Ralph J. Cicerone, one of the nation's leading experts on climate change, is an atmospheric chemist who has made major contributions to understanding ozone depletion and the behavior of greenhouse gases. Now president of the National Academy of Sciences, Cicerone is planning a new yearlong study, requested last year by Congress, to advise the nation's policy makers on climate change. The study will offer guidance on how to cut greenhouse-gas emissions, what climate changes are inevitable, and what future research is required to understand these changes more clearly. Cicerone recently spoke with Technology Review's chief correspondent, David Talbot.

Technology Review: What research still needs to be done to understand climate change?

Ralph Cicerone: One of the things I would put money into is a climate observing system. Today, we have a patchwork of ways we are observing climate and climate change--a historical legacy of low-tech methods of measuring temperature and precipitation. We've never even strategized carefully about how to create a longer-term climate observing system to tell us what's happening and give us the basis of prediction that we need--both for climate research and to help us know how to adapt to a different climate.

TR: In what areas, for example?

RC: If you think about one of the biggest unknowns in climate change--the rate of ice loss and sea-level rise--we have to know more about ocean-water temperatures, not just at the surface, but at greater depths. To my knowledge, no one is even taking the data at the right places. I don't think it could be done with remote sensing. It could be done with buoy systems and larger oceanographic operations. And this could take a lot of money, but without these data, we're going to have big holes in our ability.

TR: It's clear enough that there's a vast gulf between human-caused greenhouse-gas emissions and the ability of the planet to absorb them.

RC: The fossil-fuel input to the atmosphere, in terms of carbon, is eight billion tons a year, and the net uptake capacity of the whole earth is about three billion tons a year. And the terrestrial biosphere is losing carbon, to the tune of 1.5 billion or 2 billion tons per year, mostly from deforestation. So the annual imbalance is six or seven billion tons.

TR: Given the unique scale and intensity of coal emissions, isn't it already clear that we need to stop burning coal unless we sequester the CO₂?

RC: That's easy to say but a lot harder to do. There is a great deal that can be done with efficiency of coal plants too. Today, they are 35 to 40 percent efficient. Just going to cogeneration alone can capture 60 percent of total energy. The climate issue is the new force that has to be taken into account in these decisions, and it has never been taken into account before.

TR: But what if you did take climate into account with regard to coal?

RC: What we know says that we've got to cut back on emissions from coal--severely. I'm not willing to say we have to stop all coal plants because I don't know how it can be done, because our dependence is so great. But I am willing to say that from everything we know now, those emissions are going to have to be cut back severely.

TR: Is large-scale carbon sequestration feasible?

RC: I don't think it's been shown to be feasible yet. There are some major research questions, some of them geological, some of them chemical. On the chemical side, the question is whether CO₂ has to be captured as a gas or can be processed on-site into a solid. There are some interesting new ideas on how to grab the CO₂ using mineral chemical processes to make a solid, rather than just capturing the gas, and there could be a mixture of approaches. And on the geological side, the safety of long-term storage and the efficacy of it has yet to be demonstrated on the colossal amounts we are looking at.