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Could Snowpiercer actually happen?
Not accidentally—there would need to be deliberate efforts over many generations to get an ice-covered Earth. But geoengineering to reduce the risks of climate change does pose other risks that are much more probable than the ones shown in Snowpiercer.
In the 2013 movie Snowpiercer, a train travels on a track around the world carrying all of humanity because the Earth has turned into a giant snowball. The cause? Scientists tried to use geoengineering, also known as climate engineering or climate intervention, to reverse global warming.
Geoengineering is defined as actions we take on purpose to change the Earth’s climate. This is different from current human-caused climate change, which is not happening on purpose: it’s a side effect of other activities, like using coal power to get energy. With geoengineering, humans would deliberately try to cool the Earth, to counter the accidental warming we’re causing today.
Snowpiercer shows one of the best-known geoengineering ideas, called “solar radiation management,” which involves changing how much sunlight the Earth reflects. The most frequently-proposed way to do this is by adding aerosols (fine particles or droplets suspended in gas) to the atmosphere. Dr. Douglas MacMartin, a climate engineering senior research associate at Cornell University, says, “that is the main idea in Snowpiercer. You could in principle fly up to the stratosphere and release aerosols such as sulfate, which would cool the planet.” These aerosols reflect the sun’s light back into space, leaving less sunlight to warm the Earth, and thus reducing some of the impacts of climate change.
On paper, if we sprayed enough aerosols in the stratosphere, they could reflect enough sunlight for the entire Earth to freeze over. From past episodes in the Earth’s history—so-called “Snowball Earth” periods—we know that an ice-covered Earth can reflect so much sunlight that the freezing temperatures would be stable for a long time.
But there’s a problem with this doomsday scenario. “The aerosols from geoengineering stay in the stratosphere for the order of a year or so, before they come down,” says MacMartin. “So if you want to actually use this to cool the climate, you have to be constantly replenishing the aerosols.”
And that means it’s very hard to “overshoot” with this kind of geoengineering, cooling the Earth more than we intend. MacMartin says, “That would basically be a very deliberate, sustained, collective effort, sustained over generations, to put vastly more into the stratosphere than you need to restore our climate.”
So Snowpiercer isn’t the effect we need to worry about. But there are real concerns that while geoengineering can help fend off global warming, it could also hurt our society in other ways. And this poses difficult tradeoffs for anyone weighing the risks of geoengineering against the risks of climate change. MacMartin says that sulfur seeding could change rain patterns, possibly affecting the ability of farmers to grow their crops. Aerosols in the atmosphere could also damage the ozone layer. If the aerosols are sulfates (as is usually proposed), the particles would eventually come down as acid rain, affecting vulnerable species.
In addition to environmental effects, “the things that worry me even more are the social dimensions, the human dimensions,” says MacMartin. “Who gets to decide? If there’s disagreement on that, does it lead to conflict?” Geoengineering is very different from fighting climate change by reducing greenhouse gas emissions, which requires global cooperation. If any one country—or even a corporation or wealthy individual—decided to begin geoengineering independently, their actions could affect the entire planet.
For all these reasons, MacMartin says that geoengineering should not be our first line of action in fighting climate change. But he adds that it deserves serious study. “Climate engineering is a serious subject, and while we haven’t done enough research yet to understand it, we are likely to face decisions about whether or not to use it in 15-20 years,” he says. “And those decisions shouldn’t be taken lightly, one way or the other… because the consequences of getting it wrong, either way, are severe. And if you don’t like the prospect of having to make that choice, the correct answer is to be way more aggressive on cutting our current greenhouse gas emissions.”