International shipping emissions (ISE) can influence the global radiation budget. Using an Earth system model, we derive a significant global cloud radiative effect (CRE) of ISE (−0.153 W m⁻²) when using current emissions. This CRE would become weaker (−0.001 W m⁻²) if a more stringent regulation were adopted. The CRE would achieve a significant enhancement when a lower DMS emission is prescribed. These findings suggest a reevaluation of the ISE-induced CRE with consideration of DMS variability.