The turbulent future – a breath of fresh air

Abstract Ventilation of aerosol pollution within the planetary boundary layer (PBL) is dependent upon turbulent mixing, closely linked to the height of the PBL. Here, we show that emissions of both CO2 and absorbing aerosols influence the number of severe air pollution episodes through a boundary layer feedback loop, impacting turbulence and PBL height. While absorbing aerosols are known to cause increased boundary layer stability and reduced turbulence through atmospheric heating, we find CO2 to have the opposite effect over land through surface warming. Using the CMIP6 ensemble we find that in future scenarios with increasing CO2 and reduced aerosol emissions, around 10% of the world’s population currently living in regions with high pollution levels are likely to experience a particularly strong increase in turbulence and PBL height, and thus a reduction in intense pollution events. Our results clearly underline the importance of BC mitigation for reducing the most severe exposures to air pollution.