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What are you doing? 

We're using balloons to launch reflective clouds into the stratosphere.


Unless we reflect sunlight (albedo enhancement), 10s of millions of people will die and 20%+ of species may go extinct. We're using the most effective way to reflect sunlight that we've found and can afford to deploy (<$50k startup cost). 

Is this legal?

Yes, we've been in contact with multiple US government agencies (FBI, FAA, an NOAA). They are aware of our business and activities.

I would like you to stop doing this.

And we would like an equitable future with breathable air and no wet bulb events for generations to come. Convince us there's a more feasible way to buy us the time to get there and we'll stop. We'll happily debate anyone on this, just confirm an audience of at least 200 people and we'll find the time to try and convince you 😉

How do you know this will work?

We're copying nature, in 1991 Mt. Pinatubo, a stratovolcano cooled the Earth by 0.9F or 0.5C for over a year.

Isn't geoengineering wrong?

Any human-caused release of carbon dioxide is geoengineering: the earth is a bit warmer for every flight you take. We think it's wrong to suddenly draw a line at the stratosphere: we screwed up the atmosphere, and now we have a moral obligation to fix things!

Why not plant trees and switch to solar panels?

We absolutely should do these and every other effective carbon reduction + clean energy measure. However, we also need to immediately cool the world. Even if we magically stopped all carbon emissions right now, we'd still likely hit 2.3C! Given that greenhouse gas emissions increase every year, we need to start cooling the world immediately.

How long do Make Sunsets' clouds stay in the sky?

Depending on the altitude and latitude at which we release them, between six months and three years.

Why has nobody done this yet?

We have. 😉 Others have tried from academia but were canceled due to well-intentioned but misguided activism and patent disputes

Wouldn't it be more effective to put giant mirrors in space / make special high-altitude planes / run a tethered tube to the stratosphere?

Maybe! We have no religion about how we produce the cooling we need and want the most cooling per $ we can safely + quickly achieve. Personally, we lack the $B+ startup costs (and substantial political capital) for these other methods. If you or your government are credibly attempting to build one of these, we'd be happy to collaborate!

How effective are these clouds?

Shorthand is that "a gram offsets a ton:" one gram of sulfur delivered to 20km altitude creates as much radiative forcing as one ton of CO₂ released in the atmosphere does in a year. There's a lot of uncertainty and assumptions here (including a 3x difference among IPCC scientists on global warming per unit CO₂ ). As we perform more releases, we'll learn a lot more about our efficacy. However, uncertainty isn't an excuse for inaction.

How will you measure the impact of your efforts?

We fly instrumentation (GPS, cameras, and other sensors) with our balloons to verify that the payload reached the stratosphere. As we scale up deployments we can use satellites that can detect SO2 from volcanic eruptions to measure the efficacy of our deployments.

How much to stop making the problem worse?

We can create sufficient cooling to offset this year's new warming for ~$30M per year: $7M of sulfur + deployment costs.

How much would it cost to offset all man-made global warming?

Less than $50B per year: ~$12B of sulfur + deployment costs.

Is the situation really this dire?

No: it's likely much worse. We're very unlikely to stop mining proven petroleum reserves, and even the worst-case IPCC projections of 4C by the year 2100 don't include any massive natural releases of greenhouse gases (tundra methane, etc.). We need to act now to cool the world!  

What about ozone? 

Modeling shows a slight but meaningful depletion in ozone. While we'll closely monitor this, it's important to note that worst-case scenarios for ozone depletion amount to 5-10% on average. This is less than half of what CFCs caused and may be at least partially offset by reduced global warming's positive impact on ozone.

How much carbon do you offset?

None: we're only addressing the warming impact of carbon. Efforts to decarbonize are essential, and directly cooling the world is NOT a substitute. We need to do both to maintain a livable world.

Are these actually clouds?

They are not water vapor, so in a technical sense no. In a "cloud of dust" sense, they are;)

Won't plants grow more slowly? 

Preliminary modeling actually shows the opposite: an ~10% net increase.

What is the benefit vs. harm of stratospheric aerosol injection?

100 people benefit from and 1 person is harmed if we deploy enough to cool the Earth by 1C.

Source: https://youtu.be/NZ8TZqfwzdU?t=2246 "Towards Quantitative Comparison of the Risks and Benefits of Solar Geoengineering." by Dr. David Keith.

How can I purchase a cooling credit?

Go here! If you're a company looking to offset your CO₂ equivalent emissions and purchase more than 1,000 Cooling Credits, please email andrew@makesunsets.com with your company email for bulk pricing. 

Who have you done this for?

We've completed 40 deployments for over 220 customers as of December 2023 and neutralized the equivalent of neutralizing the emissions of 1,964 cars for an entire year.

I want to help you / how can I get involved?

We follow Y Combinator's mantra: Make Something People Want. We've made this, and now we need to prove people want it. Introductions to companies that want to purchase cooling credits and/or countries interested in hosting balloon launch sites would both be very helpful.

Why aren't you using hydrogen as a lift gas for your balloons?

We are currently using helium as a lift gas because it's safer than hydrogen in storage. As we increase the frequency and size of our deployments it makes fiscal and sustainability sense to switch to hydrogen.