News•January 21, 2016

Indonesia’s Fires Blamed For Potent Greenhouse Gases

Indonesian fires that are expected to flare up again in the coming months may affect temperatures far away from the nation’s watery borders.

Carbon dioxide and methane from the fires is already known to be accelerating global warming, and new research is linking high levels of another potent greenhouse gas with forest and peat fires in Indonesia and elsewhere.

A forest fire in Indonesia.
Credit: CIFOR/Flickr

Analysis of tropospheric data gathered using specially-modified jets during Guam-based missions has linked elevated levels of ozone with forest fires. Like methane, ozone is a potent but short-lived greenhouse gas.

“Pretty much every time we were flying, we were seeing levels of ozone that were above what the air quality standard is in the U.S.,” said Daniel Anderson, a PhD candidate at the University of Maryland and one of the university and government scientists involved with the research. “We were interested in where that was coming from, since it’s far away from any polluting sources.”

The research linking the fires with the mid-tropospheric ozone was published last week in Nature Communications. It came as a surprise to many, and not all scientists involved with the Guam missions are ready to accept its conclusion without further proof. Other papers analyzing data gathered during the missions will be published by different teams of scientists in the months and years ahead.

Dissenting scientists point to evidence, including dry air found around the ozone and distinct layers of chemicals, that indicates to them that the greenhouse gas traveled not upward from fires into the tropical mid-troposphere, but instead wafted horizontally to it from cooler regions.

“These guys’ work is controversial,” said one of those scientists, National Center for Atmospheric Research atmospheric chemist Bill Randel. He said the fires might be responsible for “a component” of the ozone being studied, but he thinks nature is the main cause. “There’s a lively discussion going on.”

The Guam flights gathered detailed chemical information that’s not available using satellites. Alongside the molecules of ozone were telltale chemicals indicating the pollution plumes originated from forest fires, the large team of scientists led by Anderson concluded.

Models helped the scientists trace the genesis of the pollution plumes back to fires burning in Indonesia and other parts of southeast Asia as well as Africa.

Smoke from Indonesian forest fires blows over Singapore and Malaysia.
Credit: NASA Goddard Space Flight Center/Flickr

“These aren’t necessarily ‘wildfires’ — most of these fires are started by humans,” Anderson said. “If we can work to limit the emissions of these species that form ozone, then that would have a much more immediate impact on the climate than, say, reducing emissions of carbon dioxide.”

The sampling flights were conducted in the tropics of the western Pacific Ocean, but the findings would have ramifications for fires and temperatures in other parts of the world. The researchers didn’t attempt to quantify the effects of the ozone on regional warming, but Anderson and others say it’s important.

“Ozone is the third most important anthropogenic greenhouse gas, so any increase over natural background levels in the western Pacific is likely to have an observable effect on climate — not only in the tropics, but across the globe,” Anderson said.

The Indonesian fires are caused by land clearing for palm oil and acacia plantations, often lit deliberately, and often flaring up in drained swampland, where they burn heavily-polluting peat. The market for palm oil is global — and growing, found in many of the products sold from American supermarket shelves. The acacias are planted for the pulp and paper industry.

The blazes triggered public health crises through southeast Asia late last year. Analysis by the World Resources Institute suggested they were releasing more greenhouse gases every day than U.S. power plants. The fires were worsened by the ongoing El Niño, and another crippling bout of them is anticipated in February and March.

“The El Niño is driving the drought conditions that allow the fires to burn,” said Susan Minnemeyer, the nonprofit’s mapping and data manager, who has analyzed the problem. “But in Indonesia, it’s important to note that very few if any fires would occur naturally. Almost all the fires are occurring in land that has been drained.”

Larry Horowitz is a National Oceanic and Atmospheric Administration atmospheric chemist who wasn’t involved with Anderson’s study. Nor is he a member of the camp of scientists that disagrees with the findings. He said the paper could plausibly explain levels of tropospheric ozone, which were already known to be high in the area.

“I don’t totally believe it yet,” Horowitz said. “But it’s very suggestive that this is a possible mechanism.”