Human-driven greenhouse gas and aerosol emissions cause distinct regional impacts on extreme fire weather

Danielle Touma,Flavio Lehner,Sloan Coats,Samantha Stevenson

doi:10.1038/s41467-020-20570-w

Abstract

Attribution studies have identified a robust anthropogenic fingerprint in increased 21st century wildfire risk. However, the risks associated with individual aspects of anthropogenic aerosol and greenhouse gases (GHG) emissions, biomass burning and land use/land cover change remain unknown. Here, we use new climate model large ensembles isolating these influences to show that GHG-driven increases in extreme fire weather conditions have been balanced by aerosol-driven cooling throughout the 20th century. This compensation is projected to disappear due to future reductions in aerosol emissions, causing unprecedented increases in extreme fire weather risk in the 21st century as GHGs continue to rise. Changes to temperature and relative humidity drive the largest shifts in extreme fire weather conditions; this is particularly apparent over the Amazon, where GHGs cause a seven-fold increase by 2080. Our results allow increased understanding of the interacting roles of anthropogenic stressors in altering the regional expression of future wildfire risk.

Highlights

Attribution studies have identified a robust anthropogenic fingerprint in increased 21st century wildfire risk
We quantified the probability of extreme fire weather over the fully forced (ALL) and all-but-one forced (X) Community Earth System Model version 1 Large Ensemble (CESM-LE and CESM-LE-SF, repsectively) simulations, and assessed the effect of aerosol emissions, greenhouse gas emissions, biomass burning emissions, and landuse/land-cover change (LULC) on extreme fire-weather risk over the historic and future periods
Anthropogenic greenhouse gas emissions have already doubled extreme fire-weather risk in some regions compared to a world with emissions fixed to preindustrial (1920) levels, and they will continue to increase extreme fire-weather risk throughout the 21st century

Summary

Introduction

Attribution studies have identified a robust anthropogenic fingerprint in increased 21st century wildfire risk. By mid-2020, the Siberian tundra had already experienced a more severe fire season than the previous record-breaking year under extreme heat conditions attributed to anthropogenic climate change, and the Amazon rainforest was predicted to exceed 2019’s record number of observed fires Consistent with these recent increases in extreme fire weather, future anthropogenic climate change is expected to continue to increase the frequency and severity of wildfires. Understanding fire risk at a regional scale is important for mitigation and planning purposes It is unclear how the competing influences of greenhouse gases, aerosols due to industrial and biomass burning activities, and land-use/land-cover change (LULC) have historically and will continue to modify regional fire-relevant climate conditions. Earth System Model version 1 (CESM1) capable of isolating individual climate forcings[22,23] to show that anthropogenic greenhouse gases, industrial and biomass burning aerosol emissions, and LULC have distinct influences on regional wildfire risk, both historically and under projected future climate change. Quantifying the regional expressions of anthropogenic forcing on extreme fire-weather risk could aid in climate change mitigation and adaptation strategies

Methods

Results

Conclusion