It’s difficult to choose just one word — maybe “carbon zero,” “carbon negative.” If you believe that we have to limit temperature growth to 2 degrees or 1.5 degrees C, then you have to start thinking about essentially no fossil fuel use at all after 15 or 20 years. Even more than that, you have to start thinking about having negative carbon, in which you begin to draw carbon out of the atmosphere in order to avoid a problem.



The depressing thing is if you look at what the country commitments are in the Paris Agreement, even if all the countries did what they said they would do, this problem is going to get worse. So then the question is: What do you do about it?



I’ll continue to try to understand how you can make the transition as rapidly as possible to a zero-carbon future for countries such as the U.S., China, and India, the big players. I’ll also start thinking about some of the negative-carbon possibilities.



We had a paper six months or so ago that looked at harvesting crop waste, combining it with coal, and gasifying it to produce electricity, and then capturing the CO2 and burying it or using it. So that’s a way to think about negative-carbon possibilities.



On the other side, I’m really impressed with the interest — particularly of young people — in the problem. There’s also interest by our alumni groups. Alumni clubs around the country have started coming to the University saying, “We would like to have somebody come and talk about the climate issue.” The interest is really high.



As far as “carbon negative” goes, Al Gore has opened his family farm in Tennessee to people who want to do experiments on how you can capture and retain more carbon in soils. I think the way we can do it is using photosynthetic uptake of carbon and instead of having the carbon simply go back into the atmosphere, find ways to capture it and use it or bury it or sequester it.



Stopping unnecessary deforestation, reforesting areas that are not particularly productive, thinking about more conservative agricultural systems, and managing soils would be good ideas. You want to let the plants take carbon out of the atmosphere and then grab that carbon. But there’s no easy solution.