Wallace Broecker Geochemist, Palisades, New York

Wallace Broecker, of Columbia University's Lamont-Doherty Earth Observatory, first warned in the 1970s that the earth would warm because of a buildup of carbon dioxide and other gases released by burning fossil fuels. In his new book, Fixing Climate (co-authored by Robert Kunzig), Broecker, 76, argues that we must not only reduce emissions of carbon dioxide (CO₂) but also remove it from the atmosphere on a massive scale to avert environmental ruin. He is an unpaid adviser to Global Research Technologies, a Tucson firm developing devices to capture CO₂ from the air.

By the 1970s, you already believed that CO₂ from emissions was causing global warming.
Looking at the earth's past climate told me that the earth is very sensitive to changes. It concerned me that as we warmed the planet we were heading into unknown territory. I've convinced myself that it is going to be absolutely necessary to capture and bury CO₂. The best way to do that is to take it directly out of the atmosphere. 

How do you "fix" climate?
We need something that can be manufactured, like air conditioners or cars, by the millions. Each day, a unit would take about a ton of CO₂ out of the atmosphere, liquefy it and send it out through pipes to wherever it's going to be stored. The developers are now envisioning a device about 6 to 10 feet in diameter, 50 feet high. It would be like a little silo, in that shape so the wind could blow through it from any direction.

CO₂ emissions are going up faster than the highest scenarios. Developing nations are going gangbusters using fossil fuels, so they are eclipsing any savings that the rich nations are making. At some point we are going to have to get tough about it. There is going to be a demand to bring the CO₂ level back down again because of the environmental damage it's doing. The only way to do that would be with this sort of device.

How many devices would be needed?
Each of us in America is responsible for generating about 20 tons of CO₂ a year. So I suppose roughly 17 million scrubbers would take care of the United States. Worldwide, we'd need a lot more. On a long time scale the rich nations can do more than just stop or neutralize their own emissions. They can also neutralize some of what was done in the past.

The scrubbers don't have to be near the source of pollution?
No. They can be put anywhere. The units would operate best at low humidity and would be best deployed in deserts.

What happens to all the CO₂ the scrubbers take out of the air?
There are many places to store it. The most obvious is the saline aquifers that are under every continent. Ultimately, I think we'll want to put CO₂ into the deep sea. We at Columbia are exploring with Icelanders the possibility of injecting CO₂ dissolved in water into basaltic terrains that make up the earth's mantle, to combine the CO₂ with magnesium and convert it into a mineral. One has to figure out a clever way to do this without using a lot of energy.

Of course, this whole thing has been a race against time. We have done relatively little since 1975, when I first became really concerned about climate change. People say Kyoto was a great accomplishment. It trimmed production of CO₂ a bit, but it's just one percent of the solution. We've got a huge distance to go.

Is this safe?
We're going to have to prove that. People aren't going to want CO₂ underneath their houses unless they can be assured that it's not going to come back in any violent way. I think it would be easier to convince people that putting it in the deep sea is safe.

We have to do something. Otherwise we're going to have a very hot planet and the environmental damage is going to be huge. Any solution is going to have its own environmental consequences. We have to make sure those are very small compared to the consequences of doing nothing.

What about alternative energy sources?
I don't think anybody believes that alternatives will supply the energy we'll need. The long-term solution is solar electricity. But it is far too expensive—there have to be breakthroughs. If they were to occur in the next 10 or 20 years, great, we could put the whole CO₂-capture idea on the shelf. But we have to develop that technology, because it looks right now like solar energy is not going to become affordable in that time scale. We are going to need some way to bail ourselves out.

We have enough coal to run the planet for several hundred years. We could make gasoline out of coal for the equivalent of $50 a barrel. People are not going to use solar energy if it costs 10 times more than energy derived from coal. We are not putting enough resources into developing the technology to capture and store carbon. Everybody is worried about carbon footprints as if that is a solution. It's not. It is important, I'm not putting that down, but conservation in itself can't do it. The world has to run on energy.

How would we pay for the carbon scrubbers?
Whenever carbon is taken out of the ground in whatever form, some sort of tax would be paid. Ultimately there would be a smooth system. Carbon is taken out, a price is paid and that money goes to companies that are burying it. Of course, the transition from nothing into this huge enterprise is very complicated. An enormous amount of work has to be done.

With all of the greenhouse gases being produced, could capturing and storing really put a dent in climate change?
It would have to. Otherwise why do it? Most of us think that by the year 2070 we need to have a carbon-neutral planet. We can no longer increase the CO₂ content of the atmosphere. But poor people on the planet are going to want to have a decent standard of living. To have a decent standard of living requires energy. Just take China. Their energy use is going to go way up. China has coal, so they burn coal. The temptation is going to be to go to a coal economy. Every time we create some CO₂ we have to take the equivalent amount out and bury it. To capture and bury all the CO₂ we're going to be producing is something like $600 billion a year for the world.

Do you think the world is ready for millions of CO₂ scrubbers?
No, I don't think so. Not yet. People are really concerned about CO₂ that's true. But I don't think most people realize how tough a problem it is and what's really involved. The awareness doesn't extend to the tough decisions that are going to have to be made by the world if we are going to ever rein this thing in.

Are you optimistic?
I'm an optimist, but I wish I was a little bit younger and could see how this thing really plays out over the next 50 or 60 years. It will be the major issue in the world for a long, long time.

As the world seriously warms, the realization that we have to do something is going to become ever more intense. Clearly something is happening.