Holy sun-repellant spray, Batman! Could injecting billions of kilograms of sunlight-dimming aerosols into the atmosphere save the planet from industrial climate destruction? Or is that just Joker-level insanity? A new Columbia Climate School report definitely suggests that caution is warranted.
Stratospheric aerosol injection (SAI) is essentially a “non-nuclear winter” in which an intentionally deployed atmospheric shroud would block sunlight from heating the earth, allowing industrial pollution to continue as usual. But why would anyone consider such a risky, dramatic climate plan at all, especially one previously dismissed as science fictional?
Because, as a previous report by the Inter-Governmental Panel on Climate Change states, industrial climate change is causing wide, “rapid changes in the atmosphere, ocean, cryosphere [ice zones], and biosphere” that are altering “weather and climate extremes in every region across the globe.” The result is “adverse impacts and related losses and damages to nature and people.”
But what about all our recycling, car-pooling, biking, hiking, and gardening? Aren’t we in the end-game of stopping an eco-killing Thanos from snapping his fingers and our snapping our biosphere’s neck?
Not even close. Greenhouse gas emissions aren’t slowing – they’re actually increasing. As the International Energy Agency reported in 2024, carbon emissions from the energy sector reached a new record as total “energy-related CO2 emissions increased by 0.8% ... hitting an all-time high of 37.8 Gt CO2.”
And according to the Royal Meteorological Society, in 2024, for the first time, the world exceeded the 1.5 °C threshold for an entire year (in fact, it was 1.6 °C above pre-industrial levels). Keeping global temperate to no more than a 2 °C increase above pre-industrial levels, according to the Paris Agreement, stands between life as we know it and a cascading climate system failure that humans won’t be able to stop.
Perhaps most unjust is the fact that populations who’ve done the least to cause climate chaos face some of the greatest damage from it, as when rising sea levels swallowed eight Micronesian islands in 2017, with Tuval, Kiribati, the Maldives and the Marshall Islands facing "stronger storms, freshwater shortages, and damaged infrastructure" before potentially disappearing underwater.
So, in the face of unthinkable destruction, previously unthinkable proposals have now achieved thinkability. In 2018, we reported on a proposed 15-year SAI plan to inject sulphates into the atmosphere about 20 km (12 mi) above ground, costing around US$2.25B annually.
Such a plan would require designing entirely new airplanes for payload delivery and require around 4,000 flights in its first year. Another SAI variation specifically targets the Earth’s frigid polar regions, refreezing them because they’re warming more quickly than the rest of the planet and also causing sea levels to rise.
What are the risks of SAI?
But what if SAI doesn’t work, and climate disruption keeps getting worse? Can we just take out whatever gases we put into the atmosphere? Well, no. SAI isn’t the same as building a fence we can just tear down if we don’t like. Removing gases and particles from the air is more like trying to take the chocolate out of a cake that’s already baked because you want vanilla.
But what’s far worse is that deploying SAI could be catastrophic, meaning we’d be facing both climate chaos and whatever monsters we’ve unleashed. That brings us to the new Columbia Climate School report by Miranda Hack, V. Faye McNeill, Dan Steigart and Gernot Wagner, published in Nature in October 2025.
The scientists state, “Without international cooperation, SAI could do more harm than good. Unilateral or poorly planned deployment could worsen droughts, disrupt monsoons, or shift storm patterns.” Just as the eruption of Mt. Pinatubo “disrupted the Indian monsoon system, leading to decreased rainfall across South Asia, and caused warming in the stratosphere and depletion of the ozone layer,” SAI could cause “acid rain and soil pollution.”
That’s because when high-altitude clouds of sulfur dioxide eventually form sulfuric acid, the resulting acid rain will help destroy the forests, jungles, crops, tigers, penguins, and reindeer that SAI was supposed to protect.
The authors of the report also caution policy makers that most “SAI modeling literature focuses on optimal deployment scenarios, in which practical constraints – microphysical, geopolitical, and economic – are not considered.”
In other words, SAI assumes that all governments and corporations will cooperate nicely, which can happen, as with the 1987 Montreal Protocol and its amendments to save the ozone layer by phasing out chlorofluorocarbons. But as Earth.org chillingly and succinctly reports, “environmental treaties consistently fail.”
Furthermore, according to Hack and her colleagues, cost and supply of SAI materials such as diamonds and zirconia, governance, and other factors are substantial risks for SAI success, with one of the biggest risks being the difficulty of “dispersing solid aerosols at scale in the desired size range,” as well as what all the “potentially formed aggregates” will do when they fall to Earth. That being said, “Solid mineral candidates have been proposed as a sulfate alternative, potentially lowering environmental risks like ozone depletion and absorption of radiation.”
The stakes of climate chaos and potential solutions are enormous for humanity and all our co-denizens of Planet Earth. It’s clear that our current course is catastrophic, and while SAI could work, if it fails and causes chaos that combines with climate disaster, our odyssey as a species may come to a violent, miserable end. So, what if, instead, governments focused on simply reducing greenhouse gases?
If only someone had thought of that plan decades ago.
Source: Columbia Climate School
