Photo: A NASA satellite image shows smoke from fires over Indonesia in 2015. Credit: NASA Earth Observatory The season of massive fires that ravaged Indonesian forests last year was the most severe in terms of pollution since NASA began tracking such fires from space in the early 2000s, and pumped a quantity of carbon emissions into the air that was somewhere between the entire annual outputs of Japan and India.
The burning trees created a plume of smoke that stretched from East Africa to the western Pacific Ocean, and lasted for two months after the fires finally were extinguished.
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That's from a new study published in Proceedings of the National Academy of Sciences, which also predicted that the disaster -- which was caused by deliberate setting of fires to clear land for agriculture -- is likely to repeat itself.
Columbia University associate research scientist Robert Field, the study's lead author, told New Scientist that the fires polluted the atmosphere on a scale that normally is seen only with large volcanoes.
"I don't know of any other sources other than volcanoes that have had such a pronounced signature as we saw with the carbon monoxide stretching halfway around the world at the equator," he explained to the British science publication.
Field, who with his colleagues relied upon date from five different satellite instruments to make their calculations, estimated that about 15 million people in Indonesia and neighboring Asian countries were at risk of respiratory damage because of exposure to the smoke.
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By combining those observations with meteorological data, the scientists determined that massive Indonesian fires often happen in association with dry conditions that occur during El Niño, a warm mass of water in the Pacific that alters weather conditions in many places across the globe. When the average daily rainfall decreases to less than four millimeters, or 0.16 inches, that seems to be a "tipping point" that creates conditions in which fires can spread massively.
That knowledge could help Indonesians to anticipate massive fires and possibly reduce the risk -- but only if they're willing to stop clearing vegetation by burning it. The World Resources Institute says that Indonesia is the world's fifth biggest producer of greenhouse gases, mainly due to its practice of burning down forests and peatlands rich in carbon.
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