Future Fire Impacts on Smoke Concentrations, Visibility, and Health in the Contiguous United States

Abstract

Fine particulate matter (PM2.5) from U.S. anthropogenic sources is decreasing. However,
\nprevious studies have predicted that PM2.5 emissions from wildfires will increase in the midcentury to next
\ncentury, potentially offsetting improvements gained by continued reductions in anthropogenic emissions.
\nTherefore, some regions could experience worse air quality, degraded visibility, and increases in
\npopulation-level exposure. We use global climate model simulations to estimate the impacts of changing fire
\nemissions on air quality, visibility, and premature deaths in the middle and late 21st century. We find that
\nPM2.5 concentrations will decrease overall in the contiguous United States (CONUS) due to decreasing
\nanthropogenic emissions (total PM2.5 decreases by 3% in Representative Concentration Pathway [RCP] 8.5
\nand 34% in RCP4.5 by 2100), but increasing fire-related PM2.5 (fire-related PM2.5 increases by 55% in RCP4.5
\nand 190% in RCP8.5 by 2100) offsets these benefits and causes increases in total PM2.5 in some regions.
\nWe predict that the average visibility will improve across the CONUS, but fire-related PM2.5 will reduce
\nvisibility on the worst days in western and southeastern U.S. regions. We estimate that the number of deaths
\nattributable to total PM2.5 will decrease in both the RCP4.5 and RCP8.5 scenarios (from 6% to 4–5%), but
\nthe absolute number of premature deaths attributable to fire-related PM2.5 will double compared to early
\n21st century. We provide the first estimates of future smoke health and visibility impacts using a
\nprognostic land-fire model. Our results suggest the importance of using realistic fire emissions in future air
\nquality projections.