A negative feedback on El Niño events caused by extreme fire activity in equatorial Asia

Abstract

Abstract Large peatland fires in equatorial Asia during recent El Niño years have resulted in widespread smoke pollution, with record-breaking impacts on air quality and carbon emissions. Here we show that large fires during El Niño years also create a negative feedback on El Niño intensity and regional teleconnections. By comparing climate model simulations using prescribed fire emissions from a strong El Niño event versus from a non-El Niño year, we show that El Niño-enhanced fire emissions result in large surface cooling and atmospheric heating of up to 40 Wm− 2 over much of equatorial Asia. This atmospheric heating shifts cloud cover westward in the Pacific, increasing cloud amount and precipitation over equatorial Asia, and strengthening the tropical Walker circulation. This opposes the typical El Niño circulation in the Pacific, and drives a sizeable reduction in peak sea surface temperature anomalies over the Niño 3.4 region by around 0.4 K, or 22%.