Manabe’s Radiative–Convective Equilibrium

Syukoro (Suki) Manabe’s Nobel Prize in Physics was awarded largely for his early work on one-dimensional models of “radiative–convective equilibrium” (RCE), which produced the first credible estimates of Earth’s climate sensitivity. This article reviews that work and tries to identify those aspects that make it so distinctive. We argue that Manabe’s model of RCE contained three crucial ingredients. These are (i) a tight convective coupling of the surface to the troposphere, (ii) an assumption of fixed relative humidity rather than fixed absolute humidity, and (iii) a sufficiently realistic representation of greenhouse gas radiative transfer. Previous studies had separately identified these key ingredients, but none had properly combined them. We then discuss each of these ingredients in turn, highlighting how subsequent research in the intervening decades has only cemented their importance for understanding global climate change. We close by reflecting on the elegance of Manabe’s approach and its lasting value.