President Obama’s nominee for a key post at the Department of Energy isn’t optimistic that we’ll be able to stabilize carbon dioxide levels in the atmosphere.

This week President Obama nominated Steven Koonin for the post of Under Secretary for Science, Department of Energy. He’ll head the DOE’s Office of Science, which will receive $1.2 billion under this year’s stimulus bill, in addition to its regular budget. The funding includes hundreds of millions for research related to advanced energy, but a lot of money is also allocated to basic research about the nature of matter, among other things.

Koonin seems uniquely qualified for the job. He’s a former Caltech theoretical physicist, so he’ll understand the basic science pursuits of the agency. He also has practical experience related to energy as the chief scientist at BP. The breadth of his knowledge about energy and climate change is made pretty clear in this speech, available on YouTube.

Koonin used to doubt that humans contributed significantly to climate change, but he changed his mind after some careful study of the subject. Now he thinks we must do something to stop levels of carbon dioxide from rising in the atmosphere. Yet, when I talked to him last fall, he wasn’t confident that the world would be able to do this.

In that interview we talked about two energy challenges. The first was ensuring that the United States has secure supplies of oil, the second was addressing climate change. From that interview:

TR: Are you hopeful that we’re going to be able to meet these challenges?

SK: I’m optimistic about security of supply. I see many sources for liquid hydrocarbons. I see great potential for efficiency improvements in U.S. transportation fleets. I am less optimistic about carbon dioxide emissions reductions. The world should give it its best shot, but there are so many forces aligned against it that I think it’s going to be very difficult for the world to stabilize emissions, let alone stabilize concentrations of carbon dioxide in the atmosphere.

Carbon dioxide lives in the atmosphere for a very long time–a thousand years or so. What that means is that the atmosphere is accumulating emissions, and emissions right now are on an exponential growth path–2 or 3 percent a year. If we manage to make modest reductions in emissions, it will only be in the rate at which the concentration grows, but it won’t stop the growth. So the usual societal response of dealing with a problem partially is not good enough to deal with the CO₂ problem. We really need major changes in the ways we produce and use energy if we’re going to prevent concentrations from rising. I don’t think people understand that.

His assessment seems realistic to me. “Give it your best shot,” however, is hardly inspiring. If he gets the nomination, I predict we’ll hear a lot less of this frank talk as he rallies the troops.