A shipping container ship flying in the stratosphere emitting sulfur dioxide to cool Earth.

Move Smoke to Cool Earth

A successful "gee whiz" story of late has been analysis of the warming impact caused by tightened fuel regulations for container ships. I'm thankful for the springboard to sulfur dioxide these stories provide, and it made me wonder:

  • What's the warming impact of these tighter regulations?
  • How can we offset this warming?
  • What would happen if we move *all* this saved sulfur dioxide to the stratosphere instead?

How much sulfur?

What's the quantity of sulfur we're talking about, and what does it do? Bunker fuel is nasty stuff, minimally-processed oil burnt in giant quantities to power some of the largest moving objects humans have ever made. 2020 rules tightened regulations around how much sulfur dioxide this fuel burning can create, and this has been a huge win: 8.5 million tons less sulfur dioxide coming out of ship's smokestacks. This means less acid rain and healthier air for people to breathe, but it has a "gee whiz" downside: sulfur dioxide reflects some sunlight, and less sulfur dioxide means less reflectivity. Less reflectivity means more warming: this dirtier smoke was cooling Earth! NASA saw the result by comparing satellite photos:

How much warmer?

Scientists now know roughly how cleaner ship smoke has changed Earth's reflectivity: 0.1 W/m2. From previous work, we know that 1 W/m2 of change in reflectivity translates, after equilibration, to about 0.7C of global average temperature change. So, cleaner ship fuel will warm Earth by ~0.07C.

How can we fix this?

It won't surprise any frequent readers to hear that there's a way we can make sulfur dioxide emissions more effective. Per ton, sulfur dioxide released into the stratosphere creates ~25 times as much cooling as that released at ground level! If the aerosol emissions from ships were placed in the stratosphere instead of eliminated, this would have been more than enough sulfur to offset all global warming that has occurred to date. To offset the warming created by cleaner ship fuel, we can put 0.34 million tons of sulfur dioxide into the stratosphere. Yes: the "into the stratosphere" part is not free or trivial. But, we're talking about a quantity doable with current balloons or planes. With the payload on NASA's biggest balloons, 100,000 flights gives us room for a bunch of failed launches and heavy telemetry on every flight. This is less than half the number of flights that took off from JFK Airport last year.

Take Me Higher!

What if we put all this sulfur dioxide we saved from cleaner ship fuel into the stratosphere, and continue to do this every year? We don't know exactly, but it's likely this would offset *all* warming from human's greenhouse gas emissions. This would translate to millions of lives saved, thousands of extinctions prevented, and trillions of dollars saved. Every year. And a more livable world. And we could do it with 2.4 million launches of existing NASA balloons per year. This is only 7 times more flights than ATL Airport handles. And, it will cost ~$10 billion dollars per year. Most importantly, we maintain a livable world and buy ourselves time to decarbonize.

Start With A DFW

To be clear, we don't know exactly what will happen if we suddenly put 8.5 million tons of sulfur dioxide into the stratosphere every year. But, we do know what will happen if we put a Dallas/Fort Worth International Airport worth of Cooling Credits up: with 328,000 NASA balloon flights per year, we'd cool Earth by over 0.25C.

What are we waiting for?

We're launching monthly and ready + raring to do more! If you have the financial means to do so, you can subscribe to Cooling Credits here. More importantly, push the governments and companies you interact with to do the same. We can and should move smoke higher to Cool Earth!

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