B. B. Cael, Jonah Bloch-Johnson, Paulo Ceppi, Hege-Beate Fredriksen, Philip Goodwin, Jonathan Gregory, Christopher J Smith, Richard G. Williams

The climate feedback determines how Earth's climate responds to anthropogenic forcing. It has been more negative in recent decades than predicted by Earth system models due to a sea surface temperature `pattern effect', whereby warming is concentrated in the western tropical Pacific, where nonlocal radiative feedbacks are very negative. This phenomenon has however primarily been studied within climate models. We diagnose a pattern effect from historical records as an evolution of the climate feedback over the past five decades. The climate feedback has decreased by $0.8\pm0.5$ W/m$^2$K over the past 50 years, corresponding to a reduction in climate sensitivity. Earth system models' climate feedbacks instead increase over this period. Understanding and simulating this historical trend and its future evolution are critical for reliable climate projections.