Numerical experiments have revealed the importance of horizontal transport of light in the presence of clouds (“3D effects’), with consequences for climate, weather and solar resource availability predictions. Yet, atmospheric models continue to use 1D radiative transfer schemes. In this paper, we provide observational evidence for 3D effects. Observed direct and diffuse surface fluxes are compared to outputs from the ecRad radiative transfer scheme run on retrieved cloud profiles. The direct-beam calculation takes careful account of the field-of-view of the pyrheliometer to ensure consistency between observed and modeled direct fluxes. Only the solver that accounts for 3D effects is able to reproduce the observed mean direct–diffuse partition of surface fluxes as a function of solar zenith angle and cloud cover. This validates the physically-based model for 3D radiative processes included in ecRad. These results are in favor of a shift of paradigm from 1D to 3D radiation in large-scale models.