El Niño Driven Changes in Global Fire 2015/16

Ted R Feldpausch,Richard A Betts,Liana O Anderson,Chris D Jones,Manoel Cardoso,Chantelle Burton

doi:10.3389/feart.2020.00199

Abstract

El Niño years are characterised by a high sea surface temperature anomaly in the Equatorial Pacific Ocean, which leads to unusually warm and dry conditions over many fire-prone regions globally. This can lead to an increase in burned area and emissions from fire activity, and socio-economic and environmental losses. Previous studies using satellite observations to assess the impacts of the recent 2015/16 El Niño found an increase in burned area in some regions compared to La Niña years. Here, we use the dynamic land surface model JULES to assess how conditions differed as a result of the El Niño by comparing simulations driven by observations from the year 2015/16 with mean climatological drivers of temperature, precipitation, humidity, wind, air pressure and short and long-wave radiation. We use JULES with the interactive fire module INFERNO to assess the effects on precipitation, temperature, burned area, and the associated impacts on the carbon sink globally and for three regions: South America, Africa and Asia. We find that the model projects a variable response in precipitation, with some areas including northern South America, southern Africa and East Asia getting drier, and most areas globally seeing an increase in temperature. As a result, higher burned area is simulated with El Niño conditions in most regions, although there are areas of both increased and decreased burned area over Africa. South America shows the largest fire response with El Niño, with a 13% increase in burned area and emitted carbon, corresponding with the largest decrease in carbon uptake. Within South America, peak fire occurs from August to October across central-southern Brazil, and temperature is shown to be the main driver of the El Niño-induced increase in burned area during this period. Combined, our results indicate that although 2015/16 was not a peak year for global total burned area or fire emissions, the El Niño led to an overall increase of 4% in burned area and 5% in emissions compared to a ‘No El Niño’ scenario for 2015/16, and contributed to a 4% reduction in the terrestrial carbon sink.

Highlights

The El Niño Southern Oscillation (ENSO) is a reasonably predictable mode of variability that occurs every 2–7 years, and can have a large impact on regular rainfall patterns and temperatures on a global scale
We have assessed the impact of the 2015/16 El Niño on fire and on the terrestrial carbon cycle by using the JULES-INFERNO model with an experiment comparing the observed 2015/16 El Niño to an average climatology from the previous 10 years
Burned area was impacted by the El Niño, with some areas showing an increase in burned area, and others showing a decrease (Africa, East Asia)

Summary

Introduction

The El Niño Southern Oscillation (ENSO) is a reasonably predictable mode of variability that occurs every 2–7 years, and can have a large impact on regular rainfall patterns and temperatures on a global scale. It is the biggest driver of variability in the terrestrial carbon cycle, dominated by the response in the tropics (Cox et al, 2013; Betts et al, 2016). The El Niño phase of ENSO commonly results in higher temperatures and reduced precipitation across the tropics, the timing of this varies globally (Chen et al, 2017). The impacts across continents can be variable, for example southern South America often experiences wetter conditions, while northern, and central-east regions experience drought (Grimm, 2003; Stauffer, 2015)

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Conclusion