Anthropogenic climate change contribution to wildfire-prone weather conditions in the Cerrado and Arc of deforestation

Sihan Li,Imma Oliveras,Sami W Rifai,David Wallom,Folmer Krikken,Sarah N Sparrow,Yadvinder Malhi,Friederike E L Otto,Liana O Anderson

doi:10.1088/1748-9326/ac1e3a

Abstract

2015 saw the strongest El Niño event in the historical record, resulting in extreme drought conditions in Brazil. As drought conditions may also lead to greater fire danger, this study uses the 2015 fire in Brazil as a case study to examine whether and to what extent human-induced climate change has contributed to the fire weather conditions in the Cerrado and the southern Amazonia transitional forests known as the Arc of deforestation. Our results show that anthropogenic climate change is indeed a driver of meteorological conditions conducive to strong fire weather in these two regions, measured by fire weather index (FWI), especially on shorter timescales of daily and weekly. The anthropogenic climate change signal of FWI on short timescales corresponds to a similar order of increase in the FWI sub-indices (initial spread index and fine fuel moisture code) that can rapidly change due to the influence of the instantaneous weather conditions. For both regions the changes in fire weather in response to anthropogenic climate change are dominated by the combination of temperature and relative humidity responses. High FWI is more likely to occur under El Niño conditions, less likely under La Niña conditions, although the impacts of El Niño vs La Niña conditions are not symmetric when compared with El Niño Southern Oscillation neutral states. To summarize, both human-induced climate change and the presence of El Niño increased the likelihood of occurrence for the strong fire weather condition in 2015. Our results suggest that local and regional adaptation measures, such as improved drought monitoring and warning systems, could help with effective planning of fire prevention, firefighting actions, and disaster preparedness.

Highlights

Fire ignitions largely originate from human activities, climate and weather can be key factors of the spread and growth of fires (Barbero et al 2015)
La Nina conditions are not symmetric when compared with El Nino Southern Oscillation neutral states. Both human-induced climate change and the presence of El Nino increased the likelihood of occurrence for the strong fire weather condition in 2015
Regions of interest The geographical focus was primarily the Cerrado region, which was severely affected as measured in Burned area (BA); we looked at eastern Para and northern Mato Grosso known as the ‘Arc of deforestation’, as a secondary geographical focus

Summary

Introduction

Fire ignitions largely originate from human activities, climate and weather can be key factors of the spread and growth of fires (Barbero et al 2015). The observed changes in fire activity over recent decades in Brazil (Aragao et al 2018) underscores the need for a better understanding of the relationship between meteorological conditions favorable for wildfires (i.e. fire weather conditions), natural climate variability, drivers outside the climate system (ignition causes, fire management, etc), and the role of anthropogenic climate change. This is needed for developing reliable fire models to improve projections of fire activities and shifting fire regime patterns, and to better support local fire management policies.

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