The Best Way to Find Out if We Can Cool the Planet

A few years ago, the idea of deliberately blocking the sun to combat climate change was taboo for scientists. But a lot can change in a short time.

As the disastrous effects of climate change mount, Congress has asked federal scientists for a research plan, private money is flowing and rogue start-ups are attempting experiments — all signs that momentum around solar geoengineering is building fast. The most discussed approach involves spraying tiny particles into the stratosphere to reflect sunlight and cool the planet. Other proposals include injecting sea salt into clouds to increase their reflectivity or using giant space parasols to block the sun.

It might all sound like dystopian science fiction, but some techno-futurists, like OpenAI’s chief executive, Sam Altman, are already normalizing it: “We’re going to have to do something dramatic with climate like geoengineering as a Band-Aid, as a stop gap,” he said in January at the World Economic Forum in Davos.

No one fully understands the risks of these technologies — which could include calamitous disruptions in weather — or how significant the benefits could be. I’m increasingly convinced that we should do more research on solar geoengineering. But such high-stakes science requires extraordinary levels of transparency and accountability to the global public. The alternative is clandestine research controlled by corporations or autocratic regimes, lurching toward deployment without knowing — or knowing and not sharing — the true risks.

The potential risks of solar geoengineering are serious. Spraying reflective particles in one place, for example, could significantly change rainfall patterns elsewhere. What’s more, once anyone starts solar geoengineering at a larger scale, suddenly stopping it could lead to “termination shock” — global temperatures rapidly readjusting to where they would have been without geoengineering. With such terrifying points of no return, every accelerating step of research requires global public participation and deliberation.

Most research so far has been tentative and contained to computer simulations. But to know what will happen in the real world, we also need outdoor experiments. By launching an instrument-laden balloon into the stratosphere, for example, researchers could release a tiny amount of particles and measure how they interact with the atmosphere, with minimal environmental risk.