No one is coming to save us. Time to cowboy up!

Hi there,

Today's Keep Cool edition was written by Andrew Song, the co-founder of Make Sunsets. Increasingly, I will occasionally turn these pages to others to collaborate with me or publish their own ‘op-eds’ (which I think is a worn-out term; “op-eds” can be highly analytical and rigorous). I only offered light edits and some resources + data additions.

Five more editors notes (feel free to skip straight to the Deep Dive as desired):

• There are dead players and live players (credit to Samo Burja for conceiving of this heuristic) in any field. That’s especially relevant right now, as we’re in the midst of radical change across industries, social norms, planetary climate systems, geopolitics, and whatever else may come to mind for you.

• Per the coiner of the concept, Samo: “A live player is a person or well-coordinated group of people that is able to do things they have not done before. A dead player is a person or group of people that is working off a script, incapable of doing new things.” In my words? Dead players are stuck in old paradigms. They’re incapable (at least, absent evolution) of adapting to new paradigms, of shifting entrenched, engrained behaviors and how they see and operate in the world. Side note on a past political example offered at the end of this newsletter.**

• Live players, meanwhile, are, at the minimum, willing to test and tinker, often well outside the norms of past paradigms, in service of finding new models, practices, ideas, and strategies that can actually shake things up (ideally positively vs., say, in service of accelerating extraction and the consolidation of power and wealth).

• Re: this newsletter takeover, I (Nick) am not some Make Sunsets groupie. If nothing else, I think a) geoengineering is firmly in the “climate” zeitgeist now and isn’t going anywhere (I’ll give myself some credit here, having discussed it since 2023), and b) Make Sunsets is a “live player.” The field of ‘climate’ work is—from my vantage point—littered with dead players (including myself to an extent!). I’m talking about organizations, companies, corporate and national ‘commitments,’ communication frameworks, and lifelong institutionalists and rule followers who try and have tried mighty hard but haven’t bent the overarching curve of warming, global emissions, or global decarbonization for 30+ years now (see chart below for visual evidence to that point). Sorry to say it! & I’m guilty, too.

• Hence, we should pay attention to the live players, especially as live players in other fields (*cough cough,* the new U.S. Federal admin, go “shock and awe” mode while the dead players (geriatric politicians, crumbling legacy media, etc…) throw up their hands and say, “This is unprecedented! You can’t do that!”) As bad as some, if not most, of what’s happening politically in the U.S. is, in my opinion, it illustrates the power of what live players can accomplish in short order. So… the invitation is to all work on becoming ‘live players’ in service of good ends.

Final note: Make Sunsets is paying me nothing to publish this. I’m not here to push their approach or their project. I’m here to push the conversation. Lots of folks don't like their approach. That's cool, welcome in fact! That's what we need more of, at minimum in addition to the ‘kumbaya’ renewables-only boosting, doom & gloom, policy-focused, and utility, insurance, and oil & gas company-blaming comms approach. / end rant

DEEP DIVE — TIME TO ENGINEER A MORE STABLE CLIMATE

The world has sustained 1.5°C of warming above pre-industrial levels for over a year now. There’s no sign that trend will change anytime soon. Put plainly: We’ve run out of time to ‘do’ decarbonization without additional help to cool the planet now and buy time.

The Paris Agreement—with its lofty goals of keeping warming “well below 2°C”—is starting to look more like a polite diplomatic exercise than a genuine rescue plan. Despite pledges and targets, the energy transition simply isn’t happening fast enough. 82% of global primary energy is still fueled by oil, gas, or coal, and that number has only fallen marginally in recent decades.

Why CO₂ removal alone won’t save us

Many have pinned their hopes on dramatic emissions reductions across sectors (mind you, emissions of most if not all major greenhouse gasses globally remain at all-time highs) coupled with carbon dioxide removal (CDR): Capturing CO₂ from the air. The hard truth is that that approach is too expensive and too slow to cool the planet in time.

• $330/ton: The average retail price for removing 1 ton of CO₂ through today’s carbon removal projects.^† Note that many of these companies are likely charging less for removal than their hard costs!

• $3.58 billion: Spent so far on CO₂ removal, according to CDR.fyi.

• 13.2 million tons of CO₂ have been sold, but only 4.5% of that has actually been delivered. Even if all of it were delivered, it would offset less than Nepal's annual CO₂ emissions (not a big or emissions-intensive country, mind you, and again, that’d just be for one year!).

• Meanwhile, we pumped out over 37 billion tons of CO₂ in 2023 and have accumulated a debt of over 1 trillion tons of CO₂ since the industrial revolution—orders of magnitude more than we’re sucked up.

For most companies, trying to offset all of their emissions at $330/ton would be a fast track to bankruptcy. Even the target price of $100/ton of CO₂ removed would cripple most major companies. As a result, the advanced market commitment that was supposed to turbocharge the voluntary carbon market hasn’t come close to bridging this gargantuan gap, at least not yet. We wish them luck!

Bottom line: Today’s CO₂ removal industry will not meaningfully change global temperatures before 2100, and we shouldn’t put all our eggs into one basket. Could carbon removal scale? Sure. But public (and frankly, also private) sector commitment and will to accelerate that effort is nowhere near where it was even two to three years ago. Should people working conscientiously on scaling carbon removal stop? Hardly. But we’ll benefit from more toolkits in our toolbox, especially ones that would slow warming much more quickly than carbon removal can.

 † Aggregate price index of 1 ton of CO₂ removal sold on CDR.fyi as of December 2024

We already geoengineer—we just do it poorly

Humanity has been unintentionally geoengineering Earth for centuries. Greenhouse gases (GHGs) warm our planet, while sulfur aerosols cool it. Emissions from coal, shipping, and heavy industry have spewed sulfur dioxide (SO₂) into the lower atmosphere (troposphere), creating reflective particles that mitigate some CO₂-driven warming—albeit with severe side effects, including acid rain and others that are harmful to human and planetary health.

SO₂ emissions already peaked in 1979:

By 2022, we’ve cut SO₂ emissions by 48.5%:

The unraveling of our “messy sunscreen”

As governments cracked down on acid rain in the 1980s and 1990s via policies like the Clean Air Act, SO₂ emissions dropped. More recently, the International Maritime Organization forced ships to reduce emissions of SO₂ by scrubbing out the proverbial “sunscreen” from shipping emissions (IMO2020). While that’s welcome news for forests and your lungs, to which SO2 can be harmful, it also inadvertently reduced the reflection of solar energy significantly, yielding even more net global warming.

As pollution controls kicked in, we ironically reduced this unintentional “cooling shield.” According to climate scientist Zeke Hausfather, if it weren’t for aerosols originating from human activity, we could be close to 2°C of warming already. Slashing SO₂ emissions to protect ecosystems and human health has allowed more CO₂ warming to “shine” through.

Here’s another way of visualizing this from Nat Bullard’s annual energy transition deck:

For centuries, we have used SO₂ to cool the planet, but we have done so haphazardly and inefficiently. Stratospheric aerosol injection (SAI) proposes doing it cleanly and strategically, focusing especially on getting the SO2 into the stratosphere for longer-lasting, more controlled results.

The Pinatubo clue: Location & quantity are key levers

In 1991, Mount Pinatubo in the Philippines erupted, injecting ~20 million tons of SO₂ into the stratosphere, ~20 km (~12.5 miles) above the Earth’s surface. The result? A 0.5°C drop in global temperatures for roughly a year.

This reveals a critical truth: Location—specifically, height and quantity of SO₂ injections—matter enormously. A fraction of sulfur in the stratosphere can achieve the same cooling as far larger amounts of SO₂ closer to ground level.

1:1,000,000 leverage

With carbon removal, you remove 1 ton of CO₂ to counteract 1 ton of CO₂ emitted—a 1:1 ratio. It’s necessary in the long run, but it’s expensive and slow-moving.

Meanwhile, stratospheric aerosols last longer and disperse more globally because of the Brewer-Dobson circulation—which basically outlines the intricacies of how winds in the stratosphere keep SO₂ aloft for 1-3 years. Hence, you need far less SO₂ to achieve the same cooling effect vs. the troposphere. One gram (weight AND cost of a US dollar bill) of SO₂ in the stratosphere offsets the warming of 1 ton of CO2 (weight of a Toyota Yaris) for a year at an astonishing 1:1,000,000 ratio. That’s real leverage.

No, it’s not “permanent” in the way that avoiding the emission of carbon dioxide—which lingers in the atmosphere for hundreds of years—or carbon removal with long-term sequestration is. But carbon removal has its own durability and permanence issues; SAI is higher leverage and cheap, thus lending itself to iterative application, as needed, offering humanity more time to decarbonize (which will take many more decades).

How we started + where we’re going

Make Sunsets was born from the realization that we’re already geoengineering—just badly. We figured, let’s do it more carefully, ethically, and under public scrutiny.

Here’s our journey so far:

• First Micro-Launches: We began by releasing just 1 gram of SO₂ in Nevada, testing balloon delivery, and measuring data.

• Current Deployments: We deploy around 1,500 grams of SO₂ at a time. This is still a blip on a microscope compared to continuing SO2 emissions globally. Still, it’s enough to demonstrate feasibility while complying with US regulations and raising awareness by engaging with various media outlets. Want to see how it works? Watch here.

• Scaling Plans: With demand, we can scale up to 1,000 kg (1 ton) of SO₂ per balloon. That single launch could offset the warming effect of 1 million tons of CO₂ for a year. Extend the logic further, and 37,000 of these balloons could pause warming for 1 year. Scale would also help us reduce costs as we can buy sulfur at cheaper market prices ($100 to $200 per ton) if we buy in bulk.

• Radical Transparency: From cost breakdowns to financial health, we share everything monthly on our blog and FAQ. We’re not hiring PR firms that forgot to tell the mayor of the city that they’re spraying chemicals off a death machine or secret launches using "proprietary particles.” 

We’ve built a passionate community: 840+ customers—including atmospheric scientists, climate researchers, engineers, teachers, doctors, lawyers, accountants, a co-owner of an NFL team, billionaires, VCs, students, founders, and "climate dads"—have purchased Cooling Credits, offsetting the warming of 123,808 tons of CO₂ for a year.

Sure, that’s a drop in the ocean compared to total emissions. But it’s a real, measurable start—something no government, university research group, or corporation has done in SAI at this scale. And, let’s be real—while many CDR companies have raised hundreds of millions, we’re just two guys with under $2M in VC funding—yet in 2024, we delivered more cooling than any CDR company in the world.

The Economic Case: Yes, SAI is like sunscreen—it requires reapplication.

But, comparing costs:

• SAI: $1 per ton-year—renewed annually until CO₂ exits the atmosphere.

• CDR: $330+ per ton upfront—to remove a single ton permanently.

Cost & permanence: SAI vs. carbon removal methods

Despite the hype around carbon removal, permanent CO₂ capture remains expensive and slow-moving. Below is a short comparison of common CDR pathways alongside SAI:

*Costs vary widely by project scale, location, and technology maturity.

How can SAI be so cheap?

1. Fast & Scalable: We don’t need massive plants that consume vast amounts of energy or complex pipelines. We just need balloons (and eventually planes), people (come volunteer if you like!), and capital to deploy aerosols.

2. Bulk Sulfur Prices: Once you’re purchasing sulfur in tonnage at market rates ($100–$200/metric ton), the per-ton-year offset cost can drop well below $1. One ton of SO2 in the stratosphere can offset the warming of 1 million tons of CO2 for a year.

3. Small Injection, Big Effect: Releasing a tiny amount of sulfur in the stratosphere yields significantly more cooling benefit than larger amounts deployed near ground level.

SAI’s “catch”: Again, it’s like sunscreen. You have to keep doing it. If you stop injecting aerosols, the cooling effect fades over a couple of years, unlike permanent CO₂ removal options that lock carbon away for decades to millennia. Plus, there are many other potential externalities to evaluate → read on for more on that two sections down.

Measuring our progress: Present to future

Near-Term:

• Weather Balloons: This is our current method to deliver SO₂ to stratospheric altitudes cost-effectively. Again, you can see it work in action here:

• Monitoring: We measure the amount of SO2 in the balloon and track its location to confirm deployment in the stratosphere—not rocket science.

Long-Term:

• Aircraft Deployments: Once we’ve maxed out on balloons, we can use larger planes that can reach the stratosphere to inject bigger loads of SO₂ more efficiently and in precise locations.

• Satellite Validation: As we scale, agencies like NOAA can measure aerosol distribution from space, using the same satellites that measure the cooling effect of stratovolcanic eruptions.

• Refined Models: With real-world data, we’ll help hone climate models, track just how big or small SAI’s effect can be under different conditions, and get off the modeling treadmill with better and better data.

It’s all tradeoffs, all the way down

Nick’s note here: Make no mistake, none of this is riskless or a cure-all. As articulated by David Keith and Anthony Harding:

All “climate” solutions come with tradeoffs all the way down. Here’s more on SAI’s “harm-to-benefit” ratio from the above authors, with links to more sources.

So, what do we do now?

1. Acknowledge We’re Already Geoengineering: The history of societal progress has been and is predicted on burning things, whether wood, dung, or fossil fuels. That releases CO₂: Every day, we geoengineer. How we geoengineer today just happens to predominantly destabilize Earth’s climate system rather than stabilizing it or not impacting it drastically. There’s no going back to “pristine” quickly. But we can put on sunscreen. Or at least figure out how to make the sunscreen work at scale in case we need it at a later date. Plus, we may well discover other ancillary applications from the R&D along the way.

2. Take SAI Seriously. In addition to reducing emissions, SAI is perhaps the only proven approach that could scale quickly and drive immediate cooling.

3. Keep Investing in CO₂ Removal & Global Decarbonization, and other R&D: SAI might provide relief now. But, again, none of this is to say we won’t also need to remove the CO₂ from the atmosphere, develop atmospheric methane removal, and, most importantly, do the deep emissions reductions work globally (absent which, little else matters). It’s always and, and, and, ad infinitum.

From surpassing 1.5°C to the slow grind of global decarbonization or scaling up carbon removal, the current “climate” paradigm isn’t enough. Stratospheric aerosol injection offers a 1:1,000,000 leverage option, as one gram of SO₂ successfully deployed in the stratosphere offsets the warming of 1 ton of CO₂ for one year (at least). That’s not a get-out-of-jail-free card; it’s a bridge to buy time.

To recap, here’s why it’s worth placing SAI in the ‘climate’ mitigation toolbox:

• Near-Term “Bridge”: SAI can rapidly reduce warming now, buying time for global emission reduction efforts across industries and carbon removal (and other geoengineering) breakthroughs to catch up.

• Not a Substitute for Decarbonization: Because SAI doesn’t remove carbon, we still need to reduce emissions and invest in more durable CO₂ removal (and evaluate other early-stage GHG removal or ‘destruction’ methods).

• Inexpensive & Immediate: For any entity priced out by $300–$600/ton removal, SAI, at under $1/ ton-year, offers a compelling way to prevent additional near-term warming without waiting on game-changing tech or bankrupting budgets.

At the bare minimum, we should keep advancing this as a wrench in our holistic climate system restabilization toolkit. That’s why we make the noise. Even if we make enemies, moving the geoengineering conversation along alone is worth it. As Nick wrote recently:

As we proceed, we’ll continue to try to prove that we can genuinely impact the global thermostat in a measurable, relatively safe fashion. Join us for the next balloon launch and check out lots more content on our web (or Nick’s past writing: See here and here, for instance). Plus, we can always share many more resources for more learning).

Feedback? Pushback (desired!)? Comments? Respond and I’ll share with Andrew & co.

— Nick

More references & data sources

• CDR.fyi – Progress on Carbon Dioxide Removal Purchases

• Zeke Hausfather’s Analysis – Chart adapted by Nat Bullard. Shows anthropogenic warming at ~+1.33°C with aerosols offsetting around -0.57°C, for a net of ~+0.76°C at the time of that analysis. More recent data suggests we’ve passed +1.5°C in monthly or short-term anomalies. Exploring the drivers of modern global warming.

• Mount Pinatubo Eruption – Robock, A. (2000). Volcanic eruptions and climate. Reviews of Geophysics, 38(2). 

• Make Sunsets – Monthly Blog Updates

• IPCC AR6 – (2021) Sixth Assessment Report

• UNEP (2023). One Atmosphere: The Deep Interlinkage of Air Pollution and Climate Change.

• Keith, D. W. et al. (2017). Stratospheric solar geoengineering without ozone loss. PNAS, 114(12).

• Make Sunsets, Luke Iseman (2022). Calculating Cooling.

** Addendum on dead vs. live players from Nick’s intro: Dead, or at least only “half live” players, are kinda like Obama, who, after campaigning on his ability to be the real deal live player-wise and winning a dual House and Congressional mandate, surrounded himself with dead players—i.e., institutionalists, like Larry Summers. Thus, his admin achieved far less than it could have in the way of real reform, especially in banking. I say this as a quite liberal person overall, and a fan of Obama’s in general.