerated by other scientists and that warming occurred at a much greater pace before there was extensive burning of fossil fuels. He also has said that if warming does occur, it would benefit the environment.