Response of dust emissions in southwestern North America to 21st century trends in climate, CO₂ fertilization, and land use: Implications for air quality

Climate models predict a shift toward warmer and drier environments in southwestern North America. However, the projected dust trends under climate change are sometimes contradictory. Here we link a dynamic vegetation model (LPJ-LMfire) to a chemical transport model (GEOS-Chem) to assess the impacts of future changes in climate, CO2 fertilization, and land use practices on dust mobilization, and to investigate the consequences for surface air quality. Considering all factors in the most extreme future warming scenario, we find decreasing trends of fine dust emissions over Arizona and New Mexico but increasing emissions along Mexico's northern border in the late-21st century during springtime, the season of maximum dust emissions. These trends result from more densely vegetated environments in the arid southwestern U.S. under future climate, but sparser vegetation in northern Mexico. The two main drivers of dust trends in this region – CO2 fertilization and land use intensification – play opposing roles, with the first driver enhancing vegetation and thus decreasing dust in the southwestern U.S. and the second driver increasing dust in northern Mexico. In the absence of CO2 fertilization, the RCP8.5 scenario places an upper bound on increases in dust, with elevated concentrations widespread over the southwestern North America by 2100 in spring, especially in southeastern New Mexico (up to ~2.0 µg m−3) and along the border between New Mexico and Mexico (up to ~2.5 µg m−3).