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Thursday, January 30, 2020. 2:00PM. Energetic and heat-engine constraints on the spatial patterns of climate and climate change. Gerard Roe, University of Washington. Sponsored by NOAA GFDL. More information here. 

The climate system operates as a thermodynamic heat engine. A surplus of energy in the tropics and a deficit of energy in the high latitudes must be balanced with a poleward transport of energy by atmospheric and oceanic motions that ultimately do work against frictional dissipation. Sadi Carnot understood as much when formulating the laws of thermodynamics in the early nineteenth century. Atmospheric motions carry approximately eighty percent of the maximum poleward energy transport, and latent heat in the form of water vapor is a crucial component of this transport. Thus, the climatic patterns of temperature, evaporation, precipitation, the isotopic composition of water vapor, and even natural aerosols, are all linked through this transport. Recent research has demonstrated that atmospheric energy transport can be usefully approximated as a linear down-gradient transport of moist enthalpy. This single simple rule for transport explains many features of the mean climate, the predicted climate changes under global warming, and the spread of uncertainty among numerical climate models. Among these features are: polar amplification; the poleward migration of the subtropics, storm tracks, and jet stream under warming; uncertainty in model predictions maximizing in polar regions; hydrologic change as a function of climate state; and the sensitivity of the isotopic composition of precipitation to climate change.