When Do We Know Enough to Say Stop?

There is a large and growing mountain of literature about solar geoengineering that clearly expresses the conclusion that an advertent, planetary-scale manipulation of the Earth’s reflectivity is a very risky and uncertain endeavor. Here on this website you can read about many of the risks and potential adverse side effects, which are legion. You can also add your name to a proposed agreement not to deploy solar geoengineering.

My intention with this blog entry is not to try to make the mountain of evidence even larger, but rather to explore the question of how to determine when we have enough scientific information about a subject to say that we know enough to stop?

In November 2023, my colleague and friend Victor Galaz and I were asked to be part of a live discussion of the topic of geoengineering on Swedish television’s evening news broadcast. Victor and I had previous experience on live TV, and I think both of us were looking forward to having some time to explore this important topic for the general public. In pre-interviews ahead of the broadcast it was established that while both Victor and I were dead set against any deployment of solar geoengineering, we had different opinions about whether further research on the topic was useful. Once we were in the studio, both Victor and I felt blindsided by the presenter, since a several-minute-long video clip about various different forms of geoengineering was shown before we were asked for comments, and neither Victor nor I had seen or even been informed of its content. While the presenter did state a few times during the discussion that we both were against deploying solar geoengineering, he definitely kept our difference of opinion about the utility of research on the topic front-and-center. Victor and I both tried to salvage the discussion as best we could, keeping our remarks and comments focused on science.

So, what was our disagreement?

Victor’s position was that obtaining deeper knowledge about the potential side effects associated with solar geoengineering would give all of us – and future generations – an even better basis to make well-informed decisions about how to deal with the issue. That is what science does best. We gather, evaluate and present evidence impartially, and gain deeper knowledge about how the Earth system works.

My own opinion was that we already have sufficient information about solar geoengineering to draw the conclusion that it is a very bad idea, and should be abandoned. I didn’t feel we needed to gather yet more information on the topic so that we would be able to conclude that the idea is not just bad, but dreadful, appalling, undesirable, harmful, dangerous, deleterious and unwholesome. I felt that reaching the conclusion that the idea is bad was sufficient, and we could move on to do research on some other important topic.

This opinion goes very much against the grain of my scientific training, and in many ways it really stings. Like Victor, I’ve been trained to view scientific knowledge as a public good. More of it, almost by definition, should increase the value of this public good. More knowledge can’t be a bad thing, right?

Bad, very likely not. Unnecessary, perhaps.

We’ll have to move off into the weeds a bit to try to discover the roots of this somewhat heretical opinion.

First, let’s explore the nature of the words that have been used to give a name to the topic: Solar Radiation Management. To me, these three words express colossal hubris. They imply we can successfully manage solar radiation. Really? Look at how well we are managing atmospheric CO2 concentrations after decades of knowing that they are too high. Next, further research on this topic will contribute to its normalization in the public eye. Even if the scientific results continue to show it is a boneheaded idea, the simple fact that research is being done on the topic can be used by those who support it as evidence that the idea itself is dignified.

Who are the supporters of this idea? Recent research has indicated that supporters have close ties to US financial and technological capital, as well as a number of billionaire philanthropists. What seems to unify these actors is the apparent belief in an “Ecomodernist Manifesto” – letting the free-market system develop technologies that will decouple economic growth from environmental harm. We can grow ourselves out of trouble, and technology will save us. As an experimentalist, I’m a strong believer in the power of technology. My colleagues and I try very hard to develop new technologies to help us better understand how the Earth system works. Still, taking the leap to believing that technology itself will be a Messiah for our global challenges is something that I cannot do. Technology without wisdom can be a very dangerous thing – and I really don’t think we are sufficiently wise yet as a species to be futzing around with planetary manipulations.

Finally, one of the main arguments for researching this issue – that it might “buy us time” to figure out how to reduce emissions – has been shown to be false. Even if successful in stabilizing surface temperature, as long as we continue to add CO2 to the atmosphere, we continue to worsen the problem of ocean acidification. As long as we continue to add CO2 to the atmosphere, we make the problem of “termination shock” (the extremely large and rapid increase in surface temperature that will happen if the solar geoengineering manipulation is ended) ever more catastrophic. Once started, we will need to deploy this technique until the time at which we have removed enough CO2 from the atmosphere to be within the climate planetary boundary. We would simply be replacing our addiction to fossil fuels with an addiction to aerosol particles. I can’t help but wonder whether one of the reasons that this kind of approach is appealing to tech entrepreneurs is that if you can stimulate and then corner the initial market on Solar Radiation Management, you will have job for which you can charge pretty much whatever you want for any foreseeable future.

Coming back from the weeds, where does this leave us? The very clear conclusion from the climate research community is that we must stop emitting CO2 and other greenhouse gases to the atmosphere. We must also develop technologies to take a fair amount of the CO2 we have emitted to the atmosphere and put it back into the geological domain in an environmentally and socially responsible way. These two conclusions are pretty much no-brainers.

What I hope to stimulate with this blog is a discussion of a thornier issue. When (if ever) should we choose not to obtain deeper knowledge about an issue? At what level of understanding can we say that we have enough information to make well-considered, evidence-based decisions? When do we know enough to say stop? This blog has considered one scientific issue for which these questions may be appropriate, but there are lots more. Recent developments in genetic manipulation and artificial intelligence lend themselves to similar consideration. There are of course no black-and-white answers to these questions. I hope we can have a rich and colorful discussion about them.

Kevin Noone is professor of chemical meteorology at the Department of Environmental Science and the Bolin Centre for Climate Research at Stockholm University. He has done experimental research on atmospheric aerosols and clouds since the early 1980s. He is currently involved in the field of community science, and is active in trying the reduce the gap between science and society. He has been Executive Director of the International Geosphere-Biosphere Programme, founding Director of the Swedish Secretariat for Environmental Earth System Sciences, Editor-in-Chief of the Community Science Exchange, and Chair of the Thriving Earth Exchange of the American Geophysical Union. He is currently Chief Scientific Advisor for two economic think-tanks – the International Sustainable Finance Centre and Re-Define.

Disclaimer: The views expressed in this blog are personal.

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