--> October 2021 – Jesse Reynolds / international & technology environmental policy

Solar geoengineering–long feared to undermine emissions cuts–may be able to enhance them

The leading concern about solar geoengineering–proposed technologies to block or reflect a portion of incoming sunlight to counter climate change–is that its research, development, and evaluation would obstruct already insufficient reductions of greenhouse gas emissions (“mitigation”). Although whether this would occur, how, and how we would know are uncertain and debated, the concern is real and continues to have impacts.

How mitigation obstruction could be prevented is likewise unclear. The only suggestion to date that strikes me as being potentially effective and feasible would be to link international policies of solar geoengineering with those of mitigation. This is the subject of my publication “Linking solar geoengineering and emissions reductions: Strategically resolving an international climate change policy dilemma,” now available (open access!) in Climate Policy. It builds on a paper by my former Emmett Institute colleague, Ted Parson, who provided essential early feedback on my new article.

International mitigation policy could be linked, first, with that of solar geoengineering research and development. This could entail some countries (which I assume the be the relevant actors) offering (preferential) access to their solar geoengineering R&D program to only those countries that mitigate more, an outcome that I consider synonymous with reducing mitigation obstruction.

Second, mitigation policy could be linked with that of whether to use solar geoengineering. This, in turn, could be done in four ways:

  • Countries could collectively agree beforehand to not use solar geoengineering unless they achieve some agreed-upon level of mitigation.
  • Countries could collectively agree beforehand to not use solar geoengineering unless climate change impacts are severe.
  • Solar geoengineering could be used soon at a small magnitude, just enough to generate useful knowledge and resolve some uncertainties. Its continuation would be made contingent on countries’ ongoing strong performance on mitigation.
  • One or more countries proclaim their right to use solar geoengineering only if and only if they meet their own mitigation goals and the rest of the world’s countries have failed to meet theirs. Inversely, the countries commit to forego that right if either of these criteria are not met. I call this “Authority to Act” linkage.

Finally, mitigation policy could be linked with that of how to use solar geoengineering. Here, only those countries that sufficiently mitigate may participate in collective decision-making regarding ongoing solar geoengineering, particularly setting its parameters such as magnitude.

In my “think piece” article, I explore each of these with respect to possible variations and whether they might be effective and feasible. I conclude that Authority to Act has substantial potential to increase mitigation while being consistent with countries’ apparent interests to join, comply, and enforce the agreement. The countries that proposed the linkage would be motivated to mitigate in order keep their option to use solar geoengineering (at least without suffering reputational damage from reneging on a commitment). The other countries would do so in order to prevent the proposers from deploying.

Although Authority to Act might be able to increase mitigation, it could fail to do so for a few reasons. Here, I’ll mention only the credibility of commitment of the the proposers. Whether they and the other countries mitigate enough yields four general possible outcomes:

Proposers mitigateProposers do not mitigate
Other countries mitigate[A] Proposers pledge to not deploy. Promise is credible, at least if goals are ambitious and climate change is not worse than expected.[B] Proposers pledge to not deploy. Promise is questionable, especially if climate change is worse than expected.
Other countries do not mitigate[C] Proposers retain right to deploy. Implicit threat is credible.[D] Proposers pledge to not deploy. Promise is relatively the least credible.

If the proposers meet their targets, then both the pledge to not use solar geoengineering if the other countries mitigate [outcome A] and the implied threat to use it if the latter do not [C] appear credible. If proposers do not meet their targets and the others do [B], then the credibility of the former’s promise to not deploy would hinge on climate changes impacts. If these were severe, would the countries capable of rolling out solar geoengineering not do so? Finally, if neither group meets the mitigation targets [D], then the promise would be the least credible.

Despite this and other limitations of proposals to link international mitigation and solar geoengineering policies, they can help advance the conversation about mitigation obstruction: whether it would happen, how, how we could know, and–perhaps most importantly–what decision-makers might be able to do about it. And such linkages might reduce the obstruction of mitigation, and even actually increase it.