Gernot Wagner has spent a large part of his life thinking about solar geoengineering, and even he thinks it is “nuts”, as he says in the first line of his book. Geoengineering is usually defined as large-scale interventions in our climate. Here, although Wagner refers briefly to carbon removal and natural climate solutions such as tree-planting, he is mainly concerned with solar geoengineering (also called solar radiation management), where aerosols would be deployed into the stratosphere to reflect sunlight back into space and reduce the amount of heat coming in. The comparison he returns to most often is that of the ash from a volcanic explosion.
It is a concept that has been around since the 1960s, when scientists first warned politicians about the possibility of global heating. But as evidence piled up that this warming really was happening, there was concern that geoengineering would seem like a cheap fix, and would distract people from the serious business of cutting carbon emissions. For this reason, Wagner writes, there was a “long‑standing, self-imposed, unspoken near-moratorium on solar geoengineering research within the scientific community”.
It turns out, of course, that it didn’t take much to distract humans from cutting carbon: despite international promises, starting with the Kyoto protocol in 1997, our emissions have continued to rise. In 2006, Nobel laureate Paul Crutzen published a scientific essay arguing that humans might need an “escape route” if climate change got out of control, and geoengineering was put on the table again. In 2015, Wagner and David Keith, a Harvard scientist who has been at the forefront of the climate engineering discussion, agreed to set up Harvard’s solar geoengineering research programme.
Would it work? All the evidence suggests that solar geoengineering would be “fast, cheap and highly imperfect”, notes Wagner. Based on studies of the effects of various volcano eruptions, plus the research they have done so far at Harvard, it could if properly deployed “help lower global average temperatures within weeks and months” at a cost of billions of dollars rather than trillions. The eruption of Mount Pinatubo in 1991, for example, lowered global average temperatures by about 0.5C within a year.
Solar geoengineering could also – this is the highly imperfect part – have a long list of downsides. They include its possible impact on rainfall, leading to drought and thus potentially millions of deaths; ozone depletion; continued ocean acidification; impact on plants and whitening of skies. Then there is the governance issue: who would be in charge of the programme? What would be the best way to run such a thing?
As if all this were not bad enough, there is the very real fear that having geoengineering as an option will reassure people that they need not bother to reduce carbon. Wagner emphasises over and over again that the only serious and lasting way to deal with the climate crisis is to reduce emissions: “Nothing else will do.” He and the scientists he works with do not regard solar geoengineering as a replacement for mitigation, but as, possibly, something that may buy us a bit of time while we are cutting emissions, or if we fail to cut enough in time and hit disaster.
He passionately believes, however, that we should be doing the research now. “What often keeps me up at night … is the fear that we might be slithering towards deploying solar geoengineering without having done the hard work.” He looks back at our history of cutting carbon and is not optimistic. “At what point did not cutting enough CO2 turn from an error of omission to an error of commission? If we believe we’ve passed that point – and I certainly do – at what point then does something similar apply to geoengineering?”
It’s hard not to feel sceptical going in, but Wagner is transparent about his own position from the beginning: “One does not need to like solar geoengineering to take the idea seriously,” he says. “I don’t like it.” In return, we, the sceptical readers, must concede that his grounds for concern – that humans may not take sufficient action on carbon – are fair. It is with deep horror that I find myself thinking, by the end of the book, that he at least deserves a hearing.
