Engineering the Climate: Can Injecting Chemicals in the Sky Help Save the Planet? (Professor David Keith)

**Gabriel Gatehouse** (0:08)
Hello, and welcome to Radical, conversations about the global forces reshaping our world and the radical ideas that could define the future. I'm Gabriel Gatehouse, I'm with you this week, and we're going to look at a very radical proposal to an extremely intractable problem. The world is getting hotter. To stop it, we need to reduce our carbon emissions, but we're manifestly failing to do so.
Now, this is not a perfect analogy, I know, but if you think about the human global population as a kind of single body, I think we're a bit like an alcoholic, right? We're in trouble.
We know we're in trouble and we know what we need to do to turn it around. We keep going to AA meetings or maybe UN climate conferences, where we make plans to cut down on our drinking or burning fossil fuels. But as soon as we leave the meeting, we fall straight back off the wagon. So some people are proposing a different solution, and we're going to leave the AA analogy behind here. It's called geoengineering. It's the deliberate large scale manipulation of Earth's climate systems to counteract human-made climate change.
Now, some of these ideas, to me at least, sound like something a Bond villain might dream up. I mean, researchers are looking at ways to dim the sun by replicating the effect of volcanic eruptions, or brightening clouds to reflect more sunlight back into space. And some are even talking about putting mirrors into space. It's controversial, it is radical, and the stakes are high. I mean, it's an idea that could either save the world or hasten its end, depending on your point of view. So is this madness? Is it a dangerous and arrogant attempt to control the forces of nature, forces that we don't even properly understand? Is it a distraction from what we know we need to do with potentially catastrophic side effects, an ethical minefield and a geopolitical nightmare all rolled into one? Or is it an essential tool in our arsenal? Maybe our best, our only realistic solution to the scale and the urgency of the climate crisis.
These ideas are not actually new. For decades, they've been on the fringes. But now, as the effects of climate change are becoming more urgent and more visible and more severe, these kinds of radical interventions are increasingly being talked about as serious propositions. My guest this week is Professor David Keith from the University of Chicago. He's one of the most visible researchers in this space. He's a radical individual in a radical field. And when it comes to solar geoengineering, dimming the sun, there are scientists who talk about doing more research, feasibility studies. But Professor Keith says it's time to start doing it. Remember that if you subscribe to this podcast on BBC Sounds, you won't miss future episodes, including Your Radical Questions, which is our Q&A episode that comes out on a Monday. But now, to Professor David Keith.
Professor David Keith, welcome to Radical.

**David Keith** (3:26)
Hello there. Happy to be here.

**Gabriel Gatehouse** (3:28)
David, could we just start off by defining geoengineering? What is it?

**David Keith** (3:35)
Geoengineering is the idea that humans could deliberately intervene somehow on the earth system to reduce the harms from carbon dioxide emissions that are causing climate change. And broadly, there's two ways to do this. One is to reduce carbon dioxide by taking carbon dioxide out of the atmosphere to remove carbon dioxide.
And the second idea is to make the earth a little bit more reflective or maintain the reflectivity it has by various ways that say make clouds brighter or scatter some sunlight back that would reduce the energy imbalance caused by accumulated greenhouse gases, the energy imbalance that is causing climate change. OK.

**Gabriel Gatehouse** (4:15)
And the first bit of that, removing carbon from the atmosphere, we're already doing that, right?

**David Keith** (4:21)
Not at a serious scale. There are lots of tiny ways that we're doing it. Nature does it.

**Gabriel Gatehouse** (4:27)
But we have experiments that are looking at creating different sorts of plant life and getting them to sink to the bottom of the ocean. Those kinds of experiments are ongoing, are they?

**David Keith** (4:37)
Well, it's beyond experiments. And what you said is a little ridiculous, actually. I'd say the large scale ways that are practical to do this are mostly kind of copying what nature does. So the long-term thing that nature will do to remove the carbon dioxide is reacting with rocks. So as some of you may recall from high school, CO2 is a weak acid and acid and bases react to make salts. And if humans just disappear from the planet, that's what would happen. CO2 is this weak acid, carbonic acid in water that reacts with rocks that are bases.