Consistent responses to black carbon and carbon dioxide at global and 100 m model resolutions

Abstract Climate responses to external forcings involve processes across a wide range of scales. While the ability of climate models to accurately simulate these responses remains uncertain, the computational cost of high-resolution models limits their use for long-term simulations. However, key atmospheric processes are initiated within days of a perturbation, suggesting that initial responses may offer valuable insight into resolution-dependent differences. Here we investigate initial climate responses to increased carbon dioxide and black carbon using a regional climate model at five resolutions, from 62.5 km to 100 m. Despite large differences in grid spacing, responses in radiative fluxes and temperature are remarkably consistent. Cloud responses are generally similar, though summer differences emerge, while precipitation shows stronger resolution dependence. These results suggest that even coarse-resolution models can capture key elements of the initial climate response, supporting their use in estimating climate impacts and informing confidence in their representation of atmospheric processes.