Atmospheric Concentration of Black Carbon over Africa: Hotspot Regions, Seasonal Dynamics and Future Projections from Bias-Adjusted AerChemMIP Models

Abstract. Black carbon (BC) is one of the most potent short-lived climate forcers, accelerating global warming and posing risks to human health. Despite its climatic and health implications, BC remains poorly characterized across much of Africa. Here, we use bias-adjusted Aerosol Chemistry Model Intercomparison Project (AerChemMIP) simulations to identify hotspot regions, analyse long-term trends and assess key drivers of its spatial-temporal changes. Although models reproduce the spatial patterns of BC, they systematically underestimate concentration over Central Africa. The bias-adjusted simulations indicate that BC concentration is highest in Central Africa, where annual mean values exceed 1.5 µg m⁻³ and seasonal peaks reach approximately 3 µg m⁻³, while North Africa and Madagascar exhibit much lower concentration (0.1 µg m⁻³). Seasonal dynamics is dominated by dry-season enhancements driven by biomass burning while lower concentration is detected during the wet season due to reduced burning activities and enhanced wet deposition. In addition, long-range transport of BC from Europe enhances concentration in North Africa. The Sen’s slope and Mann-Kendall trend test revealed significant BC increase in regions with rapid economic development such as southern Nigeria, central Ethiopia, Rwanda and northern Egypt. Future projections under SSP370SST show continued BC increase (~0.5–1.0 % yr⁻¹) in North, West and East Africa until mid-century while a significant decrease in parts of Central and Southern Africa until late-century. These findings highlight the need for targeted control strategies and stronger regulatory policies to reduce BC concentration in hotspot regions while sustaining and reinforcing mitigation efforts in regions with declining trends.