The heads of major fossil-fuel companies who spread disinformation about global warming should be "tried for high crimes against humanity and nature," according to a leading climate scientist.
Dr. James Hansen, director of the NASA Goddard Institute for Space Studies in New York, sounded the alarm about global warming in testimony before a Senate subcommittee exactly 20 years ago.
He returned to the topic Monday with a speech at the National Press Club in Washington, D.C., given to the Worldwatch Institute, before which he was called a hero by former Sen. Tim Wirth, D-Colo., who headed the 1988 hearing.
"Special interests have blocked the transition to our renewable energy future," Hansen writes in an opinion piece posted on the institute's Web site. "Instead of moving heavily into renewable energies, fossil fuel companies choose to spread doubt about global warming, just as tobacco companies discredited the link between smoking and cancer.
"Methods are sophisticated, including funding to help shape school textbook discussions of global warming," Hansen continues. "CEOs of fossil energy companies know what they are doing and are aware of the long-term consequences of continued business as usual. In my opinion, these CEOs should be tried for high crimes against humanity and nature."
• Click here to read Hansen's opinion piece on the Web site of the Worldwatch Institute.
Later in the day, Hansen appeared at an informal briefing on Capitol Hill with Rep. Ed Markey, D-Mass., head of the House Select Committee on Energy Independence and Global Warming.
Hansen told reporters and members of the public that the world has long passed the "dangerous level" for greenhouse gases in the atmosphere and needs to get back to 1988 levels.
He said Earth's atmosphere can only stay this loaded with man-made carbon dioxide for a couple more decades without changes such as mass extinction, ecosystem collapse and dramatic sea level rises.
"We're toast if we don't get on a very different path," said Hansen, who is sometimes called the godfather of global warming science, told The Associated Press. "This is the last chance."
Asked by a reporter about the feasibility of putting corporate CEOs on trial, Hansen dodged the question, stressing instead the need to take stronger measures against global warming.
• Click here to visit FOXNews.com's Natural Science Center.
To cut emissions, Hansen said coal-fired power plants that don't capture carbon dioxide emissions shouldn't be used in the United States after 2025, and should be eliminated in the rest of the world by 2030.
That carbon-capture technology is still being developed and not yet cost efficient for power plants.
Burning fossil fuels like coal is the chief cause of man-made greenhouse gases. Hansen said the Earth's atmosphere has got to get back to a level of 350 parts of carbon dioxide per million. Last month, it was 10 percent higher: 386.7 parts per million.
Hansen said he'll testify on behalf of British protesters against new coal-fired power plants. Protesters have chained themselves to gates and equipment at sites of several proposed coal plants in England.
"The thing that I think is most important is to block coal-fired power plants," Hansen told the luncheon. "I'm not yet at the point of chaining myself but we somehow have to draw attention to this."
Frank Maisano, a spokesman for many U.S. utilities, including those trying to build new coal plants, said while Hansen has shown foresight as a scientist, his "stop them all approach is very simplistic" and shows that he is beyond his level of expertise.
The year of Hansen's original testimony was the world's hottest year on record. Since then, 14 years have been hotter, according to the National Oceanic and Atmospheric Administration.
Two decades later, Hansen spent his time on the question of whether it's too late to do anything about it. His answer: There's still time to stop the worst, but not much time.
"We see a tipping point occurring right before our eyes," Hansen said during his appearance at the National Press Club. "The Arctic is the first tipping point and it's occurring exactly the way we said it would."
Hansen, echoing work by other scientists, said that in five to 10 years, the Arctic will be free of sea ice in the summer.
Longtime global-warming skeptic Sen. James Inhofe, R-Okla., citing a recent poll, said in a statement, "Hansen, [former Vice President] Gore and the media have been trumpeting man-made climate doom since the 1980s. But Americans are not buying it."
But Rep. Markey said, "Dr. Hansen was right. Twenty years later, we recognize him as a climate prophet."
The Associated Press contributed to this report.
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