This project seeks to advance our understanding of the climate impacts of ship emissions and to better assist relevant policymaking aimed at mitigating such emissions. It is apparent that exclusion of detailed dynamical aerosol-climate interactions in the coupled ocean-atmosphere system in previous studies has been a major bottleneck in revealing the full spectrum of climate impacts associated with pollutants emitted by international shipping. This analysis will thus emphasize the much more complex climate impacts of particulate matter induced by international shipping, both through direct emissions (e.g., black carbon and organic carbon) and gas-to-particle production (e.g., sulfate aerosols formed by ship emitted sulfur dioxide). These impacts range from changes in surface temperature to amounts and distributions of clouds and precipitation. The climate impacts of aerosols, particularly those occurring through indirect effects, cannot be simply extrapolated based on the forcing-response relationship for the long-lived greenhouse gases. Using their “state-of-the-science” interactive aerosol–climate system model, CESM-MARC, which includes all the major components from atmosphere, ocean, land and cryosphere, the researchers aim to determine the full consequences for climate resulting from the multiple aerosol–cloud–climate interactions associated with ship emissions. Through model simulations, they propose to quantify the difference in climate impacts between two future shipping scenarios, one with fuel sulfur content at its current 3.5 percent level, and another with a proposed reduction of sulfur level to 0.50 percent, both targeted at a timeframe around 2020–2025.