Patterns and frequency of projected future tropical cyclone genesis are governed by dynamic effects

Potential future changes in the genesis frequency and distribution of tropical cyclones are important for society, yet uncertain. Confidence in the model projections largely relies on whether we can physically explain why the models projected such changes. Here we analyze multi-model climate simulations, and find that future changes in the patterns and frequency of tropical cyclone genesis are largely governed by dynamic effects-that is, by human-induced changes in the atmospheric circulation. These large-scale circulation changes include decreases in the mid-level upward motion and lower-to-mid level cyclonic vorticity, and increases in vertical wind shear. Conversely, the thermodynamic effect-a result of increased maximum potential intensity in a warmer climate-would yield tropical cyclone genesis patterns that are opposite to the model projections. We conclude that dynamic changes in response to anthropogenic greenhouse gas emissions are an important factor in determining the response of tropical cyclones to global warming.