Last Friday, at 3:40 p.m., the State Department released its “Draft Supplemental Environmental Impact Statement” for the highly contentious Keystone XL pipeline, which Canada hopes to build to move its tar sands oil to refineries in the United States. In effect, the statement said there were no environmental impediments that would prevent President Obama from approving the pipeline.

Two hours and 20 minutes later, I received a blast e-mail containing a statement by James Hansen, the head of the Goddard Institute for Space Studies at NASA — i.e., NASA’s chief climate scientist. “Keystone XL, if the public were to allow our well-oiled government to shepherd it into existence, would be the first step down the wrong road, perpetuating our addiction to dirty fossil fuels, moving to ever dirtier ones,” it began. After claiming that the carbon in the tar sands “exceeds that in all oil burned in human history,” Hansen’s statement concluded: “The public must demand that the government begin serving the public’s interest, not the fossil fuel industry’s interest.”

As a private citizen, Hansen, 71, has the same First Amendment rights as everyone else. He can publicly oppose the Keystone XL pipeline if he so chooses, just as he can be as politically active as he wants to be in the anti-Keystone movement, and even be arrested during protests, something he managed to do recently in front of the White House.

But the blast e-mail didn’t come from James Hansen, private citizen. It specifically identified Hansen as the head of the Goddard Institute, and went on to describe him as someone who “has drawn attention to the danger of passing climate tipping points, producing irreversible climate impacts that would yield a different planet from the one on which civilization developed.” All of which made me wonder whether such apocalyptic pronouncements were the sort of statements a government scientist should be making — and whether they were really helping the cause of reversing climate change.