Abstract.

Earth’s albedo (reflectivity) declined over the 25 years of precise satellite data, with the decline so large that this change must be mainly reduced reflection of sunlight by clouds. Part of the cloud change is caused by reduction of human-made atmospheric aerosols, which act as condensation nuclei for cloud formation, but most of the cloud change is cloud feedback that occurs with global warming. The observed albedo change proves that clouds provide a large, amplifying, climate feedback. This large cloud feedback confirms high climate sensitivity, consistent with paleoclimate data and with the rate of global warming in the past century.

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See also: Global Warming Has Accelerated: Are the United Nations and the Public Well-Informed?

(A doubling of atmospheric carbon dioxide concentration over pre-industrial level would result in an average warming of 4.5°C, not 3°C as previously thought.)