Shooting Reflective Aerosols Into the Stratosphere Won't Stop Global Warming

Caroline Delbert
Photo credit: AleksandarGeorgiev - Getty Images

From Popular Mechanics

  • Researchers from MIT have found that reflective aerosol clouds could deaden some global weather events.
  • Circulating global winds clear the air, literally—and stanching them has consequences.
  • Solar geoengineers speculate on ways to combat climate change using clouds and shields.

In what feels like a predictable turn, scientists say injecting the stratosphere with reflective aerosols would not help climate change enough to balance out the unwanted side effects. While the idea sounds outlandish, it’s a surprisingly old one, and it’s not the wildest thing ever suggested by a long way. Let’s take a closer look through the reflective fog.

The rationale for reflective aerosols is basically simple. “After all,” the Massachusetts Institute of Technology explains in a statement, “volcanoes do essentially the same thing, albeit in short, dramatic bursts: When a Vesuvius erupts, it blasts fine ash into the atmosphere, where the particles can linger as a kind of cloud cover, reflecting solar radiation back into space and temporarily cooling the planet.”

The collection of ideas inspired by volcanic ash and other reflective aerosol phenomena is gathered under the umbrella of solar geoengineering. Harvard University has a dedicated program to study it, with a big caveat: These ideas are meant to be “used in moderation” as part of a full portfolio of actions to try to reverse or stanch climate change.

In their new research, MIT scientists reveal how one specific kind of solar geoengineering could backfire. They ran simulations where the conditions were turned up to extreme levels in order to study the effects solar geoengineering would have on other aspects of the climate.

“The team considered an idealized scenario in which solar radiation was reflected enough to offset the warming that would occur if carbon dioxide were to quadruple in concentration,” MIT said in a statement.

The scientists discovered an amount of aerosol coverage required to offset that much more carbon dioxide would alter the storm tracks in both hemispheres and around the world. “The weakening of the storm tracks in the geoengineering scenario is partly related to a weakening of the pole-to-equator temperature gradient in both hemispheres,” the scientists write.

Their findings basically boil down to a globe with a more evened-out and level temperature, which may be good for reflection of solar radiation, but is harmful to the ebbs and flows that encourage circulation around the world. Stagnant air settles and dulls without the powerful and varying wind currents and storm systems that push it around. That means a pollution cloud that settles over Beijing or London stays there, like the smoke trapped in Comiskey Park on Disco Demolition Night.

Air travels in wild patterns around the entire globe, many in pretty predictable pathways like jet streams and trade winds. (You can see live global depictions of air currents like this one.) Ocean water circulates the same way, like ocean acidification sweeping into the Pacific Northwest and killing oyster larvae.

“Because of the way seawater circulates around the world, the deep water now washing ashore in Oregon and Washington is actually 30 to 50 years old and absorbed its CO₂ long before the fall of the Berlin Wall,” Yale Environment 360 explains.

It’s this “law of unintended consequences” that encourages researchers to run this kind of simulation to begin with. Yes, solar geoengineering sounds more like sci-fi than many other plans. But until we have experimental data in hand to show exactly what’s likely to happen and under what conditions, all the methods to reduce carbon dioxide or solar radiation remain in the realm of sci-fi. Examining the reality could turn up some surprising plausibilities.

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