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Wallace Broecker Geochemist, Palisades, New York

How to stop global warming? CO2 "scrubbers," a new book says

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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.

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