Can solar geoengineering be tailored to reduce inequality?

Guest Post by Ben Kravitz, Assistant Professor, Indiana University / January 21, 2019

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One of the things I like most about researching solar geoengineering is how researchers from many different subject areas work together on interdisciplinary problems. As a physical scientist, I rely on governance researchers to help prioritize the most important uncertainties in the field and, as such, guide my focus. In turn, I can provide governance experts with information about what aspects of solar geoengineering are likely to need governing.

This collaboration has revealed that one of the trickiest aspects of solar geoengineering is its potentially unequal effects. Our latest research shows that, to some extent, we could address this problem by design.

In general, simulations of solar geoengineering indicate that, for many climate variables (temperature, precipitation, sea ice, etc.), a world with high greenhouse gases and geoengineering looks a lot more like the present-day than a world with high greenhouse gases and no geoengineering.

But solar geoengineering is not a perfect substitute for reducing greenhouse gases, meaning there would be different effects in different places, leading to the potential for winners and losers. That in turn raises numerous questions about geopolitical negotiations, international justice, soft power, and compensation, among many others.

There is also the possibility that if negotiations over solar geoengineering sour, it could lead to conflict and destabilization. Reaching a global agreement on how much to cool the planet seems like a daunting task with perilous consequences for getting it wrong.

Faced with this challenge, the question arises: could we improve this technology to reduce its unequal impact?

My research on this topic involves using climate models to conduct simulations. Although imperfect tools, these models allow us to look at what could happen if the climate were to be modified, but without actually modifying the climate. For example, if we want to see what might happen to temperature and precipitation as a result of putting 10 megatons of sulfur in the stratosphere, we can use a model to understand where changes could occur and why.

Our recent research direction treats solar geoengineering as a design problem — that is, something that can be (somewhat) tailored. As an example, the effects of stratospheric geoengineering depend on where the particles are, when they are injected, how much is injected, and what the particles are made of.

We have shown that instead of just cooling the planet (i.e., global average temperature), it may be possible to cool one hemisphere more than another, which could shift tropical precipitation. Or it may be possible to cool the poles more than other parts of the globe, to help prevent ice melt and sea level rise. We don’t know yet, but it might even be possible to target specific regions, specific seasons, or variables other than just temperature.

This has potentially big consequences for solar geoengineering governance: the more things that can be controlled, the easier reaching an agreement might be.

This is not to say we have all the answers. It seems unlikely that someone could design a solar geoengineering strategy that makes everyone happy. It’s not a personalized thermostat.

Moreover, there are fundamental limitations in the climate system; for example, one cannot wall off the stratosphere, so the location of stratospheric particles is not perfectly controllable. As such, there is likely an upper limit as to how many objectives can be met. We don’t understand this range, or put more simply, we don’t yet understand what solar geoengineering can and cannot do.

But based on the latest research, it seems as though there is more to solar geoengineering than bluntly reducing global warming. There is some potential to tailor its effects to specific governance requirements, and that might be one piece of creating a more level playing field for everybody.

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