Geoengineering to combat climate change

Claire Parkinson: Geoengineering schemes are being proposed with the best of intentions. They’re trying to avoid a climate crisis that many people think will arise if we don’t do something about it.

NASA climate researcher Claire Parkinson is talking about geoengineering, using technology to manipulate climate on a global scale. With climate scientists up to 98% in agreement on human-caused global warming according to recent surveys, some scientists are talking about ideas to deliberately cool a warming planet.

Claire Parkinson: The scheme that’s the most talked about is one whereby aerosols, or small particulate matter, would be poured into the upper atmosphere to reflect sunlight away.

Parkinson compared this geoengineering scheme to what volcanoes do naturally. They shoot particles that reflect sunlight high into the stratosphere. But she said the artificially sprayed particles could bring on new problems.

Claire Parkinson: … consequences that could include damage to the ozone layer, could include increased pollution down at ground level, and could include changes to the Earth’s weather and climate systems that we don’t even know yet how to anticipate.

Parkinson said a safer bet would be to paint the roofs of the world’s buildings white. A study found white roofs could offset the carbon emissions of all 600 million of the world’s cars for 18 to 20 years.

Claire Parkinson: It’s really important to think through these schemes and their potential consequences really carefully before implementing them, recognizing that some could be reasonable, whereas others are way too risky.

Dr. Parkinson said that main thrust of the geoengineering proposals is to reduce the amount of warming. Some fof them are aimed at decreasing how much radiation comes into the system.

Claire Parkinson: Because almost all of the radiation that comes into the Earth’s atmosphere system is coming in from the sun, it’s called solar radiation. The one primary scheme being thought of to reduce the amount of sunlight that comes in to Earth is to use satellite technology and put a shield out in outer space, blocking some of the sunlight from getting in.

However, she said, there are a whole stack of geoengineering schemes to decrease how much radiation goes out.

Claire Parkinson: The scheme there that’s the most talked about is one whereby aerosols, or small particulate matter, would be poured into the upper atmosphere to reflect sunlight away. Since this is the type of thing that happens naturally when a volcano erupts vertically and sends a lot of particulate matter into the upper atmosphere and the Earth ends up cooling a bit because of that. This is sometimes called creating an artificial volcano.

Another possibility, Parkinson said, would be directly letting radiation get down further into the atmosphere and reflecting it lower in the atmosphere.

Claire Parkinson: The main schemes for doing that being proposed would be to brighten the clouds. And this would be to have structures in the oceans that would be sending a mist up into the atmosphere to help brighten the clouds.

Parkinson believes that better way of reflecting at the surface would be instead to put a reflective covering over a building that humans have already built.

Claire Parkinson: This could be done either by adding a reflective covering or simply by painting roofs white, as this would reflect solar radiation to the atmosphere.

While some geoengineering might seem too risky to even be seriously considered, Parkinson said scientists shouldn’t abandon studying it.

Claire Parkinson: Earth’s system is really complicated, and scientists have not yet gotten a full handle on it, even though we’ve made wonderful progress in the last few decades, with all sorts of new tools, like satellite technology, ice core drilling, deep sea core drilling, and computer models that are allowing us to do wonderful things in terms of modeling aspects of the climate system. None of these tools is perfected to the point where we really can be sure about what’s going to happen in the future. We just don’t know enough yet. As time goes on, I could certainly see that more geoengineering schemes could come into play that would be logical to do. But in general, I would say we have to be really, really careful, in terms of thinking through the possible consequences of these schemes.

Our thanks today to NASA and its Science Mission Directorate.

September 13, 2010

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