There are serious scientists in the world right now who believe that a last-ditch effort to save the planet from the worst consequences of global warming could include a bold plan to inject massive quantities of sulfur dioxide into the stratosphere where it will partially block out the sun.

If that sounds impossibly risky or downright foolish, you’re in good company. It’s a frightening notion at first blush, and on closer examination it doesn’t look much more appealing.

“If the idea of putting megatons of sulfate aerosols into the stratosphere doesn’t scare you, I think there’s something wrong with you,” says Douglas MacMartin, a research professor with California Institute of Technology who studies the problem of deliberately manipulating Earth’s climate. He spoke Tuesday at a panel discussion hosted by the American Institute of Aeronautics and Astronautics on the subject of the role of aerospace industries in potential geoengineering schemes.

Geoengineering describes two broad types of projects — ones that seek to pull carbon dioxide out of the atmosphere, and ones that seek to limit the amount of solar energy that reaches this planet’s surface. The U.S. government formally acknowledged the potential need to engineer the climate to mitigate global warming for the first time this week, opening the door to federal research funding in this area.

Pulling carbon dioxide from the air is an entirely sensible way to mitigate climate change caused by emissions of carbon dioxide into the air, and those who have looked closely at the problem tend to agree that this will have to be the ultimate long-term solution to global warming. It is also very expensive and very difficult to implement at the scale required to make a noticeable difference, which is why riskier but shorter-term ideas continue to be floated.

Solar radiation management by seeding the stratosphere with sulfates is undeniably risky. But we know that it works — large volcano eruptions perform this feat naturally, and the effect is that Earth gets cooler, at least for a year or two. It’s also likely to be feasible from economic, technological, and logistical standpoints.

“It’s very quick, and it’s probably very cheap,” says MacMartin. “All you have to do is basically fly airplanes up into the stratosphere and dump a pile of crap up there, and you’ll cool the planet.”

That doesn’t make it a good idea.

“If you push in one direction with increasing greenhouse gasses, and then you try to push backwards in a different direction by cooling the planet, you don’t actually recover the same climate you would otherwise have had,” explains MacMartin. So, a region experiencing increased drought from climate change might become even drier through a solar engineering scheme. The local environmental effects are difficult to predict and measure.

And it does nothing to help ocean acidification, which threatens corals and shell-building marine life, and the vast marine ecosystems that rely on them. “That’s yet another reason why this is a horrible idea,” MacMartin says.

Then there’s the much, much bigger problem of deciding how such a program is deployed, who’s in charge, and how claims for compensation will be handled when some parts of the world are inevitably made worse off than they otherwise would have been.

So, why is MacMartin still researching this terrible, horrible, no good, very bad idea that will likely never achieve social or political consensus? The short answer is, that as scary as a world of geoengineering looks, a world of unmitigated climate change could turn out to be a lot scarier.

In all plausibility, the world will descend into deep and widespread climate crisis before a scheme like solar radiation management is tried on a large scale. MacMartin thinks it will get that bad.

“The hope for not needing this is a rather slim hope at this point,” he tells Inverse by email. “I think it is highly unlikely that we will cut emissions fast enough to avoid serious climate damages, and I think it is therefore pretty likely that geoengineering will eventually be used.”

Though, in this light, the prospect of solar radiation management starts to look less terrifying and more like a saving grace. “One can be depressed that it has gotten to this point, but one can also be hopeful for the fact that we may be able to alleviate a lot of human and non-human suffering,” says MacMartin.

Photos via Pixabay