Reflecting sunlight would cool the Earth, but Minnesota researchers find far-reaching consequences

In the year or two after a major volcano erupts, shooting untold tons of sulfate and material into the air, the Earth's temperature typically cools by a few degrees.

As greenhouse gas emissions continue to climb, scientists have been studying the volcanic effect to see if it could be replicated as a drastic, long-shot way to reverse some of the effects of climate change. Clouds of tiny particles would be released high up into the atmosphere to reflect sunlight and solar radiation back into space before it warms the planet.

The case for someday needing the method has grown to the point that ecologists are calling for more studies on not just the mechanics of how it would be done, but the ramifications, side effects and costs. Much more work is needed to know if the damage caused by releasing more particles into the air would outweigh the benefits of cooling the Earth, said Jessica Hellmann, an ecologist with the University of Minnesota.

"If you think of it like chemotherapy, you would only consider taking chemotherapy if the alternative is something as scary as cancer," she said. "This is an intervention that nobody would want to do, but someday we may be forced to do."

Hellmann helped write a study published this month in the Proceedings of National Academy of Sciences that broke down some of the risks and consequences of reflecting sunlight away from the Earth. Research into the proposal is so new that the study offers one of the first looks into its effect on human and animal life.

Weather patterns would almost certainly change in unpredictable ways, increasing rainfall in some areas and reducing it in others, the study found. The changing weather and reduced radiation would force some species of plants and animals to migrate or go extinct. Crops would be less productive with reduced sunlight. The growth of trees and plants in forests and ecosystems around the world could be stunted as well.

One thing that is clear is that reflecting sunlight would work in lowering temperatures, Hellmann said.

"We've seen it with volcanoes where a lightweight material, usually with a sulfur component, stays aloft for a long period of time," she said. "But if you can imagine humanity essentially setting off simulated volcanoes every few years, what would that mean ecologically?"

It isn't known yet if the reflective particles could be released in a way that targets certain areas where cooling is most needed. If solar radiation could, for example, be bounced away from some of California's forests it could reduce the severity and frequency of wildfires.

Reflecting light away from Minnesota in the winter could theoretically keep ice on lakes longer, reducing algae blooms and helping cold-water-loving fish such as cisco, trout and walleye. But days are so short during Minnesota winters, it's unclear how effective the method would be.

Reducing heat alone won't lower the amount of carbon or greenhouse gases in the atmosphere. Those gases would still end up in the ocean and in freshwater lakes, raising acidity and killing off coral reefs and much sea life.

The potential consequences are so poorly understood and risky that the best solution, by far, would be to simply reduce the amount of greenhouse gases released into the atmosphere, Hellmann said.

"A doctor might say that it's always a good idea to quit smoking, and that's true for climate change," she said. "Every ton of carbon dioxide that doesn't go into the atmosphere won't warm the planet. The point is, yes, let's make it so these strategies aren't necessary, but we have an obligation to think through what the consequences of these strategies will be if we need them."

Greg Stanley • 612-673-4882