Quantifying the Cooling Effect of Tropical Cyclones on the Climate System

The net radiation due to 20 years of global tropical cyclones is calculated and the corresponding contribution to the earth energy balance is analyzed. Through their clouds, tropical cyclones are shown to increase the upwelling radiation at the top of the atmosphere compared with the clear sky condition. This provides an overall cooling effect on the climate system by increasing reflected shortwave (cooling) and decreasing emitted longwave (warming) radiation. The amount of cooling represents a considerable fraction of the excess warming energy in the climate system, but it is opposite in sign. While there are some tropical cyclones with net-warming effect, the majority are net cooling and these tend to represent both more intense and earlier-season systems. Current understanding predicts an increase in the proportion of intense tropical cyclones due to a warming climate, so this cooling effect serves as potential negative feedback on the warming climate system.