Dimming the sun to fight climate change? U.S. researchers are looking into it

U.S. researchers considering dimming the sun to slow climate change The National Academies of Sciences is recommending $100-200 million in funding to better understand the idea.

TORONTO — It sounds not only like an idea straight out of science fiction, but a bad idea straight out of science fiction: shooting particles into the atmosphere to dim the sun as a measure to fight climate change.

However, the idea is one of a few contemplated in a new report by the U.S National Academy of Sciences, Engineering, and Medicine that calls for US$100-US$200 million in funding to examine the feasibility and wisdom of trying to stop some of the sun’s rays from hitting the Earth’s surface.

“One way to respond to climate change might be to try and reflect some amount of incoming solar energy back into space, and the way to do that is … to make some aspect of the planet shinier,” Simon Nicholson, Director of the Global Environmental Politics program at American University, told CTV’s Your Morning on Friday.

The report is not recommending this type of measure at this point. Rather, it says it should be investigated among possible actions to be taken if current efforts to slow carbon emissions aren’t able to slow the planet’s warming.

“Most technologies that we talk about are hopeful, they’re generated by human aspiration. But when it comes to something like this we’re talking about defensive technologies that would only be utilized if the world just can’t get its act together in other ways to deal with climate change,” said Nicholson.

While the economic slowdown from the COVID-19 pandemic reduced greenhouse gas production for much of 2020, emissions rebounded late in the year, and the U.S. National Oceanic and Atmospheric Administration reported last week that carbon dioxide levels in the atmosphere are now higher than at any point in the last 3.6 million years.

The options contemplated focus on the idea that reflecting some portion of the sun’s rays will lead to lower temperatures, much in the way scientists believe that debris sent into the atmosphere by an asteroid strike 66 million years ago lowered Earth temperatures and wiped out the dinosaurs.

One option looked at is called ‘marine cloud brightening’, which would see salt water injected into clouds over the ocean in order to make them brighter and more reflective. Another option, “stratospheric aerosol injection’, would involve putting reflective particles high in the atmosphere in order to reflect incoming solar energy.

While putting the brakes on global warming would be an ideal outcome, it’s not hard to imagine potential problems with the proposals, such as the potential negative effects on crops from a reduction in sunlight. Another issue is that these measures would only be stopgaps for the larger problem of climate change, says Nicholson.

“The challenge here is that if you start a program, then chances are it's going to be continued because all you're doing with something like this is dampening a warming effect,” he said. “This is not actually solving climate change because solving climate change means stopping greenhouse gas pollution going into the atmosphere in the first place.”

For anyone worried about such approaches resulting in a sci-fi nightmare of a permanently darkened Earth, Nicholson says the technologies should be easy to reverse, as salt water would fall out of the cloud layer in a matter of days or weeks, while stratospheric aerosols would likely fall out within two years.

“These things sound like science fiction and they sound like wacky ideas that could be devastating, but so is runaway climate change,” said Nicholson. “The reason that these things are being looked at at all is because if they’re utilized in an effective and cooperative fashion, they might offer a small piece of the response that we need to climate change. But there are downside risks.”