Thread by @hankgreen

Massively under-reported science story because there's so much going on right now but...it turns out that we might have figured out what's causing this very scary spike.

Quick thread, on how WE'VE BEEN ACCIDENTALLY GEOENGINEERING FOR DECADES...but then we stopped:

So, geoengineering (or climate engineering) is when you intentionally do stuff to change the climate of the Earth. When you accidentally do stuff to change the climate of the Earth, that's just called "The last 100 years."

We've been doing a lot of accidental geoengineering.

The big bit is all of the CO2 in the atmosphere, which heats things up a lot. But we also do other stuff, like for example releasing tons of sulfur dioxide into the atmosphere, which we do by burning dirty fuels like coal and fuel oil.

SO2 actually (very temporarily) cools things down by seeding clouds and creating sulfuric acid aerosols. That's not, like, /good/, but by making more clouds (and also decreasing the size of droplets in clouds, and thus increasing their number) more sunlight is reflected to space.

One big source of SO2 is international shipping. Big ships use dirty fuels, dumping a ton of SO2 into the atmosphere, thus seeding clouds. You can actually see them from space...they're called "Ship Tracks."

Now, sulfur pollution is bad...it acidifies the rain which acidifies the ocean (which is already dealing with acidification). It can cause lung problems in humans and animals. So the UN's International Maritime Organization created a new rule to limit sulfur in ship fuels.

They started enforcing this in 2020...and we "lost the cooling effect from a fairly large volcanic eruption each year" according to FSU atmospheric scientist Michael Diamond.

This article in Science from @voooos is really excellent:
science.org/content/articl…

Models show that the extra warming we've been seeing in the North Atlantic (which is a very busy area for shipping) can pretty much be /entirely attributed/ to the extra sunlight hitting the ocean (which has, this year, also been worsened by less dust blowing from the Sahara.)

Now, in one way, this is very bad news. Global warming is actually worse than we thought it was, we've just been shielding ourselves from it with /other pollution/. Similar effects have been seen when we turn off coal fired power plants.

.climate.mit.edu/ask-mit/should…

In another way, it's good news. The new IMO rules are providing a free natural experiment that would otherwise be both extremely expensive and perhaps politically impossible to pull off. Geoengineering is a fraught topic that many people outright oppose.

But the reality is, we've been geoengineering this planet in a terribly reckless and haphazard way for over a hundred years. Getting a look at the exact effect of releasing SO2 for decades and then the effect of /stopping/ might truly be priceless.

Because it doesn't have to be SO2 we launch into the air to seed clouds, we could do it with salt from the water by simply spraying the ocean into the sky. And we could use the existing fleet of shipping vessels to do it. royalsocietypublishing.org/doi/10.1098/rs…

And the biggest perspective shift for me here is...we shouldn't be asking whether we should be doing geoengineering...we already are, we have been for a century. We should be asking...should take a huge step and do it intentionally and thoughtfully...because WE CAN SEE IT WORKS.

I also made my vlogbrothers video about this this week where I go into more detail. You can see it here: