The case for delaying solar geoengineering research

by Halstead 7mo23rd Mar 201913 comments

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Tl;dr:

Argument:

1. Solar geoengineering is not feasible for the next few decades.

a. Solar geoengineering poses major governance challenges.

b. These governance challenges are only likely to be overcome in at least 50 years’ time.

2. Solar geoengineering research is a moral hazard, and research might uncover dangerous weather manipulation methods.

3. Given this risk and given that we can delay research without obvious costs, there is a good case for delaying solar geoengineering research at least for a few decades.

Epistemic status: Seems correct to me, but some expert disagree (though I don’t think they have been exposed to these arguments).


Solar geoengineering is a form of climate intervention that reduces global temperature by reflecting sunlight back to space. The best studied form - stratospheric aerosol injection - involves the injection of aerosols, such as sulphur, into the stratosphere (the higher atmosphere). This mimics the effects of volcanoes, which can have globally significant effects via the same mechanism. For example, the Pinatubo eruption in 1991 cooled large parts of the Earth by about half a degree. Computer modelling studies have suggested that, if done in a certain way and in certain climatic conditions, solar geoengineering could eliminate many of the costs of global warming without having serious side-effects.[1] These models are of course limited and crude, but they do suggest that solar geoengineering could be useful tool, if it could be deployed and governed safely.

Consequently, interest in the technology is increasing, as discussed in this Economist article. The Open Philanthropy Project has in the past funded solar geoengineering governance research and computer modelling efforts.

Here, I will argue that we should delay solar geoengineering research for a few decades.

1. Solar geoengineering is not feasible for the next few decades

a. Solar geoengineering poses severe governance challenges

In my view, solar geoengineering is only likely to be used once warming is quite extreme, roughly exceeding around 4 degrees. The reason for this is that solar geoengineering would likely be extremely difficult to govern. I outline some of the governance challenges in section 3.4 of my paper on solar geoengineering.

Solar geoengineering, if done using the stratospheric aerosol injection method, would affect the weather in most or all regions.[2] Solar geoengineering would therefore politicise the weather in all regions, and would have diverse regional effects. Adverse weather events would likely be blamed on solar geoengineering by affected countries, even if they were not in fact caused by solar geoengineering. Public anger at such weather events would likely be severe if they thought a massive international weather alteration scheme were at fault. Computer models could at best offer highly imperfect attribution of weather events to climatic causes.

This suggests that for solar geoengineering to be feasible, all major global powers would have to agree on the weather, a highly chaotic system. Securing such an agreement would be extremely difficult in the first instance and also extremely difficult to sustain in the longer-term. States would also foresee the problems of sustained agreement, disincentivising successful agreement in the first place.

b. These governance challenges are only likely to be overcome in at least 50 years’ time.

In light of this, solar geoengineering is only likely to be used once climate change is very bad for all regions. Judging when this point will occur is difficult, but my best guess having looked at the climate impacts literature in some depth is that this would only likely happen after about 3-4 degrees of warming.

We have had about 1 degree of warming thus far and, according to an IMF report, a further 1 degree of warming would be economiclly positive for many regions, especially Canada, Russia and Eastern Europe, and even potentially China (IMF report page 15).

(Note that even this modest climate change is bad overall for the world.)

Russia is a crucial factor here: global warming seems likely to bring numerous economic benefits for Russia, freeing up the Russian Arctic for exploration and thawing potential farmland. It is very unlikely that they would agree to a global scheme that would likely damage their economic prospects. Without agreement from Russia, I find it difficult to see how solar geoengineering could ever be implemented.

Thus, it seems implausible that solar geoengineering would be practicable at 2 degrees of warming, and 4 degrees is a more plausible threshold, in my view.

However, 4 degrees of warming will take many decades to occur. On the highest emissions scenario considered by the IPCC, 4 degrees of warming would take at least 50 years to occur (IPCC synthesis, p59).

This means that solar geoengineering is only likely to get used by around 2070, giving us 50 years from now to find a solution.

One potential counter-argument would point to runaway feedback loops that cause rapid warming, such as release of massive amounts of methane from clathrates. I have looked at the evidence for this and the evidence overall seems slim and the median view in the literature is that this is a negligible risk for the next century at least. See section 4 of my write-up on climate and ex risk for more on feedback loops.

2. Solar geoengineering research is a moral hazard and research might uncover dangerous weather manipulation methods

Research into solar geoengineering itself carries two main risks.

A persistent worry about solar geoengineering research concerns moral hazard: the worry that attention to plan B will reduce commitment to plan A. Having solar geoengineering as a backup will decrease commitment to reducing carbon emissions, which almost all researchers agree to be the top priority. The best discussion of this is in Morrow’s paper,[3] and I discuss the considerations on moral hazard risk at length in sections 4-6 of my paper. Overall, I think this is a genuine risk with solar geoengineering research and a reason not to carry out research.

Another risk of solar geoengineering research is that it will uncover new technologies that could destabilise global civilisation. I discuss weaponisation risks in section 3.2 of my paper. For example, climate researcher David Keith has discussed the possibility that a certain type of nanoparticle could be much longer lasting than ordinary solar geoengineering and so could potentially precipitate an ice age if deployed for long enough. I don’t think this particular technology could actually be a feasible doomsday weapon, but there is a concern that further research could uncover dangerous unknown new geoengineering technologies.

In a nutshell, for those persuaded by the Vulnerable World Hypothesis, research into technologies that could dramatically alter the weather seems like the kind of thing we should avoid if we can.

3. We should delay solar geoengineering research

Solar geoengineering research has clear risks and, given that we cannot deploy it at least for the next 50 years, there is no need to incur these costs now. Instead, the more prudent course seems to be to wait and see how well standard mitigation efforts go and then, if these continue to fail, start researching solar geoengineering in earnest around the middle of the 21st century. This would give us at least 20 years to cover the technical details and a governance framework. This seems to me like enough time, given that:

  • Solar geoengineering is probably technically feasible with adaptations to various different current technologies.
  • Extant insights from the governance of other public goods, free rider problems, and free driver problems, could in large part be applied to solar geoengineering, adapted to account for the features of that technology.

I at least don’t think that we need 50 years of forward planning to figure this technology out if we need to use it. Committing research hours when we know it may actually be used makes more sense when research risks undermining fragile commitment to mitigation, and risks discovering dangerous new technologies.

Note that my view has changed on this and that in my paper on solar geoengineering, I made a tentative case for primarily governance-focused research.

[1] For layman’s discussion of a recent paper, see this Vox piece.

[2] The reason for this is that the particles would be distributed globally by stratospheric winds.

[3] David R. Morrow, “Ethical Aspects of the Mitigation Obstruction Argument against Climate Engineering Research,” Philosophical Transactions of the Royal Society of London A: Mathematical, Physical and Engineering Sciences 372, no. 2031 (December 28, 2014): 20140062, https://doi.org/10.1098/rsta.2014.0062.

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