What if we just blocked out the sun?

Mr. Burns would be pleased, but what about us?

sun breaking through clouds

Extreme heat is on the rise, and when combined with high humidity, it could threaten the lives of up to three-quarters of the world population by 2100. One potential salve for all this sunlight: solar geoengineering, a method that sends wee particles into the atmosphere to reflect those rays. But this technique has risks, and recently atmospheric scientists have been imploring regulators to slow the roll and consider the caveats of blocking the sun. Here’s what you need to know about the futuristic-sounding concept.

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What is solar geoengineering?

Solar geoengineering—technically speaking, “solar radiation modification”—releases aerosols such as sulfur dioxide into the stratosphere, the second layer of the Earth’s atmosphere. This could decrease temperatures quickly by bouncing solar rays away from the surface (about $10 billion a year could lower temps about 1 degree Celsius, according to CNBC). The method imitates the natural cooling effects that atmospheric scientists observe around volcanic gas. According to the Carnegie Climate Governance Initiative, it could also have added benefits like reducing extremes in precipitation and slowing Arctic sea ice melt.

Are there downsides?

Atmospheric scientists warn that solar radiation modification is a temporary solution at best. It doesn’t mitigate all climate change harms—and starting, then stopping, the process could even cause temperatures to rise rapidly. It comes with a lot of other risks, too, like regional changes in precipitation, thinning of the ozone layer, excessive cooling, and increased acid rain. It could also threaten global security: Just imagine if one country uses it and causes negative impacts to a neighbor.

But there’s an even bigger issue. Hundreds of scholars from across the world have signed an open letter against the practice. They argue that it distracts from what’s most important: decreasing emissions and removing carbon dioxide from the atmosphere. 

Is solar geoengineering being used anywhere?

Currently, no country or region is using the technique on a large scale, says Tyler Felgenhauer, a research scientist with the Modeling Environmental Risks and Decisions Group at Duke University. There aren’t any talks of it beyond research experiments either. On a small scale, at least one company is trying it on their own, sending balloons that release “reflective clouds” of sulfur dioxide in the sky. (They even sell $10 “cooling credits” to the public.) 

Considering the potential drawbacks, a small group of experts petitioned the National Oceanic and Atmospheric Administration in March to strengthen its regulatory grip on the technology. Currently, all a U.S. company or citizen needs to be able to release aerosols into the atmosphere is to submit a single-page form to the NOAA 10 days before, E&E News reports. The petitioners argue that the existing rule was written in the 1970s about weather modification and that NOAA should consider clarifying and expanding reporting regulations for private solar radiation modification efforts. 

Is there international oversight for solar geoengineering?

Very little. Although some international treaties and U.N. resolutions bring up solar radiation modification, no international governance is dedicated to its study or regulation. Ideally, there should be a group like the Intergovernmental Panel on Climate Change (the IPCC for short) for assessing the research on it, Felgenhauer says. An international team is also needed to decide how solar geoengineering could be deployed in the future—and prevent unrest if some areas suffer negative effects.