The results are in: discussing solar geoengineering doesn't undermine emissions cuts
There have been over a dozen public perception studies on solar geoengineering, and they are clear: the fear that motivated the taboo on solar geoengineering research was unfounded.
About a year after I started my PhD in 2009, I was invited to be an expert at a public dialogue on carbon dioxide removal and solar geoengineering. The UK was considering launching a research effort and wanted to know what the public thought about it [1].
The participants were given an overview of all the various ideas and then asked to discuss them with the help of a moderator. Generally, the more "natural" a proposal seemed, the more supportive the public was: afforestation was very popular, stratospheric aerosol geoengineering was not. But, while the participants were concerned about many of the ideas, they were very supportive of research.
I remember one older guy speaking to me on the side: "Are scientists seriously thinking about this? Wow, climate change must be worse than I thought." I got the sense then that this was a widespread feeling.
Breaking the taboo
The Royal Society had recently published a report recommending that a major research effort into carbon dioxide removal and solar geoengineering begin and the UK’s research councils wanted to check that the public would support this research. They concluded that they did and so they launched the world's first nationally-funded research effort.
These ideas hadn't just occurred to scientists in the late 00’s, many of them had been around for decades, but they had been suppressed for fear of distracting the public and policymakers from cutting CO2 emissions [2]. It took the intervention of Paul Crutzen, winner of the Nobel Prize for his work on the ozone layer, to break this taboo [3].
16 years on from Crutzen's intervention it seems clear that the fear that motivated this taboo on solar geoengineering research was unfounded.
Moral hazard
Many reasonable people oppose solar geoengineering on the grounds that it might undermine mitigation efforts, delaying the date that we achieve desirable cuts in emissions. This possibility is known as the moral hazard effect or mitigation deterrence effect.
There’s a lot to say about this idea, but I think a useful place to start is to distinguish a strong and a weak moral hazard objection to solar geoengineering research:
"Discussion of solar geoengineering will lead to a reduction in emissions cuts"
Weak: "Implementation of solar geoengineering will lead to a reduction in emission cuts"
While it's obviously too early to know much about the effects of implementing solar geoengineering on climate policy, we're now in a position to dismiss the strong moral hazard objection to solar geoengineering research.
The results are in
So far there have been 13 studies assessing how the public responds to solar geoengineering that can shine a light on this issue (see the Appendix). Only one study, Raimi et al. (2019) found a reduction in support for emissions policies after telling their participants about solar geoengineering, and they only got that result when solar geoengineering was 'described as a "great" solution to climate change, one in which "we wouldn't have to do much more to stop the worst effects of climate change."' In their other 2 framings of solar geoengineering, they found no statistically significant effect on support for emissions policies.
For the other studies, 7 found no significant effect, and 5 found an inverse moral hazard effect, i.e., exposing people to the idea for solar geoengineering increased their apparent willingness to cut emissions. Merk et al. (2016) was the first study to document this inverse moral hazard. For their study, they gave 650 German participants 10 euros each, gave them some reading, surveyed them, and then offered them the option to buy subsidised carbon offsets. Some were told about stratospheric aerosol geoengineering and others weren't. Those who were spent 15% more on carbon offsets than those who weren't. This wasn't simply virtue signalling, they spent real money.
Now, the approaches of these various studies differ a lot, but it seems that when the study focuses on people's own response, they tend to find more of an inverse moral hazard effect, and when they ask about what other people are likely to do they tend to find a null result.
There have been concerns that climate-skeptic conservatives may flip to promoting solar geoengineering as an alternative to emissions cuts. A few of the studies analyse the political character of their participants and find that those who are more egalitarian and communitarian (left-leaning) are more likely to show an inverse moral hazard effect and those who are more heirarchical or individualistic (right-leaning) tend to show no effect or a modest moral hazard effect (E.g., Corner and Pidgeon, 2014, Kahan et al. 2015). However, in their US study Mahajan et al. 2018 found that self-identifying republicans were far less supportive of solar geoengineering research and use than their democratic counterparts (see the figure below).
Figure 1. Support for solar geoengineering use (a) and research (b) by US party affiliation. Figure 3 from Majahan et al. 2018.
Interestingly, Fairbrother (2016) found in their UK survey that while exposing people to solar geoengineering didn't change their support for a climate tax, it did substantially increase conservatives trust in climate science. He reasoned that this suggests that conservatives are primarily skeptical of government taxation, and that by showing that tax-neutral climate policies like solar geoengineering are being considered, this suggests to them that climate science is more trustworthy than they thought.
Discussing solar geoengineering has not led to a reduction in emissions cuts
The concern that motivated the taboo on solar geoengineering research makes sense in context. In the 90s and 00s there was very little progress on climate change and the merchants of doubt were successfully leveraging uncertainty to downplay the need for emissions cuts. It wasn’t unreasonable to worry that solar geoengineering might undermine fledgling climate efforts. But things have changed.
The world is now seriously grappling with climate change and many developed nations have driven down their emissions and have ambitious plans to eliminate their CO2 emissions by mid-century. Progress is slow and we're likely to see substantial warming and significant suffering before we eventually eliminate CO2 emissions.
This is why we need to seriously consider solar geoengineering – to reduce the inevitable suffering that climate change will bring as we work to eliminate our CO2 emissions.
The fear that even discussing solar geoengineering would undermine emissions cuts held back research for decades, but this fear has proven to be groundless. Public perception research demonstrates that the public isn't about to abandon efforts to cut emissions and may even become galvanized to do more when they hear that scientists are taking this idea seriously. It may also increase trust in climate science amongst those sceptical of taxation and government regulation.
Merely discussing solar geoengineering doesn’t undermine emissions cuts. It’s time to set that fear aside and build a better understanding of the potential, risks, and broader implications of this idea.
Appendix
Here’s how I’ve characterized the various public perception studies into the moral hazard effect. MH = significant Moral Hazard effect, No-MH = significant rejection of Moral Hazard effect, NULL = No significant effect, INVERSE = significant inverse Moral Hazard. I’ve also characterized them depending on whether they focus on the personal response of the participant or their views on the likely response of others.
Let me know if I’ve mischaracterized any in the comment section.
Corner and Pigeon (2014) - Personal: No-MH, others: MH.
Nick Pidgeon, personal comms: “people felt they would not be susceptible to moral hazard themselves, but politicians etc would!”
Kahan et al. (2015) Personal: NULL, skews towards inverse.
Slight increase in concern about climate change but not significant.
Fairbrother (2016) Personal: NULL.
Merk et al. (2016) Personal (money): INVERSE.
Wibeck et al. (2017) Personal: INVERSE
Majahan et al. (2018) Others: NULL, skews towards inverse.
They found a substantial acquisence bias, i.e., participants tended to agree whether you asked “will this lead to MORE emission cuts” or “LESS emissions cuts.”
Merk et al. (2018) Personal: NULL
Experts were asked how they would divide a budget, so not a direct test.
Raimi et al. (2019) Personal: NULL / MH
Null result, except when solar geoengineering was 'described as a “great” solution to climate change, one in which “we wouldn’t have to do much more to stop the worst effects of climate change.”'
Merk et al. (2019) Personal: INVERSE
Austin and Converse (2021) Personal: NULL
Cherry et al. (2021) Personal: INVERSE
They find the inverse effect is present among egalitarians and communitarians, but not among heirarchical and individualistic participants.
Andrews et al. (2022) Game (money): NULL
Cherry et al. (2022) Game: INVERSE
Other References
[1] Here’s a link to a case study on this “Experiment Earth?” public dialogue.
[2]