Department of Climate and Space Sciences and Engineering in the College of Engineering at the University of Michigan


Is it time to get serious about geoengineering?

Posted: March 7, 2016

Is it time to get serious about geoengineering?

Professor Joyce Penner recently spoke with Gabe Cherry of Michigan Engineering about geoengineering. Below is an excerpt from the article:

Penner has spent decades studying atmospheric aerosols – both the natural variety that makes up clouds and the artificial aerosols that sulfate injection would spray into the sky.

Penner helped write the 2015 National Academy of Sciences report on geoengineering technologies. She believes that the behavior of atmospheric aerosols is the most crucial unknown in the long list of questions about albedo modification. That’s because aerosol injections are influenced by a huge number of variables: the quantity of aerosol injected, the location of the injection, the size of the individual aerosol particles, cloud conditions at the time of injection and many more.

To get a handle on the specifics of albedo modification, we need to understand these factors. Right now, we don’t. In fact, Penner says, most of the computer model simulations conducted so far don’t factor in the behavior of aerosols at all. They simply “turn down the sun,” measuring the consequences of a theoretical reduction in sunlight rather than the effects of an actual aerosol.

“Every model I know makes some assumptions, but it’s hard to verify that your model is correct because we don’t have adequate observations,” Penner said. “And the aerosol problem is so regionally diverse that you can’t trust an answer in one place as being good for the whole world.”

Penner believes that small-scale field experiments could help us get the knowledge we need to move the science forward. They would be far too small to affect the climate or alter weather patterns, but they’d give researchers a better handle on the complex workings of aerosols in the atmosphere.

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