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The Hot Seat

Q&A: James Hansen
The Hot Seat

Having sounded the alert about global warming for three decades, James Hansen has emerged as something of a prophet. In 1988 his congressional testimony helped spur a national debate. Earlier this year, Hansen, director of the NASA Goddard Institute for Space Studies, made more news after revealing that the Bush administration was trying to gag other scientists and him. Audubon recently caught up with Hansen.

Audubon: Greenhouse gases are primarily emitted from power plants and car exhaust pipes, correct?
Hansen: Yes, vehicles are the most rapidly growing source.

Q: How much longer can we continue to heat up the atmosphere before there are significant consequences?
A: At most we have a decade. It’s very simple. There are two different scenarios: business as usual, in which CO2 emissions are continuing to increase by 1.5 or 2 percent per year for decades. CO2 will increase at least 3 to 4 parts per million each year by 2050. That is a guarantee of dramatic climate change, and a guarantee of disasters, including the loss of a substantial fraction of the species on the planet. There’s an alternative scenario, where we flatten out and then get emissions to decline substantially before the middle of the next decade.

Q: You mean “flatten out” CO2 emissions?
A: Yes, instead of increasing 2 percent per year, emissions need to level off, before they can begin to decline. Two percent per year, compounded for 15 years between 2000 and 2015, would put emissions of CO2 in 2015 at 135 percent of the emissions rate in 2000. Then you’re so far off of this alternative scenario, you’ll never get onto it.

Q: What kinds of changes do you mean?
A: The total rate of sea level change is now 3.5 centimeters per decade, which would be 35 centimeters, or a little more than a foot, per century, but it’s doubled from what it was in the 20th century. If it doubles and doubles a few more times, pretty soon you are talking about real substantial sea level change. Ice sheet decay begins slowly, but once you get it started, it will go much more rapidly. So it’s dangerous to let it get to a point where you’re really beginning to see things happening.

Q: Do you think people are now more receptive to information about global warming or to change?
A: I think they are. The question is, is the change going to be sufficiently rapid that there is an impact on policies and the technologies and our emissions of greenhouse gases? We have a very narrow window.

Q: Has the administration eased its grip on you and other scientists?
A: Well, in my case they have, but I don’t believe that scientists at EPA, for example, feel they’re allowed to say what they believe if it doesn’t coincide with official policy. We are government employees. Our salaries are paid by the taxpayers, and yet we’re not allowed to inform the taxpayers? It doesn’t make sense.—Susan Cosier

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