Tracing Black Carbon's Historical Impact on Regional Precipitation

Black carbon (BC) aerosols, strong absorbers of solar radiation, induce atmospheric heating, altering vertical profiles of temperature, water vapor, and clouds. These impacts can lead to localized precipitation changes, and may also initiate changes to atmospheric circulation, with potentially far-reaching impacts on precipitation patterns.

While prior studies suggest BC's significant influence on precipitation, its role in both local and remote precipitation change remains insufficiently quantified. To address this gap, we explore the extent to which historical BC emissions have shaped regional precipitation. Specifically, we ask: how much could future BC changes influence regional precipitation, based on insights from the historical period?

Using the Community Earth System Model version 2 (CESM2), we have generated a 20-member ensemble of simulations of 1950–2014 with anthropogenic BC emissions fixed at 1950 levels. By comparing these to standard historical simulations with evolving emissions, we isolate the impacts of BC emission trends from 1950 to 2014 on global and regional climates.

Our results reveal that BC emissions have caused localized drying in regions of high emissions, notably over Europe during the 1980s–1990s and Eastern China in the early 21st century. Furthermore, we find indications that BC exerts a dampening effect on the most extreme precipitation events, highlighting its historical role in modulating climate extremes.