But as one of the leading scientific experts and public Jeremiahs on the subject, the head of the National Aeronautics and Space Administration's Goddard Institute for Space Studies in New York has been in the thick of it for many years.
He heads a federal government research team that's butted heads with climate skeptics and sometimes with the Bush administration. Dr. Hansen, who writes prolifically, is often called to testify before Congress. And last week he was tossing rhetorical darts at the Houghton Mifflin publishing company for what he calls "many gross errors" in a textbook used in colleges and Advanced Placement high school classes.
One chapter, written by conservative authors, states that "science doesn't know how bad the greenhouse effect is" and that global warming is "enmeshed in scientific uncertainty." While that may be literally true, it doesn't reflect the expert consensus. As a Boston Globe story observed:
"While there are still some scientists who downplay global warming and the role of burning fossil fuels, the overwhelming majority of climate scientists ... say human activity is causing climate change. Last year an international collection of hundreds of scientists and government officials unanimously approved wording that said the scientific community had 'very high confidence,' meaning more than 90 percent likelihood, that global warming is caused by humans."
"I strongly urge that you update the textbook to reflect the broad consensus of the scientific community. Failure to correct the book's errors will leave students gravely misinformed about the facts and science of global warming, one of the most serious problems that we as a society and as a species face."
As an outspoken scientist who warns that the earth already has a dangerous level of carbon dioxide in the atmosphere, Hansen naturally has his critics.
At a recent conference of climate-change skeptics in New York sponsored by the conservative Heartland Institute, William Gray, a retired professor of atmospheric science at Colorado State University in Fort Collins, predicted that the earth would experience a cooling period in 10 years.
A reporter for conservative watchdog group Business & Media Institute wrote:
"[Gray] said the models Hansen used to forecast drastic increases in the earth's temperature due to carbon in the atmosphere were flawed because they included too much water vapor, the most abundant greenhouse gas.
" '[S]o he puts that much vapor in his model and of course he gets this,' Gray said. 'He must get upper troposphere, where the temperature is seven degrees warmer for a doubl[ing of] CO2. Well, the reason he got that was – why this upper-level warming was there – was he put too much water vapor in the model.' "
Such critics do not dampen Hansen's dogged effort to reverse current temperature trends caused by heat-trapping greenhouse gases like carbon dioxide, which Hansen warns has reached the "tipping point" of 385 parts per million. As noted by news organization Agence France-Presse:
"In a paper he [recently submitted] to Science magazine ..., Hansen calls for phasing out all coal-fired plants by 2030, taxing their emissions until then, and banning the building of new plants unless they are designed to trap and segregate the carbon dioxide they emit.
"The major obstacle to saving the planet from its inhabitants is not technology, insisted Hansen, named one of the world's 100 most influential people in 2006 by Time magazine.
" 'The problem is that 90 percent of energy is fossil fuels. And that is such a huge business, it has permeated our government,' he maintained."
Claiming in the AFP article that "both the executive branch and the legislative branch are strongly influenced by special fossil fuel interests," Hansen is challenging those interests directly.
He recently wrote to the head of one of the nation's largest power companies, asking that they meet to discuss the role coal-fired plants play in global warming. A Washington Post article went on to say that:
"... James E. Rogers of Duke Energy accepted Hansen's invitation, though he made it clear he does not foresee calling off plans to build more of the power plants that Hansen considers a main culprit in climate change.
"The exchange, carried out in full public view, highlights both a recent shift in the climate debate and the difficulty of translating this change into concrete action…. 'We simply cannot burn the coal and put the CO2 in the atmosphere and avoid having serious changes in the atmosphere,' [Hansen] said. 'The scientists are beginning to realize we have to have a much more dramatic change in direction.'"