Atmospheric Chemistry and Physics Aerosol indirect effects from shipping emissions: sensitivity studies with the global aerosol-climate model ECHAM-HAM

Abstract. In this study, we employ the global aerosol-climate model ECHAM-HAM to globally assess aerosol indirect ef-fects (AIEs) resulting from shipping emissions of aerosols and aerosol precursor gases. We implement shipping emis-sions of sulphur dioxide (SO2), black carbon (BC) and partic-ulate organic matter (POM) for the year 2000 into the model and quantify the model’s sensitivity towards uncertainties as-sociated with the emission parameterisation as well as with the shipping emissions themselves. Sensitivity experiments are designed to investigate (i) the uncertainty in the size dis-tribution of emitted particles, (ii) the uncertainty associated with the total amount of emissions, and (iii) the impact of reducing carbonaceous emissions from ships. We use the results from one sensitivity experiment for a detailed discussion of shipping-induced changes in the globa