A Science Adviser Unmuzzled

Earlier this year, James Hansen, NASA's chief climate scientist, made headlines when he accused the administration of muzzling him when he tried to speak out about global warming. Hansen, director of the space agency's Goddard Institute for Space Studies, was one of the earliest researchers to sound the climate change alarm. He alleges that White House appointees in NASA limited his access to the press and ordered him to remove web postingss that contradicted the President's positions. The White House took a PR bruising when the charges went public and Hansen's profile has since been higher than ever. He recently spoke to TIME about both the science and the politics of the global warming crisis.

TIME: Are we correct in thinking that a climatological collapse has begun, and if so, when might we reach the stage at which it would be out of our power to fix things?

Hansen: We are getting close to a tipping point, despite the fact that most people barely notice the warming yet. We have witnessed 1°F warming in the past 30 years. There is 1°F more in the pipeline due to gases already in the air. Still another degree is certain because of energy infrastructure already in place, such as power plants and vehicles on the road. Three degrees will take us to a level at or just above the warmest in the past million years. The changes at that level are substantial but something we can probably adapt to. In order to limit change to that level we need to get on a track that I call the alternative scenario, which requires that we begin to slow emissions this decade and substantially reduce them before mid- century. If we stay on a business-as-usual path for another decade, the alternative scenario becomes impractical if not impossible.

TIME: What is that alternative?

Hansen: Business-as-usual will yield warming of 6 to 9°F by the end of the century and that will have two major impacts. First, sea level will rise. The last time it was 5°F warmer than now sea level was at least 80 feet higher. It may take a few centuries for most of that rise to occur, but once started, the ice sheets would continue to disintegrate out of our control, so every several decades we would need to rebuild above a higher shoreline. Those costs would dwarf any costs associated with learning to use energy more sensibly. Second, we'll lose animals and plants. We would push the polar species and alpine species off the planet. On the other hand, the climate change and CO2 in the air will be good for aggressive, weedy plants such as poison ivy.

TIME: The idea of tipping points and feedback loops catches a lot of people by surprise. Were the scientists blind-sided too?

Hansen: Not really, but not enough thought was given to the potential for large sea level changes, probably because of the assumption that it takes the ice sheets millennia to respond. I have argued the importance of sea level and I think that realization is catching on. I do think, on the other hand, that many scientists are spending too much time trying to figure out the effects of possible changes in the ocean's circulation. Europe, and the U.S., will not freeze over or get colder if the Atlantic circulation slows down. Global warming overwhelms the modest effects of reduced heat transport.

TIME: If atmospheric carbon is currently at 380 parts per million, how long do you think it take before aggressive action would begin to bring it down?

Hansen: We have to first level out emissions, then get them to start to decline. By the end of the century we could reduce emissions by perhaps 70% so that atmospheric CO2 would stabilize.

TIME: Have you noticed a sea change in public perception and willingness to do something about the problem?

Hansen: Not a sea change, but they are beginning to wake up, and this coincides with the science becoming a lot clearer in the past five or six years.

TIME: What about political perception and political willingness?

Hansen: Incredibly, there are still staunch deniers who would prefer to listen to a science fiction writer [Michael Crichton, author of "State of Fear," which challenges global warming science] rather than a real scientist. It is perhaps not a coincidence that the strongest deniers among the politicians have connections to the fossil fuel industry.

TIME: Do you have any hope that the White House will act?

Hansen: We can't give up, no matter what the odds look like. Another three years of business as usual will make it much harder to avoid large changes.

TIME: Aren't regional and local action like the mayors' and governors' initiatives mostly window dressing? Can they really make a dent in carbon output if Washington doesn't do something?

Hansen: They are useful practice, but, yes, it is absolutely essential that the U.S. take a real leadership role. Until that happens, it is basically business as usual.

TIME: If you could write the next Kyoto treaty, what provisions would you include?

Hansen: I should note that I don't make policy and my opinions are personal. We do need a strong disincentive for exploitation of the "worse than coal" energy sources such as tar sands and shale oil.

TIME: You started as something of an environmental scold and lately you've become more of an environmental hero. Feel vindicated?

Hansen: I'm not sure exactly what you mean, but there is no time for feeling good until the U.S. begins to take the leadership role that it is capable of.