NASA's top climate scientist has accused the Bush administration of trying to stop him from speaking out after he called in a lecture for swift cuts in emissions of the greenhouse gases linked to global warming.

James Hansen, director of the US space agency's Goddard Institute for Space Studies, said that officials at NASA headquarters had ordered the public affairs staff to review his forthcoming lectures, papers, postings on the Goddard website and requests for media interviews, the New York Times reported Sunday.

"They feel their job is to be this censor of information going out to the public," said Hansen, who told the paper he would ignore the restrictions. Dean Acosta, deputy assistant administrator for public affairs at NASA, denied to the Times that there was any effort to silence Hansen.

"That's not the way we operate here at NASA," Acosta said. "We promote openness and we speak with the facts." Acosta said that government scientists were free to discuss scientific findings but that policy statements should be left to policy makers and appointed spokesmen.

"This is not about any individual or any issue like global warming," he told the Times. "It's about coordination."

"Since 1988, (Hansen) has been issuing public warnings about the long-term threat from heat-trapping emissions, dominated by carbon dioxide, that are an unavoidable byproduct of burning coal, oil and other fossil fuels. He has had run-ins with politicians or their appointees in various administrations, including budget watchers in the first Bush administration and Vice President Al Gore," the Times reported. Hansen told the Times that "efforts to quiet him" had begun in a series of calls after a lecture he gave on December 6, 2005, at the annual meeting of the American Geophysical Union in San Francisco.

"In the talk, he said that significant emission cuts could be achieved with existing technologies, particularly in the case of motor vehicles, and that without leadership by the United States, climate change would eventually leave the earth 'a different planet'," the Times said. US administration policy is to use voluntary measures to slow, but not reverse, the growth of emissions.

"After that speech and the release of data by Dr Hansen on December 15 showing that 2005 was probably the warmest year in at least a century, officials at the headquarters of the space agency repeatedly phoned public affairs officers, who relayed the warning to Dr Hansen that there would be 'dire consequences' if such statements continued, those officers and Dr Hansen said in interviews," the Times said. In discussions with the daily paper, Hansen said "it would be irresponsible not to speak out, particularly because NASA's mission statement includes the phrase 'to understand and protect our home planet'". It added that he was "incensed that the directives had come through telephone conversations and not through formal channels, leaving no significant trails of documents". The Times quoted Hansen's supervisor, Franco Einaudi, as saying there had been no official "order or pressure to say shut Jim up". "That doesn't mean I like this kind of pressure being applied," he told the paper.


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