Thoughts Sparked by Snowpiercer: CW-7 & SO2

Last weekend I saw Snowpiercer. Briefly put, I found it was clever, suspenseful and inventive. It also marks another step towards geoengineering entering the popular consciousness. It begins with planes spreading something called CW-7 into the atmosphere as a means of cooling it, but a miscalculation which ends up plunging the world into an ice age. The mechanics of this aren’t important for the film’s story—they only needed some way for the Earth to get cold—but it’s nice to see intentional tinkering with climate treated as not only dangerous, but potentially more dangerous than our unintentional footprint.

Geoengineering is often treated as some kind of easy way out of climate change. Just find some way to make the Earth’s surface more reflective—distributing sulfate particles in the stratosphere seems to be the most popular choice (simulating the cooling that comes from volcanic eruptions)—and bam! More light is reflected into space and your warming problem is solved. One of the early proponents of sulfate-based geoengineering, Ken Caldeira, suggested beginning with localized sulfate distribution in the Arctic. It’s unpopulated and if geoengineering manages to cool the area enough ice cover would regrow, reflecting more light and amplifying the cooling. Piece of cake?

Alas, c’est pas de la tarte. Distributing sulfare particles in the atmosphere, at least at levels discussed in geoengineering circles, won’t cause another ice age along the lines of Snowpiercer (CW-7 seems to have more in common with Kurt Vonnegut’s fictional ice-nine than SO2), but it would would other side effects. Blocking sunlight suppresses evaporation, even if just limited to the Arctic. Looking at volcanic eruptions’ effect on the climate system, Alan Robock, Luke Oman and Georgiy Stenchikov hypothesized that stratospheric sulfate injections would likely suppress African and Asian monsoon cycles with bring rain to crops in Africa and South Asia. There’s not much point in cooling off the planet if you’re going to jeopardize billions of people’s food source in the process.

The big danger in aerosol-based geoengineering comes not from overshooting a temperature target, but from single-mindedly concentrating on temperature. When it comes to assessing the economic repercussions of climate change, temperature is a good proxy for economic damage—the warmer the costlier. Despite concerns about how climate change will change natural environments, it’s the human and economic costs that really worry people. Actually going forward with geoengineering would be an economic choice, something less expensive continued warming. Geoengineering schemes must not be judged by how much it cools the planet, but by how much it benefits us.

 
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