Scientists propose putting reflective aerosols into the stratosphere to reflect the sun's rays. But will this have unintended consequences?
What is Solar Geoengineering and Why is it Controversial?
Published: November 20, 2020
Frank Keutsch: Putting particles in the stratosphere could reflect back some sunlight to space, reducing the amount of sunlight that hits the surface and cooling down the planet..
Narrator: The effect would be immediate.
Steve Pacala: We know this works because every time a big volcano goes off and it injects aerosols into the stratosphere, the planet cools down.
Sheila Jasanoff: That's the idea behind solar geoengineering. It's like drawing a curtain over the face of the earth.
Frank Keutsch: The first time you hear about this and you think, “Well, that sounds like a really bad idea. How could that not go wrong?” But what we're doing to climate as humans, that really, to me, starts seeming also quite scary and crazy and really worrying.
David Keith: The fact is the CO2 is in the atmosphere. Without a time machine, we can't make it go away. We want to, in the long run, do carbon removal. But during the time that concentrations are high, we might want to do solar geoengineering to reduce the climate risk.
David Keith: All that is hard mounted to us.
Frank Keutsch: That is exactly what I was thinking.
David Keith: And then there is the balloon up there.
Narrator: Frank and David's team is designing a first-of-its-kind experiment called SCOPEX to investigate the impacts of solar geoengineering.
John Dykema: The only place I see that conversation getting sticky is where we do risk assessment on it.
Frank Keutsch: If you put these particles out, what happens when these come back down? What happens when it gets into the environment? Are we endangering people?
David Keith: There are lots of things that we might need to know where the existing experimental background is bad. You actually have to go out and make measurements.
Narrator: The plan is to launch a 100 foot balloon into the stratosphere and release a plume of reflective aerosols.
Frank Keutsch: We want to put out the particles of calcium carbonate, for example, and then go back through this plume and see whether the evolution of the air is the way we predicted based on our laboratory results.
Frank Keutsch: This is an experiment on a very small scale. And in fact, the amount of material we’re putting out is less than a normal airplane flight puts out.
Narrator: SCOPEX may be small, but many fear a large-scale manipulation of Earth’s atmosphere could trigger a cascade of dangerous, unintended consequences that ripple across the planet.
Sheila Jasanoff: Nothing in our scientific capability actually enables us to understand the complexity of the interactions that would be set loose.
Jane Long: It’s not just that it lowers the temperature, but what are some of the other effects on the hydrologic cycle, or on heat waves and droughts?
Sheila Jasanoff: This is a manipulation of the Earth’s atmosphere on a huge scale. What happens if things go wrong?
Narrator: SCOPEX is designed to start answering those questions. But there may be effects, beyond the physical, that no experiment can predict.
Sheila Jasanoff: If we think that there's this solution out there then people may think it doesn't matter if you're polluting the planet.
David Keith: The root of the concern is that solar geoengineering research, however well-intentioned, will be used as an excuse for big fossil fuels to fight emissions cuts.
Scott Denning: It's just like a sci-fi dystopian novel or something where we continue to just belch all this CO2 into the atmosphere, but, “Hey, it's OK because we've got these little umbrellas that are, you know, hiding us from the sun.”
David Keith: Solar geoengineering does not get us out of the ethical and physical requirement to cut emissions.
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