Source of 2015 Southeast Asia smoke cloud found

During the prolonged conflagration, which was triggered by an El Nino-driven drought, scientists collected smoke particles on the campus of the National University of Singapore and sent the samples to their colleagues at the University of California, Irvine. UCI's researchers dated the isotopes of the particles' carbon atoms, finding them to have an average age of 800 years.

Combining this analysis with atmospheric modeling of the wind-driven movement of smoke plumes in fall 2015, the team sleuthed out the source of the harmful cloud: smoldering peat on the islands of Borneo and Sumatra. The findings were published today in Proceedings of the National Academy of Sciences.

"Our research shows that almost all of the smoke emissions originated from the burning of Holocene-aged peat," said first author Elizabeth Wiggins, a postdoctoral research fellow at NASA's Langley Research Center who led the study as a Ph.D. candidate in Earth system science at UCI, graduating in 2018. "Although this peat has functioned as a massive terrestrial carbon storage reservoir over the last several thousand years, it is now a significant source of carbon to the atmosphere."

The scientists' work provides independent confirmation that Indonesian peats were the flashpoint of the blazes, highlighting the role of humans in the environmental catastrophe.