How long do you think it’ll be before we’re able to bend the weather to our will? A massive rainmaking program in China, efforts to seed new oases in the Arabian peninsula, or chemically induce snow for skiers in Colorado. 100 years? 50 years? 20? Those who know how to write a teaser hook for a podcast episode will have correctly guessed that all these things are already happening today. And the techniques being used could be turned to managing climate change as well. Today’s guest, Kelly Wanser, founded SilverLining — a nonprofit organization that advocates research into climate interventions, such as seeding or brightening clouds, to ensure that we maintain a safe climate. Links to learn more, summary and full transcript. Kelly says that current climate projections, even if we do everything right from here on out, imply that two degrees of global warming are now unavoidable. And the same scientists who made those projections fear the flow-through effect that warming could have. Since our best case scenario may already be too dangerous, SilverLining focuses on ways that we could intervene quickly in the climate if things get especially grim — their research serving as a kind of insurance policy. After considering everything from mirrors in space, to shiny objects on the ocean, to materials on the Arctic, their scientists concluded that the most promising approach was leveraging one of the ways that the Earth already regulates its temperature — the reflection of sunlight off particles and clouds in the atmosphere. Cloud brightening is a climate control approach that uses the spraying of a fine mist of sea water into clouds to make them 'whiter' so they reflect even more sunlight back into space. These ‘streaks’ in clouds are already created by ships because the particulates from their diesel engines inadvertently make clouds a bit brighter. Kelly says that scientists estimate that we're already lowering the global temperature this way by 0.5–1.1ºC, without even intending to. While fossil fuel particulates are terrible for human health, they think we could replicate this effect by simply spraying sea water up into clouds. But so far there hasn't been funding to measure how much temperature change you get for a given amount of spray. And we won't want to dive into these methods head first because the atmosphere is a complex system we can't yet properly model, and there are many things to check first. For instance, chemicals that reflect light from the upper atmosphere might totally change wind patterns in the stratosphere. Or they might not — for all the discussion of global warming the climate is surprisingly understudied. The public tends to be skeptical of climate interventions, otherwise known as geoengineering, so in this episode we cover a range of possible objections, such as: • It being riskier than doing nothing • That it will inevitably be dangerously political • And the risk of the 'double catastrophe', where a pandemic stops our climate interventions and temperatures sky-rocket at the worst time. Kelly and Rob also talk about: • The many climate interventions that are already happening • The most promising ideas in the field • And whether people would be more accepting if we found ways to intervene that had nothing to do with making the world a better place.Chapters:• Rob’s intro (00:00:00)• The interview begins (00:01:37)• Existing climate interventions (00:06:44)• Most promising ideas (00:16:23)• Doing good by accident (00:28:39)• Objections to this approach (00:31:16)• How much could countries do individually? (00:47:19)• Government funding (00:50:08)• Is global coordination possible? (00:53:01)• Malicious use (00:57:07)• Careers and SilverLining (01:04:03)• Rob’s outro (01:23:34) Producer: Keiran Harris. Audio mastering: Ben Cordell. Transcriptions: Sofia Davis-Fogel.

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