Philip Rasch sees geoengineering to prevent global warming as last resort

Philip Rasch: Scientists view it as a last resort. They don’t really want to do geoengineering.

Philip Rasch is an atmospheric scientist at the Pacific Northwest National Laboratory. He’s talking about geoengineering. That’s the process by which humans deliberately alter the atmosphere, with an intent to cool the atmosphere – and counter global warming. Scientists believe global warming, caused by a buildup of greenhouse gases, is happening today.

Philip Rasch: The particular kind of geoengineering that I work on is called solar radiation management. If we make the planet just a slight bit more reflective, that might act to cool the planet slightly.

That can be done, said Rasch, by using aircraft to continually spray tons of reflective particles of sulfur dioxide high into the stratosphere. These particles could help cool the Earth, but also potentially disrupt rainfall patterns and other natural systems, he said.

Philip Rasch: The best option by far is to reduce the emissions of greenhouse gases, primarily CO2 and methane. But it requires a really substantial transformation of the way we produce energy in society. And we’re not seeing any evidence that mankind is moving to address that issue.

Dr. Rasch and other scientists are now using computer models to simulate what might happen if humans do need to geoengineer the planet.

Dr. Rasch described in more detail the solar radiation management project he’s working on.

Philip Rasch: The idea is with solar radiation management, or sunlight management, is we’d make the planet a little bit more reflective to sunlight, so we’d cut down slightly n the amount of energy entering the Earth’s system also. If we trap a little bit more energy by greenhouse gases, and we reflect a little bit more energy by geoengineering, we think we might be able to balance those two effects and keep the temperature around the same as it is today.

Dr. Rasch said there are possible consequences of geoengineering.

Philip Rasch: There are a number of possible negative consequences that we know about. We can call them, in the words of Donald Rumsfeld, the ‘known unknowns.’ And then there are the ‘unknown unknowns.’ There are things that we haven’t even envisioned that could conceivably go wrong as well. So as far as the ‘known unknowns,’ for example, by putting aerosols into the stratosphere, we would change the amount of direct sunlight that would reach the surface of the Earth. After Pinatubo, for example, the sky looked whiter during the day time and redder in sunrise and sunset. And that’s a result of the additional scattering from those particles introduce into the sunlight. So plants use diffuse or scattered sunlight differently than they use direct sunlight. And the scattered sunlight tends to reach deeper into the plant canopy. And it increases the productivity of plants.

He said that less light reaching Earth Would also makes it more difficult to produce solar energy:

Philip Rasch: Via the techniques that we currently use with solar concentrators. It’s easier to concentrate sunlight to make electricity if the sunlight is reaching the Earth’s surface directly, rather than in many different directions, as it would be with scattered sunlight.

May 3, 2010

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