20 November 2018

Anthropogenic Influences on Major Tropical Cyclone Events

Understanding climate change influences on tropical cyclone wind speed and rainfall in historically destructive events.

Science

We discovered that climate change to date enhanced the rainfall of Hurricanes Katrina, Irma, and Maria, but did not change intensity based on wind speed. In addition, future anthropogenic warming would increase the wind speed and rainfall in 11 of 13 intense tropical cyclone events, out of 15 events sampled globally.

Impact

This research revealed possible increases in tropical cyclone rainfall beyond what would be expected from Clausius-Clapeyron scaling of increased temperature alone. In addition, comparison of regional climate model simulations with parameterized and resolved convection supports confidence in projections from global climate models with parameterized convection and tropical-cyclone-permitting resolution. 

Summary

There is no consensus on whether climate change has yet affected tropical cyclone statistics, owing to large natural variability and a limited period of consistent observations. In addition, projections of future tropical cyclone activity are uncertain, as they often rely on coarse-resolution climate models that parameterize convection and have difficulty in directly representing tropical cyclones. Here we used convection-permitting regional climate model simulations to investigate whether and how recent destructive tropical cyclones could change if these events had occurred in pre-industrial and in future climates. We found that, relative to pre-industrial conditions, climate change so far has enhanced the average and extreme rainfall of Hurricanes Katrina, Irma, and Maria, but did not change tropical cyclone intensity based on wind speed. In addition, future anthropogenic warming would increase the wind speed and rainfall in 11 of 13 intense tropical cyclone events (out of 15 events sampled globally). Additional regional climate model simulations suggest that convective parameterization introduces minimal uncertainty into the sign of projected changes in tropical cyclone intensity and rainfall, which supports confidence in projections from global climate models with parameterized convection and tropical-cyclone-permitting resolution. 

Contact
William D. Collins
Lawrence Berkeley National Laboratory (LBNL)
Publications
Patricola, C, and M Wehner.  2018.  "Anthropogenic Influences on Major Tropical Cyclone Events."  Nature 563(7731): 339-346, doi:10.1038/s41586-018-0673-2.