Ground radiative measurements reveal negative longwave cloud feedback

Abstract Clouds profoundly influence Earth’s energy balance¹⁻². Observationally constraining cloud radiative feedback, a notably uncertain climate feedback mechanisms³⁻⁵, is crucial for improving predictions of climate change⁵⁻⁷. However, the quantification of cloud feedback faces challenges due to the complex effects of cloud changes on the energy balance, which are often entangled with the radiative impacts of other climate factors, and also due to the scarcity of long-term concurrent records of cloud properties and atmospheric radiation. In this work, we use an optimal spectral fingerprinting method designed to separate surface longwave cloud feedback from other surface forcings and feedbacks, by leveraging the unique spectral signatures of various meteorological variables in the long-term record of spectrally resolved downwelling longwave radiance at the Southern Great Plains site. We detect a prominent negative surface longwave cloud feedback, suggesting that cloud changes have a cooling effect on the surface and modulate the warming effect of increased greenhouse gas concentrations and atmospheric temperatures. Our findings establish a pivotal observational benchmark of radiative forcing and feedback needed for validating climate models.