Most of the worry over greenhouse gases centers on carbon dioxide, and rightly so: thanks mostly to the burning of fossil fuels, levels of this heat-trapping pollutant have soared to nearly 400 parts per million in the atmosphere, far above the 270 ppm that prevailed before 1800 or so, and they’re still rising — triggering a rise in sea level, temperature, and other telltale signs of climate change.
But CO2 isn’t the only greenhouse gas: methane traps heat too, and it’s a lot more powerful, molecule for molecule, than carbon dioxide. The good news is that there’s much less methane up there than CO2. The bad news: global warming could release vast natural deposits of methane trapped in the Arctic, making the temperature increase we’re already seeing go into overdrive.
No one knows if and when that might happen, but even the mere possibility has galvanized scientists into pondering what they could possibly do about it should the worst come to pass — and a paper in Environmental Science & Technology is the latest and most comprehensive assault on the problem yet.
Methane-induced melt-hole on a frozen lake in the Brooks Range in Alaska. Credit: Katey Walter Anthony.
In a worst-case scenario, suggest Joshuah Stolaroff, Lawrence Livermore National Laboratory, and his co-authors, with huge plumes of methane erupting into the atmosphere from underground, scientists might have to battle the gas with bombs, and more. “If the concentration of methane is high enough . . . ” they write, “. . . then a laser can be used as a remote ignition source.”
This worst-case scenario is by no means certain, but it’s certainly plausible. Scientists know that enormous reserves of methane — rivaling the world’s known reserves of fossil fuels — are buried in the permafrost and along the continental shelf surrounding the Arctic Ocean, trapped in ice formations known as methane hydrates. If the water warms enough, the gas could escape relatively quickly to add it’s planet-warming power to the greenhouse gases that are already there. This is probably what happened during a rapid warming episode known as the Paleocene-Eocene Thermal Maximum, about 55 million years ago. The temperature shot up by about 11° F at the time, causing mass extinctions of species, among other effects.
No one knows how long it took for the methane to escape back then, nor how long it might take if it happened again. But if the release were relatively slow — an event stretching over 1,000 years or more — it would make global warming harder to deal with. A slow release would obviously be easier to deal with, Stolaroff said, especially if it emerged in concentrated pockets. “If it came out of particular hotspots,” he said, “like specific Arctic lakes, you could imagine deploying some technological solution at the site, which might involve flaring the gas, or collecting it for energy.”
On the other hand, if it came out uniformly over a large area — even slowly — the challenge would be a lot greater. “It’s hard to imagine putting a tarp down over millions of square kilometers,” Stolaroff said. One option might be to resort to geoengineering — abandoning the idea of suppressing the methane directly and choosing instead to reflect some of the sunlight reaching the Arctic back into space. “You could whiten the ocean by creating microbubbles,” he said, “or put particles into the atmosphere to shade the surface.” Or you might try and seed the atmosphere with some sort of methane-eating substance.
And if the release were sudden and widespread — the worst of the worst case? “I don't know what the response might look like, but it would be massive,” he said. Laser ignition is one possibility, and, write the authors, “incendiary ballistics” — that is, explosive-laden missiles — “may be another route.” Any possibility mentioned in the paper, said, Stolaroff, “is a possibility. Just on a much larger scale, and more rapid.”
A methane apocalypse isn’t the entire focus of the new paper, although it’s admittedly the most dramatic. But humans are putting the stuff into the atmosphere at a growing rate even without natural eruptions in the Arctic: methane comes out of rotting garbage in landfills, rotting manure in animal feedlots, food digesting in cows’ stomachs. It’s a waste gas that escapes from oil and natural gas wells and oil refineries — and that’s just a partial list.
In many of these situations, Stolaroff said, it’s easy enough to deal with the problem. “If the source is confined [a well or a landfill, for example], or if it can be confined [a cattle barn], you can simply burn it.”
Burning converts methane into CO2, but since methane is some 25 times more effective than carbon dioxide at trapping heat, that’s a good thing. “Burning,” he said, “reduces the global-warming impact by 90 percent.”
The paper outlines strategies for dealing with unconfined methane sources as well. Ranchers can deal with methane-laden burps from grazing cattle through changes in feed; rice farmers can cut down on the methane bubbling up from rice paddies by draining them of water every so often. And the list goes on.
Stolaroff emphasized that the new study shouldn’t be taken as final or definitive. Just the opposite, in fact. “Our goal,” he said, “was to get people thinking about this. We wanted to lay out the options, then let each researcher figure out what aspect of the problem they might want to study. We believe that the consequences of a large-scale release are so dire that we need to start planning for it immediately.”