ve long felt that one of my great failings as a climate communicator has come in trying to get across the dangers posed by methane, the second most damaging greenhouse gas, after carbon dioxide. Despite long years of many people trying to underscore the risks of methane, our go-to shorthand for climate pollution remains “carbon.” That’s why companies and political leaders boast about how much they’ve reduced their carbon emissions, but, if they managed the trick by substituting gas for coal, their total contribution to global warming has barely budged—because natural gas is another word for methane, and because when it invariably leaks from frack wells and pipelines it traps heat, molecule for molecule, much more effectively than CO2.
Now, finally, methane appears to be having its day in the sun. A key thing to understand about methane (CH4) is that it doesn’t hang around in the atmosphere anywhere near as long as CO2: its life span is measured in decades, not centuries. While methane is in the air, it traps a lot of heat, but a dramatic reduction in the amount of CH4 would be a quick fix that would help slow the rise of global temperatures, giving us more time to work on the carbon quandary. As Stanford University’s Rob Jackson told me, last week, the best estimate is that methane caused about a third of the global warming we’ve seen in the past decade, not far behind the contributions of CO2.
The first way to reduce methane in the atmosphere, of course, is to stop building anything new that’s connected to gas: stop installing gas cooktops and gas furnaces, and substitute electrical appliances. And stop building new gas-fired power plants, instead substituting sun, wind, and battery power. And, as a really important new study by the star energy academics Bob Howarth and Mark Jacobson emphasizes, by all means do not start using natural gas to produce hydrogen, even if you’re capturing the carbon emissions from the process. This so-called “blue hydrogen,” beloved by oil and gas companies, and included in the bipartisan infrastructure bill, does not cut global-warming emissions, in large part because of the methane that vents out in the process. If we have to live with some natural gas for a while (and there are an awful lot of furnaces that will take years to switch out), then we should reduce leaks as best we can—a process made infinitely harder by the Trump Administration’s decision to stop monitoring the problem at all.
But methane doesn’t just—or even mostly—come from fossil fuels. It’s also emitted by cattle, by rice production, and, naturally, from wetlands. Our actions are making these sources bigger—we’re raising more cattle, for instance, and, as temperatures rise, marshes give off more of the gas. Scientists continue to fear that truly huge increases in methane could come from a warming Arctic, both from thawing permafrost and from underwater methane clathrates, or methane ice formations, which are likely to melt as temperatures rise. (Russian researchers continue to find clues that such releases may be beginning, but so far the spike in methane seems to be coming from other sources.)
Given both the threat and the opportunity, some scientists have begun wondering whether there might be ways to scrub some methane from the atmosphere. As with carbon dioxide, you can remove CH4 with “direct air capture,” which uses machines that filter the atmosphere to remove the molecules. But, as with CO2, this is, for the moment anyway, too expensive to do at scale. So a group of scientists at the California nonprofit Methane Action is looking at ways to catalyze reactions in the atmosphere that could transform the methane, and they think they may have found a method that makes use of ship smokestacks. Daphne Wysham, a veteran environmentalist and the group’s C.E.O., explains, “Many ships now burn bunker fuels that contain iron. While bunker fuels are terribly polluting, one positive aspect of the combustion of bunker fuels with iron is that they may be inadvertently enhancing one of two natural ‘sinks’ for methane—the chlorine atom. Our scientists hypothesize that, when bunker fuel is burned, iron particles end up in the smokestack of the ship, and that the mix of iron, sunshine, and salt-sea spray is generating a mixture of iron trichloride and chlorine atoms, which may be oxidizing methane in the ship’s plume. To prove that hypothesis, a crew from the Netherlands plans to measure the chlorine chemistry of these shipping plumes, using special equipment to discover whether or not the methane is being oxidized in conjunction with the chlorine radicals given off by the sea spray.” (An interesting irony: on Friday, James Hansen, the world’s premier climate scientist, reported that one reason temperatures are rising right now is, as we necessarily switch off fossil fuels, the lowered levels of aerosol pollution in the atmosphere result in fewer clouds of smog blocking the sun. It is, as Hansen put it, a Faustian bargain come due. And one place that pollution is being reduced, he says, is in shipborne emissions, as mariners turn to cleaner fuels.)
If the Methane Action team’s hypothesis pans out, the scientists, most of whom are European, might be able to figure out how to amp up the scale of the reaction, to remove larger quantities of methane. They have proceeded carefully, getting scores of prominent climate experts to endorse studying the idea—Americans will recognize some of them, such as Michael Mann, of Penn State. (The United Nations Intergovernmental Panel on Climate Change gave the idea a nod in its most recent report.) Mann’s an interesting champion because, like many people in the climate movement, he has been unenthusiastic about the rapid adoption of another experiment that seems superficially similar: plans to “geoengineer” the atmosphere by pouring sulfur into it to block some of the sun’s rays.
There are major differences between these experiments. First, as Wysham points out, the smokestack “experiment is already underway, inadvertently, with iron in bunker fuels.” Second, the moral-hazard argument—the idea that, if you block the sun, oil companies will use it as an excuse to keep churning out fossil fuels—seems a little less pressing in this case: methane removal could become a tool for the fossil-fuel industry to keep fracking for natural gas, but most of the methane that must be removed actually doesn’t come from fossil fuels.
Job No. 1 is to end the combustion of fossil fuels, and fast; nothing can get in the way of that. But if, while we fight the fight, there are methods to ease the heat a little without tossing Big Oil a new lifeline, those are worth investigating.
Passing the Mic
Sunrun, the largest rooftop-solar-panel installer in the country, announced earlier this month that it had hired Mary Powell as its C.E.O. After a career making protective outerwear for dogs, Powell ran Green Mountain Power, Vermont’s main utility, where she focussed on sustainability. (Among other accomplishments, Green Mountain is the only utility in the country to have divested its pension fund from fossil fuels.) I wrote about some of Powell’s work in 2015, and got in touch with her again when I heard about her new appointment. (Our conversation has been edited for clarity and length.)
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