NASA's chief climate scientist is in hot water with colleagues and at least one lawmaker after calling on citizens to engage in civil disobedience at what is being billed as the largest public protest of global warming ever in the United States.

In a video on, Dr. James Hansen is seen urging Americans to "take a stand on global warming" during the March 2 protest at the Capitol Power Plant in Southeast Washington, D.C.

"We need to send a message to Congress and the president that we want them to take the actions that are needed to preserve climate for young people and future generations and all life on the planet," says Hansen, who has likened coal-fired power plants to "factories of death" and claims he was muzzled by the Bush administration when he warned of drastic climate changes.

"What has become clear from the science is that we cannot burn all of the fossil fuels without creating a very different planet. The only practical way to solve the problem is to phase out the biggest source of carbon — and that's coal."

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But critics say Hansen's latest call to action blurs the line between astronomer and activist and may violate the Hatch Act, which prohibits federal employees from participating in partisan political activity.

"Oh my goodness," one of Hansen's former supervisors, Dr. John Theon, told when informed of the video. "I'm not surprised ... The fact that Jim Hansen has gone off the deep end here is sad because he's a good fellow."

Theon, a former senior NASA atmospheric scientist, rebuked Hansen last month in a letter to the Senate's Environment and Public Works Committee, saying Hansen had violated NASA's official position on climate forecasting without sufficient evidence and embarrassed the agency by airing his claims before Congress in 1988.

"Why he has not been fired I do not understand," Theon said. "As a civil servant, you can't participate in calling for a public demonstration. You may be able to participate as a private citizen, but when you go on the Internet and call for people to break the law, that's a problem."

Officials at the U.S. Office of Special Counsel, which investigates possible Hatch Act violations, disagreed, saying Hansen is in the clear since it's an "issue-oriented activity," according to Hatch Unit attorney Erica Stern Hamrick.

The majority of federal government employees are allowed to take an active part in political activities, while workers at other departments like the FBI, Secret Service and National Security Council are subject to more restrictions on their political activities.

NASA spokesman Mark Hess also defended Hansen.

"He's doing this as a private citizen on his own time and there's nothing wrong with that," Hess told "There's nothing partisan here. You don't give up your rights to free speech by becoming a government employee."

Matt Leonard, a project coordinator for Greenpeace, one of more than 90 organizations endorsing the protest, said several thousand people are expected to participate and "peacefully disrupt operations" at the plant just blocks from Capitol Hill.

Participants are willing to "put their bodies on the line to stop climate change," including risking arrest, Leonard said.

"Our intention is to completely surround the facility, basically sending a message that these types of power plants can't be a part of our future," Leonard said. "They're destroying our environment."

Hansen will be in attendance and is expected to speak at the "completely nonviolent, peaceful" protest, Leonard said.

Meanwhile, Rep. Dana Rohrabacher, R-Calif., urged Hansen to rethink his plans.

"If he wants to have a demonstration concerning global warming, coming to the Capitol is not a right choice," Rohrabacher told "The bottom line is if Hansen wants to protest global warming, he should go to the National Cathedral and take it up with God rather than going to Capitol Hill."

Rohrabacher, a member of the House's Committee on Science and Technology, called on Hansen to "step out" of his role.

"He obviously doesn't feel comfortable with the restraints that come with being a scientist rather than a political activist," Rohrabacher said. "Most of us have always thought he has been hiding behind a scientific facade, and really, he was a political activist all along."

Chris Horner, author of "Red Hot Lies: How Global Warming Alarmists Use Threats, Fraud, and Deception to Keep You Misinformed," also denounced Hansen's latest call to arms against climate change.

"He's providing ample cause to question his employment on the taxpayer dime," Horner told "He's clearly abused his platform provided to him by the taxpayer, principally by the way he's been exposed of manipulating and revising data with the strange coincidence of him always found on the side of exaggerating the warming."

Horner claimed that Hansen doctored temperature data on two occasions in 2001 and once in 2007 in attempts to show an impending climate catastrophe.

"He's creating an upward slope that really wasn't there," Horner said. "At some point you have to say these aren't mistakes."

Hansen, who did not respond to repeated requests for comment on this story, was most recently honored for his work last month with the 2009 Carl-Gustaf Rossby Research Medal, the highest honor bestowed by the American Meteorological Society.

"Jim Hansen is performing a tremendous job at communicating our science to the public and, more importantly, to policymakers and decision-makers," Franco Einaudi, director of the Earth Sciences Division at NASA's Goddard Space Flight Center, said in a press release.

"The debate about global change is often emotional and controversial, and Jim has had the courage to stand up and say what others did not want to hear. He has acquired a credibility that very few scientists have. His success is due in part to his personality, in part to his scientific achievements, and in part to his refusing to sit on the sidelines of the debate."

Former Vice President Al Gore, who toured with Hansen while promoting "An Inconvenient Truth," did not return repeated requests for comment for this article.