Global distribution and warming effect of brown carbon from shipping emissions

Emissions of shipping have great influences on atmospheric environment and global climate with the growth of maritime trade. Previous studies identified that shipping black carbon (BC) constitutes the main aerosol component that responsible for light absorption, while shipping organic carbon (OC) was generally considered non-absorbing. Recent studies have indicated that organic components derived from shipping emissions exhibit light absorption at short wavelengths (brown carbon, BrC). However, there is a lack of quantification regarding the absorption effects of shipping BrC. This study investigates the radiative absorption effect (RAE) of shipping BrC, updating models with measured shipping BrC light absorption ability. Surface concentrations of shipping BrC contribute ~ 40% to fossil fuel OC. The global annual average RAE of shipping BrC is +0.15 to +0.36 mW m⁻², peaking in boreal summer. The warming effect of shipping BrC is 8%–19% relative to shipping BC. With the low-sulfur standard, the RAE of shipping BrC increases to +0.52 mW m⁻², which is close to that of shipping BC (+0.52 mW m⁻²) and could offset ~ 40% of direct cooling effect of shipping sulfate. For the radiative absorption of shipping aerosols, BrC is an important part, whose contribution is greater with the upgrade of ship fuels.