The "Hansen gagging" story has been around a bit... now I find (via Roger on sci.env) this: I am writing in response to several recent news articles indicating that officials at NASA may be trying to "silence" Dr. James Hansen, the director of the Goddard Institute for Space Studies. It ought to go without saying that government scientists must be free to describe their scientific conclusions and the implications of those conclusions to their fellow scientists, policymakers and the general public. Any effort to censor federal scientists biases public discussions of scientific issues, increases distrust of the government and makes it difficult for the government to attract the best scientists. And when it comes to an issue like climate change, a subject of ongoing public debate with immense ramifications, the government ought to be bending over backward to make sure that its scientists are able to discuss their work and what it means. And so on.
[And now checking, I see Prometheus has this already]