Solar Geoengineering is like pulling the goalie


by Ralph C. Martin

During the financial crisis of 2008, I first heard about the possibility of solar geoengineering i.e. planes spraying sulphate particles high in the atmosphere to reflect sunlight back to space. I had invited Gwynne Dyer, an author and historian, to speak in Truro, NS. He stunned many of us by saying that politicians would delay addressing climate change until solar geoengineering was the only option left.

When I contemplate too long about what we might have done from 2008 until now to reduce greenhouse gas emissions (GHGs), contrasted with the paucity of political action in that time, I have to slap my forehead and utter “Ugh.” It’s like a highly rated hockey team frittering away their final series until they are down a goal in the last minute, of the last period, in the last game, and then pulling their goalie, to gain more offence. The desperate effort could backfire and seal their demise.

Carbon dioxide (CO2) levels were 385 parts per million (ppm) in 2008, but are now beyond 415 ppm, too far north of the 350 ppm needed to restore climate stability. We’re nearing the end of the third period.

Policies are urgently needed to reduce GHGs by at least 7% each year from now to 2030 and beyond. In 2020, it appeared that a 7% reduction could be attributed to COVID-19. Now that we know it is possible, we need political will to decrease GHGs another 7% in 2021 and another 7% in 2022 and so on.

Regardless of lower emissions in 2020, it was the hottest year on record, along with 2016 ( Think of GHGs going into an almost full bathtub. If the inflow (GHG emissions) declines by 7%, there are still too many GHGs in the bathtub that is too slowly draining (e.g. sequestration of carbon by trees and forage crops). That is why more incentives are needed for farmers and foresters to sequester more carbon, and for industries and citizens to emit fewer GHGs every year.

Our habit of pouring CO2 into the atmosphere means that oceans will absorb some of that CO2, and keep acidifying. Reflecting light back into space from sulfur dioxide would still allow CO2 build-up and thus put marine life under stress. Sulfur dioxide also might delay ozone regeneration in the stratosphere.

“Blocking the sun could come with a host of other issues from negative impacts on crop productivity and shifts in rainfall” ( Furthermore, having started solar geoengineering, we may be committed, because to stop would be to allow too much solar radiation through, too abruptly.

“Sulphate particles would not stay aloft for more than a couple of years …The Asian monsoon, on which 2 billion people depend for their food crops, might shut down” ( How will soils, crops, forests and water bodies respond to continuously descending sulphate?

Will this research tempt politicians to dither about reducing GHGs even more than they already are? Who should decide, and on what authority, if and when to start solar geoengineering, with given specifications?

Recent research is suggesting solar geoengineering may not have substantial negative consequences ( The researchers suggest lower levels of solar geoengineering than originally proposed, might work.

We only have one planet. Models, while helpful, are inexact. Do we want to risk this one planet, with a potentially dangerous ongoing global intervention, based on models? A well-known philosopher, Yogi Berra, said “In theory there is no difference between theory and practice. In practice there is.” In practice, our planet experiences increasing intensities of hurricanes, floods, droughts and fires. We also still have the practical option to reduce GHGs every year. Let’s get on with it, before the end of the third period.

Ralph C. Martin, Ph.D., Professor (retired), University of Guelph. Author of Food Security: From Excess to Enough at


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