Solar geoengineering to cool the planet: Not if, but when

Economist Gernot Wagner on a radical solution that’s no longer science fiction

Controlling the world's changing climate with the use of geoengineering is thought to be fraught with risks. Imagine a rogue actor taking control of the climate, impacting the weather, storms, and rainfall with implications for the global economy and society in general – the stuff of James Bond villains in the Putin era.

But many researchers and politicians argue geoengineering as a very real solution. Solar geoengineering in particular, the notion of cooling Earth by reflecting sunlight back into space, is increasing in popularity. But this ambition would require huge global coordination.

Austrian researcher Gernot Wagner is a climate economist, academic and author who describes himself as a reluctant proponent of geoengineering. He is the founding co-director of Harvard's Solar Geoengineering Research Programme.

In his recent book, Geoengineering: The Gamble, he provides his take on the possible benefits and risks of various approaches, especially the so-called “moral hazard”; that researching or even discussing geoengineering would undermine the race to cut carbon emissions in the first place.


Despite those risks, he argues that an era of solar geoengineering may be an inevitability – not a question of if, but when – and a crucial component of what he terms climate economics. This interview was conducted via video call.

What is a climate economist?

A walking living oxymoron, right? Not too long ago, when I told people I am a climate economist, the first response was generally one of confusion. You can either worry about interest rates and unemployment, or you worry about birds, bees and the climate scenario – but not both.

I don't know what changed over the past few years. Obviously, it depends on the country and I feel that Ireland and some other countries European nations grasped this earlier, but in many other places, like here in the US, that change happened much more recently, where suddenly it's become completely obvious that the climate is such an all-encompassing issue that it is completely related to the economy.

So let’s call the climate economist the person who can help guide market forces in the right direction to tackle the challenges of the 21st century. Climate economics is about focusing on pricing climate risk and figuring out what to do about it.

What are the key ideas around geoengineering?

Geoengineering is a kind of stepchild of climate policy, and frankly it should be, for good reason. Step one in climate policy is to coordinate how we cut net carbon emissions to zero. Step two is adapting properly – adapting to what’s already in store. That’s where geoengineering comes in.

We’ve been beating the drum about cutting carbon emissions forever but we haven’t solved climate change yet. So geoengineering is this notion of altering the atmosphere so as to reduce the impact of a rapidly changing climate. Carbon capture is one example where carbon is literally sucked out of the air.

It’s technically possible and is already being used at small scales, but is very expensive. A cheaper solution, but one which is more controversial – and is the focus of most of my work – is solar geoengineering, an approach which aims to reflect sunlight, that is to say, energy and radiation, back into space in an attempt to cool the planet.

How does solar geoengineering work in practice?

Well, the idea is to deliberately release millions of tonnes of very small reflective particles into the lower stratosphere, which act together to reflect just enough sunlight to cool the Earth to a desired level. We know that it will work because volcanoes have been doing this since time began.

'Solar geoengineering is not happening yet, but there has been quite a lot of research in that direction and the technology is essentially ready to go'

When a volcano erupts, it sends up all these particles into the atmosphere, eventually causing a cooling below due to their reflective properties. The difference in the case of solar geoengineering, of course, is that there is no violent explosion. It’s important to note that solar geoengineering is not happening yet, but there has been quite a lot of research in that direction and the technology is essentially ready to go.

How would this work economically?

Economically, the idea would translate to a very low-cost solution relative to unmitigated climate change on the one hand, which of course, in many ways is the most expensive thing we can do.

That is what we are currently doing, by the way, not cutting carbon emissions by enough. On the other hand, solar geoengineering is also low cost relative to cutting emissions. Those are the attractive properties of the approach: it is cheap and it is fast, the results realised within weeks and months. That means it could be very important in the future.

Are there sufficient avenues for realistic international cooperation?

At a high level we already have the structures in place to allow world leaders to talk to each other and come to agreement on things that are, frankly, highly controversial. We already have organisations like the UN's Security Council and General Assembly. We have bilateral diplomacy and the G20.

We have the UN climate talks and the UN Environment Programme. We have these forums where more than 190 countries come together and solely talk about the environment. So I think there should be no problem to engage in a real discussion around geoengineering at that level.

Governance is essentially nothing other than just having conversations amongst heads of state. I think we need to focus more conversation in the direction of geoengineering and have structured and thoughtful conversations around the finer details, like carbon capture on the one hand, and solar geoengineering on the other, and make decisions about which approaches to follow.

Aren’t the risks of using solar geoengineering ultimately just too high?

The biggest hesitancy around solar geoengineering has nothing to do with the physical risks. For the most part, it is all about about the risks of having solar geoengineering detract from the need to cut emissions in the first place.

That's what often comes under the heading of moral hazards. Here in the US, Newt Gingrich, the former speaker of the House of Representatives who is a very prominent Republican politician, once made a statement that we don't need to tax carbon, because hey, look, we've just discovered this new thing called solar geoengineering and we can solve the problem easily.

'I'm not trying to diminish this very real moral hazard that researching or even just discussing geoengineering would undermine the push to cut carbon emissions'

Now that is insane, and dangerous. No sensible person would make this argument. So, to be clear, I’m not trying to diminish this very real moral hazard that researching or even just discussing geoengineering would undermine the push to cut carbon emissions.

As for the risk of a rogue actor taking control of the climate, even if people do come to the conclusion that solar geoengineering is too much of a threat, if nations believe that it could be used irresponsibly or dangerously, then we could perhaps adopt some reverse psychology and use the threat of solar geoengineering as a reason to wake people up to the need to cut emissions in the first place. Now there’s a thought.