Animated by the “move fast and break things” credo that permeates Silicon Valley, the founders of Make Sunsets have no such concerns. They are selling “cooling credits” to customers who want to offset their personal carbon emissions. And a few times each month, after selling enough credits, they head for the hills and release balloons full of sulfur dioxide into the California sky.

“This is the one tool realistically that can cool Earth in our lifetime,” said Mr. Iseman. “Every day we’re not doing this leads to needless harm.”

Sikina Jinnah, a professor of environmental studies at the University of California Santa Cruz who has studied geoengineering, is also concerned about harm. “They are a couple of tech bros who have no expertise in doing what they’re claiming to do,” she said. “They’re not scientists and they’re making claims about cooling credits that nobody has validated.”

Yeah....Gotta admit I didn't have a lot of confidence in the idea when I first started reading the article. Then I read this part and my confidence went from low to zero.

One problem I have with this idea is that the cooling profile from releasing sulphates into the atmosphere looks very different from the greenhouse gas warming profile. For example, the latter has a more pronounced effect at higher latitudes, since GHG are insulators. The arctic is getting hit harder than the tropics. The former, I would expect, would affect the places in the world that get the most sun, since it is effectively a solar filter. So, the lower latitudes, in other words.

If we have a baseline scenario A of what would have happened without the GHGs and B with what is currently happening, this would make for a scenario C that is neither of the others. I would submit that C would likely be as far from A as B is. Yes, you might get global warming under control in an accountant-looking-at-only-the-bottom-line sort of way, but this would still represent a massive climate change into uncharted territory. Would scenario C still be preferable to B is the question I guess?

The part where he asks 'what am I missing here?' falls on silent ears...

Sulfur dioxide added to the atmosphere through human action does contribute to reducing global temperatures. There's a Nature article about it. From their abstract:

In 2020, fuel regulations abruptly reduced the emission of sulfur dioxide from international shipping by about 80% and created an inadvertent geoengineering termination shock with global impact.

Ships had been emitting a lot of SO2 and the effect of abruptly stopping that is apparently quite large:

a doubling (or more) of the warming rate in the 2020 s compared with the rate since 1980

In other words, the laws against SO2 emission by ships are making global warming twice as bad. It's ironic that environmentalists are contributing as much to global warming as everyone else put together.

The guys running this company sound like loose cannons, but it may take a loose cannon to overcome the bias that institutions have towards doing nothing rather than taking an action that involves risks. It's true that adding SO2 to the atmosphere may have serious unintended consequences, although the huge amount that ships had been adding until recently wasn't catastrophic. However, doing nothing as the planet keeps warming will definitely have serious unintended consequences! It's the trolley problem: these guys are pulling the lever and their critics are saying "They're going to kill one person!" but if the critics had their way, five people would die.

I haven't finished it yet, but Neal Stephenson's newest book Termination Shock deals with this exact concept, from what i can tell.