Mr. Wagner, we speak to each other in the video call. Looking out the window of your office at Columbia Business School, what color is the sky over New York right now?
Blue with white clouds. And yes, that’s what it will look like if we do solar geoengineering.
So if we put lots of sulfur dioxide into the atmosphere to create a kind of aerosol screen that dims the sun’s radiation. The aim is to slow down the ongoing global warming caused by the climate crisis. Some scientists fear that if we did, we would be living under white skies in the future, along with various other nasty consequences.
I don’t think we could see the aftermath with the naked eye. Perhaps sunsets would become redder, like air pollution in cities like London during the Industrial Revolution. There are enough dangers in solar geoengineering. That the sky won’t be blue anymore isn’t one I worry about.
Solar geoengineering would mean that we deliberately pollute the air again with sulfur dioxide, including side effects that we cannot yet estimate. One concern, for example, is that the monsoon could be completely absent due to the change in solar radiation. Isn’t this a technology that would lead us straight into the collapse of the global climate and ecosystem?
Aren’t we now counteracting this collapse of the global climate and ecosystem? So yes, the question is indeed: what are the risks of solar geoengineering and how do they compare to the risks of the climate crisis? With the monsoon, too, the question is whether the current climate crisis is having a much greater impact.
Clearly, solar geoengineering is not the solution, it cannot be. We must reduce CO₂ and other greenhouse gases. Then we have to adapt better to climate change. And we now also have to use technology to get CO₂ out of the air again. Our situation is so muddled that we really need every straw. So I think it is necessary to at least do more research on solar geoengineering to understand more about it. Because today we cannot say conclusively whether it could be part of the solution or whether it should not be part of the solution under any circumstances.
In 2017 you co-founded the first research program on solar geoengineering at Harvard. When did you first hear about solar geoengineering and think, ‘Oh, I should take that seriously’?
I’ve been interested in climate change since I was 12 years old, I first heard about solar geoengineering in the late 90’s, around 18 or 19. My first reaction was: Okay, that sounds crazy. Then I ignored the topic for ten years and worked on other topics as a climate economist. For most scientists, this was a kind of taboo subject anyway because of the potential risks. But after atmospheric chemist and Nobel Prize winner Paul Crutzen called for more research in 2006, the taboo was broken. That’s when I started researching it.
They believe that it is only a question of when, not if the technology will be used. Why?
Because unchecked climate change has already progressed so incredibly far. So I believe it’s a matter of time before someone, somewhere, actually tries to do solar geoengineering on a large scale. The first attempts on a small scale have already been made.
Are you talking about the American tech start-up Make Sunsets? The company sells so-called “cooling certificates” and then allegedly sends balloons full of sulfur dioxide into the sky, which are supposed to burst at an altitude of about 20 kilometers.
These are, with all due respect, some crazy people. That’s a big step in the wrong direction for what this company wants to do with private money. But yes, there is that too. However, I was thinking of a research project in England, where last September scientists sent a balloon containing 400 grams of sulfur dioxide into the stratosphere at an altitude of about 30 kilometers for testing purposes. They call the program SATAN, by the way.
Doesn’t sound very reassuring.
Thank god that doesn’t sound reassuring. The real issue is that we need to reduce CO2 emissions, and solar geoengineering is not a solution to this CO2 problem. It’s more of a painkiller for an overweight 75-year-old who has been eating too much fat and not exercising enough for far too long and now with massive heart problems can’t just start jogging.
When Mount Pinatubo erupted in the Philippines in 1991, the volcano ejected megatons of sulfur aerosols into the atmosphere. This dimmed the solar radiation so much that in 1992 the average earth temperature actually dropped by 0.5 degrees. When the particles settled, the temperature shot up again. How would we humans lower the earth’s temperature?
One would actually try to partially imitate the consequences of such a volcanic eruption. This would require new, high-flying aircraft with a massive fuselage and a very large wingspan. These machines could transport the sulfur dioxide into the stratosphere and then deploy it at an altitude of 20 kilometers near the equator. That would be perhaps the best variant in quotation marks. However, these aircraft do not currently exist.
Why would the sulfur particles have to be released at the level of the equator?
The goal would be to lower the global average temperature and not trigger any regional effects. The latter could result in potentially catastrophic weather phenomena. Due to the atmospheric circulation from the equator to the polar caps and then from west to east, a global effect would most likely occur when deployed there.
In theory, a single state that has the technical capacity and the money to do so could go it alone.
Gernot Wagner, climate economist on solar geoengineering.
Who can make such global decisions and according to what criteria?
In fact, there is no global, democratically legitimate institution for this, at least not the United Nations. The problem is that the technical implementation of solar geoengineering would be relatively easy. So theoretically, a single state that has the technical capacity and the money to do it could get started on its own. I would say there are a dozen worldwide.
Bill Gates helped fund your earlier research project at Harvard. Mache suspect financial interests behind it and not a commitment to climate protection.
Bill Gates was one of the sponsors of our research program. But it wasn’t about developing patents or anything like that at all. Gates, self-aware of the public reception his involvement might have, has insisted he isn’t the sole sponsor. For example, he gave four out of a budget of ten million dollars. And as far as I know, he invests billions in research to reduce carbon emissions. That’s the right ratio in general, I think. We should invest in solar geoengineering research, but invest a thousand times more in actual climate research, climate policy and reducing CO2 emissions.
Republican Newt Gingrich, on the other hand, declared climate protection measures superfluous years ago because solar geoengineering could stop global warming. Aren’t the driving forces behind this research simply those who want to continue burning fossil fuels for as long as possible?
Yes, that’s a huge problem, the so-called moral hazard. There is a great danger that someone who is benefiting very, very much from the situation today and reading this will think, ‘Thank God this technology exists, it will save us. I can keep driving the SUV down the highway, don’t have to replace the gas stove, don’t need a heat pump and don’t have to change my life at all’. That would be completely wrong.
That would be like suggesting that the 75-year-old obese man go on smoking because there is chemotherapy. This is perhaps an even better analogy for solar geoengineering. So, yes, there is that moral hazard. But maybe there is also the opposite, and someone reads this interview and thinks, this Frankenstein method is a step too far for me, I’d rather step off the gas pedal.
So what do you suggest?
I am promoting a dedicated moratorium against the use of solar geoengineering combined with an explicit permit for small-scale exploration. And when I say small, then it’s about the emission of these 400 grams of sulfur dioxide in the stratosphere. Even the local influence is zero. There is a greater risk that part of the balloon will fall on someone’s head.
And it is better that we research this technology now, instead of blindly slipping into a situation in which a single actor says after the third century cyclone with hundreds of thousands of deaths within three years: Well, now there is no other way, now let’s do it das. And we learn more about whether and how technology can possibly help us after all. However, the decision about their use must not lie with the scientists. Of course, that has to be a political decision.
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