Simpson's Law and the Water Vapor Feedback

The 2021 Nobel prize in physics was awarded in part to Suki Manabe for the first credible calculation of Earth's climate sensitivity, including a proper treatment of the water vapor feedback which doubles that sensitivity. This talk will demonstrate how the strength of this water vapor feedback can be tied to a basic property of water vapor radiative transfer known as "Simpson's Law". Consideration of Simpson's Law allows for a quantitative, analytical estimate of the strength of the water vapor feedback, consistent with Manabe's early work as well as recent work employing satellite observations and a hierarchy of climate models.