When you think of greenhouse gas emissions, you might be thinking of carbon dioxide—but methane is another significant contributor to warming that’s on the rise. Sources include large grassfires, leaking natural gas wells, natural wetland processes, belching cows, or even farting termites. But the relative contribution of each of these sources to Africa’s methane mix has been hard to track. And that’s important data to have, because the tropics account for 40 percent of global emissions. Last month, researchers report in Geophysical Research Letters, that a drone on a remote tropical island may solve that mystery.
The magic of Ascension Island, located in the middle of the South Atlantic, is the way the air flows, says Rebecca Brownlow, an atmospheric science Ph.D. student at Royal Holloway, University of London. Above about 1.6 kilometers from sea level, the air is coming straight from southeast Africa. Below it is the South Atlantic’s mix. Subtracting that from the African air gives a good sense of how much methane is generated in Africa. And the best means of making those measurements is with a high-flying drone.
“There was no other way to take these samples and to make these measurements,” says Rick Thomas, an atmospheric scientist at the University of Birmingham in the United Kingdom. Existing methane ground monitoring stations in Africa can’t discern region-wide effects, because they can’t tell how methane would end up mixing in the atmosphere.
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