A Major Combustion Aerosol Event Has No Impact on the Atmospheric Ice-Nucleating Particle Concentration

As significant increases in emissions of combustion aerosol related to anthropogenic activities continue to be observed, there is the potential that these aerosol types may exert a climate forcing through cloud glaciation. Atmospheric measurements of ice-nucleating particle (INP) concentrations between −5 and −34 °C during the UK’s annual Bonfire Night celebrations, comprising major combustion aerosol events, showed that the rise in aerosol concentration due to the emission of combustion aerosol was decoupled from the INP concentration in the atmosphere (Figure 1). This was despite more than a factor of 10 increase in aerosol number concentrations and more than a factor of 100 increase in black carbon (BC) mass concentration. This suggests that BC and other combustion aerosol did not compete with the INPs present in the ambient environment. We conclude that combustion aerosol generated by events similar to Bonfire Night are not a primary source of INPs in typical mid-latitude terrestrial locations where the background INP concentrations are within the expected range for that region.