Gernot Wagner - Geoengineering

The Paris Agreement has been widely hailed for breathing new life into sluggish global climate negotiations. Nobody thought it would solve climate change. Nothing can, by itself. But the Agreement clearly did show some momentum in the right direction and, after a four-year hiatus here in the United States, the pendulum is once again swinging hard in the right direction, hopefully without avoiding the swing back. All of that momentum toward more ambitious emissions cuts is clearly good, and nothing should take away from it!

While somewhat ironic then, it is precisely against this backdrop of increased global ambition to cut CO 2emissions in the first place, and a broader understanding of the importance of serious climate action, that solar geoengineering should be discussed.

It must not be either–or. The best approach is a balanced portfolio, where solar geoengineering might have some, at most temporary, role in mitigating the worst effects of climate change, while the world cuts CO 2emissions rapidly – to zero, and then some. 15

Such a balanced approach may well be wishful thinking. If history – and not just climate history – is any guide, it almost surely is. Fundamental forces hold the world back from doing enough to cut CO 2emissions. Those same forces push the world to do too much when it comes to solar geoengineering.

1 1 See Broecker (1975).

2 2 See Revelle et al. (1965). This report is often billed as the first ever report to a president on climate change. In fact, John F. Kennedy, too, received a (brief) climate change warning, and so has every president since (Hulac, 2018).

3 3 Budyko’s proposal first appeared in Russian (Budyko, 1974), subsequently translated into English (Budyko, 1977). See Caldeira and Bala (2017) for a brief history of the idea. Morton (2015) reviews the history in depth.

4 4 See National Research Council (1992).

5 5 See Crutzen (2006).

6 6 See Navarro et al. (2016).

7 7 See Cicerone (2006).

8 8 The clothing example is imperfect for another reason. The additional heat absorbed by black outerwear is typically lost before it reaches the skin. See Shkolnik et al.’s (1980) aptly named Nature study: “Why do Bedouins wear black robes in hot deserts?”

9 9 See e.g. Ocko et al. (2017).

10 10 See The Economist (2008).

11 11 See e.g. Goodell (2017).

12 12 Keith (2000) first mentions the three core characteristics. Keith, Parson, and Morgan (2010) first mentions the exact phrase: “fast, cheap, and imperfect.” Parson and Ernst (2013) explores its governance implications, Moreno-Cruz, Wagner, and Keith (2018) its formal economic implications, and Mahajan, Tingley, and Wagner (2019) U.S. public opinion of these characteristics.

13 13 See table 2 in Smith and Wagner (2018). Also see Smith (2020) as well as Lockley, MacMartin, and Hunt (2020).

14 14 See Gingrich (2008).

15 15 See Baker and Wagner (2016), and Moreno-Cruz, Wagner, and Keith (2018) for a formal exploration.

Solar geoengineering turns everything we think we know about climate change and climate policy on its head. For one, there is the link between CO 2concentrations 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. 1More 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 CO 2in 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.

Economics 101 is clear about the cause of excess CO 2emissions in the atmosphere: the benefits of emitting CO 2are privatized, while the costs of one’s pollution are largely socialized. The solution is self-evident: price CO 2at 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. 4The 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 CO 2. 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 CO 2cuts. 5But it surely is one part of the fuller picture.

Much as the free-rider effect implies too much CO 2pollution, 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. 6We 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. 7Whatever 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,” 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 4will 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. 9Those 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.