The Washington PostDemocracy Dies in Darkness

Want to slow Arctic melting? Stop flying over the North Pole.

As the world keeps warming up, sea ice in the Arctic has been disintegrating rapidly. We've reached the point where scientists are now mostly just debating whether it will take a few years or a few decades before we start seeing ice-free summers up north.

So is that it? Is the Arctic doomed? Perhaps not just yet. A new study suggests one way that humans could slow the melting of the sea ice — by preventing international flights from crossing over the Arctic circle. These cross-polar flights are a surprisingly large source of black carbon pollution in the region. And if those planes diverted course, that could help fend off the day when the Arctic sea-ice collapses for good.

Commercial flights didn't start routinely traveling over the Arctic until 1998, when Russia finally gave other countries permission to use its airspace. Since then, these routes have become increasingly popular for air travel between Europe, North America and Asia. By 2010, some 50,000 flights a year were crossing the poles.

This has had a major impact on the Arctic. True, these cross-polar flights are just a small source of the greenhouse-gas emissions that are warming the planet. But they are a significant source of pollutants like black carbon, which absorb sunlight and warm the region. And pollutants from cross-polar flights tend to linger in the Arctic for a particularly long time, in part because the planes fly through the stratosphere, a relatively stable layer of the atmosphere. (Indeed, such pollutants could explain why Arctic ice is vanishing so much faster than scientists even expected.)

That's why, in a new paper (pdf) in Climatic Change, atmospheric scientist Mark Jacobson and his colleagues suggest that airlines could start diverting flights away from the Arctic Circle. Their modeling work suggests that if this happened, less black carbon would linger in the local atmosphere, the polar region would cool a bit (by about 0.015°C), and Arctic sea ice would even recover slightly in the next 22 years.

Here's an example of a diverted flight from Frankfurt to Anchorage:

Now, these diversions wouldn't be entirely cost-free. After all, airplanes currently fly over the Arctic because it's quicker. If all cross-polar flights had to be diverted, they would have to use more fuel. Not only would that cost about $99 million per year, but it would slightly increase the greenhouse-gas emissions that are warming the entire planet. The rest of the world would take a slight hit in order to slow down the drastic changes that are currently taking place in the Arctic.

That might be a trade-off worth making. After all, some scientists have suggested that the Arctic sea ice could disappear irrevocably once it reaches a tipping point (the exposed ocean water absorbs more sunlight than ice, which heats the region even further). And the collapse of sea ice could potentially have all sorts of dramatic effects, from speeding up global warming to boosting extreme weather in the United States and Europe. Slowing that process down could be prudent.

Still, rerouting flights is only a way of buying a bit of time — in the modeling work, the sea ice recovers slightly over the next 22 years, but it's not clear what happens after that. The world would still need to reduce greenhouse-gas emissions from all sources, including airplanes, if it wants to save the Arctic. Diverting flights is a small reprieve, not a lasting solution.

Further reading:

— Arctic sea ice hit a record low. Here's why it matters.

— When will the Arctic be ice free? Maybe four years. Or 40.

— A look at how a carbon fee for flights could reduce aviation emissions.