1 Not if, but when
Solar geoengineering turns everything we think we know about climate change and climate policy on its head. For one, there is the link between CO2 concentrations in the atmosphere and eventual global average temperatures, which itself is highly uncertain. The technical term for this link between concentrations and temperatures is “climate sensitivity.” A recent, comprehensive review has advanced our thinking there quite a bit and indeed narrowed the band of uncertainties; alas plenty of uncertainties remain.1 More on that topic, much more, in my prior book, Climate Shock, joint with the late, great Marty Weitzman.2
Most importantly for our purposes here, solar geoengineering breaks this link between concentrations of CO2 in the atmosphere and global average temperatures. It is the only potential climate policy intervention to do so. It also does so highly imperfectly. Solar geoengineering does not tackle the root cause of climate change directly. It does, however, tackle global average temperatures – quickly and cheaply.3
That, in a nutshell, is why solar geoengineering is not a question of if but when. There are few ifs and buts about it.
From “Free Rider” to “Free Driver”
Economics 101 is clear about the cause of excess CO2 emissions in the atmosphere: the benefits of emitting CO2 are privatized, while the costs of one’s pollution are largely socialized. The solution is self-evident: price CO2 at the difference between the marginal private and social cost. Arthur Pigou suggested as much in 1920, in his case for rabbits overrunning a communal meadow.4 The diagnosis is the same.
The term for this Economics 101 principle: the free-rider effect. It is in nobody’s immediate self-interest to go first and bear the costs of mitigating CO2. That goes for individuals and companies as much as it does for countries. Why commit to something if others won’t?
Economists arguably make too much of a deal out of this one element of the analysis. Political Economics 101 immediately points to vast vested interests as the true hurdle for action. Even if politicians in one country are citing other countries’ lackadaisical climate policies as a reason for their own inaction, it typically comes down to domestic politics. In short, the free-rider effect may be overplayed. It clearly isn’t the full explanation of what is preventing steeper CO2 cuts.5 But it surely is one part of the fuller picture.
Much as the free-rider effect implies too much CO2 pollution, solar geoengineering is governed by the opposite fundamental forces. It’s not about motivating to act, it’s about stopping too much action. Call it the “free-driver” effect. Marty Weitzman and I coined the term in a Foreign Policy essay memorably titled “Playing God.” Weitzman later formalized the idea in a peer-reviewed economic paper.6 We were by far the first to recognize this fundamental property and to consider it important. As is so often the case with game-theoretic ideas, the first mention goes back to Nobel laureate Tom Schelling.7 Whatever its name, the fact that solar geoengineering is such a potentially powerful tool relative to its costs makes it a force to be reckoned with.
“Free” is relative
“Free,” of course, is a slight exaggeration. Deploying solar geoengineering does come with costs. There are potentially large risks, unknowns, and unknowables.8
There are also costs for monitoring and guiding any deliberate, largescale solar geoengineering deployment program. The cost in both money and time is potentially large. That, too, is important – and ought to be a crucial part of any sensible solar geoengineering deployment scenario. Chapter 4 will attempt to paint such a scenario.
Here, I’m simply referring to raw deployment costs – the narrow engineering costs of actually doing the solar geoengineering. Those costs are what the free-driver effect captures, and they are indeed cheap – too cheap. But solar geoengineering is not free.
In fact, some of the best estimates put the costs of stratospheric aerosols in the single-digit billions of dollars per year during the early stages of deployment. That’s not nothing. It isn’t tens, or hundreds, of billions of dollars per year either. In short, done “efficiently,” deploying solar geoengineering at scale is within the purview of dozens of countries. The military budgets alone of around 35 countries are at least $5 billion, and 24 have budgets greater than $10 billion.9 Those estimates entail designing an entirely new plane capable of flying missions – sorties, in aerospace speak – to at least around 20 kilometers up and somewhere within plus or minus 30° latitude around the equator. The origin behind this number is instructive by itself.
Common lore has always been that stratospheric aerosols would be cheap, and that deploying them could be done easily. In fact, word in the (small) solar geoengineering research community was that it could be as simple as modifying a dozen or so existing jets. High-flying business jets could do the trick, invoking images of the crazed billionaire business owner taking the seats out of his Gulfstream – and voila.
The origin of this belief is a bit murky, but among the first to explore the topic in earnest was a study conducted by Aurora Flight Sciences, funded by David Keith with money from the Fund for Innovative Climate and Energy Research (FICER), which, in turn, had been provided by Bill Gates. (More on all this later, in Chapter 3.) The resulting report presented calculations for a New High Altitude Aircraft and also concluded that it might be as easy as modifying existing aircraft.10
Cue a couple of emails from one Wake Smith, sent out of the blue to David Keith and me around 2016, when we were in the early stages of developing what would turn into Harvard’s Solar Geoengineering Research Program. (More on that later, too, primarily in Chapter 3.) Wake introduced himself as having held, among many other accomplishments, the position of former President and Chairman of Pemco World Air Services, a leading airplane modification company. He clearly had a lot of expertise on the subject, he cared about climate change, and he wanted to try to be helpful. We met.
I began our first meeting in the way I tended to whenever I spoke to anyone with any kind of business or finance background: Ours was a research effort; commercial interest would be dangerous. And in any case, there was no commercial case here: “Have you heard of the free-driver effect?” Wake assured me he had no financial interest, but that he was, in fact, curious about the free-driver effect. He had read David Keith’s book and about how modified business jets could work. From David, verbatim:
Injection of sulfates might be accomplished using Gulfstream business jets retrofitted with off-the-shelf low-bypass jet engines to allow them to fly at altitudes over sixty thousand feet along with the hardware required to generate and disperse the sulfuric acid.11
Wake was skeptical. He didn’t want to say so directly, at our first meeting, but he clearly thought such a retrofit wouldn’t work. Or rather, that a more powerful engine implied a new plane, a new certification process, the works. For someone who used to run a company modifying planes, this seemed like a different exercise altogether: designing a new plane.
Wake set out to demonstrate that his initial reaction was correct. He spoke to engineers at Airbus, Atlas Air, Boeing, Bombardier, GE Engines, Gulfstream, Lockheed Martin, NASA, Near Space Corporation, Northrop Grumman, Rolls Royce
