Wired: Shall we notice it? Visually, do we see anything?
KR: Yes, on an absolute scale. It changes the ratio of direct and diffused radiation. So the idea is that the sky will become a little whiter on average and the sunsets, for example, will become more vibrant. This is of course much smaller than the difference between going to town from the California desert. The white sky thing, too, is probably not the biggest problem, in my opinion.
Wired: What about any concerns about toxicology? Is this thing majestic for living creatures on earth?
KR: It’s not majestic — it’s the same thing that comes from a power plant. Its large concentration in an area makes people and crops sick. But, in terms of scale, the amount you need in the stratosphere is much smaller than what we emit from a power plant, and it spreads across the planet.
People have done some research on this, and it seems that perhaps the biggest risk from particles would be the selection of sensitive high-latitude ecosystems – so polar ecosystems that do not currently get much exposure to urban pollution, but need to get more out of it. Especially because the particles move towards the poles, usually, before they leave the stratosphere.
Wired: Say a country unilaterally says, ‘We’re going to do it.’ They want to cool their own country by spraying the stratosphere, and it doesn’t matter if it’s going to wrap around the planet.
KR: Legally, it’s complicated, because countries basically own their airspace up to space. It’s a little vague. So people can spray things in their country and it can go everywhere. And then [the particles] Stay in the atmosphere for about a year and a half on average. They spread and the radioactive effect is effective immediately. This is why after a large volcanic eruption, you immediately see a drop in global temperature that lasts about one to two years and then goes down again. So you don’t have to spray stuff every day, necessarily. If you stop doing this for two years, the effect will go away.
I’m having a hard time seeing how we are No. I’m going to do it at this point, in fact, because it’s so cheap. Already the effects of climate change are being seen to be so disruptive that I cannot see in this world how such a low-cost solution is not implemented by anyone. There is nothing on Earth that can quickly cool the planet. Even if we start rapidly decarbonizing and removing CO2 from the atmosphere, it is still a decade scale for the consequences. When exposed to sunlight, the climate response begins immediately.
Wired: I have seen some modeling that if you suddenly stop solar geoengineering, you will have problems with temperature. Dramatically climbing and damaging species.
KR: If the program is interrupted, and we block a lot of warming with stratospheric geoengineering, you will get warmed up really fast if someone stops doing it. I mean, it would be catastrophic if we stopped treating our drinking water, wouldn’t it? There are some things that people do that we have to do, or it is catastrophic.