The planet is in rough shape due to rising carbon emissions, and the worldâ€™s governments donâ€™t seem to be in any hurry to change course. That has us on a collision course with dramatic climate change, and that has at least some scientists looking at a dramatic, last resort: dimming the sun to cool the Earth.
Researchers have a vision for sending a bunch of planes or balloons into the atmosphere to spray particles high in the sky, a process known as stratospheric aerosol injection. Those particles would reflect some sunlight back into space, meaning thereâ€™s less incoming energy to be trapped by greenhouse gases and warm the Earth.
Scientistsâ€™ proof of concept for this scheme are volcanic eruptions, which also send reflective particles high into the atmosphere. Eruptions have cooled Earth in the past, and a manmade version could do the same in the future if the planet gets too hot. Some studies show we could do this with a $US100 ($144) billion dollar investment.
Compare that to multi-trillion dollar plans, and it could look like a bargain.
But stratospheric aerosol injection can be dangerous. Sure the Earth would cool down (good), but blocking the sun could change weather patterns and ocean currents in weird and not wholly predictable ways (bad). Indeed, when Mount Tambora, a volcano in Indonesia, erupted in 1815, it blocked so much sunlight that average global temperatures dropped by almost 2 degrees Fahrenheit (3.6 degrees Celsius). The following summer saw widespread famine and crop loss.
Thereâ€™s also a catch-22. Undertaking stratospheric aerosol injection could be dangerous, but so could stopping the process once weâ€™ve started. Some research has shown that once we start spraying particles to block the sun, we might be locked in for life. Thatâ€™s because if we stopped spraying particles, the Earth might suddenly get warmer over just a few years, giving all the planetâ€™s life no time to adapt.
So yeah, scary. But scientists and policymakers are considering it more and more the closer the planet gets to overshooting levels of heating outlined in the Paris Agreement. Bill Gates is funding research into it, and presidential candidates (well, Andrew Yang) have included projects to cool the globe in their climate plans.
At least some scientists think stratospheric aerosol injection could be used in tandem with plans to phase out of fossil fuels since the impacts of carbon pollution can last centuries. Which, ok, I get it.