Comparing CMIP6 Future Projections for Severe Convective Environments in a Warmed Climate over Australia, Europe and North America

Severe thunderstorms are a global phenomena, producing a variety of hazards that include hail, tornadoes, damaging winds lightning and heavy precipitation. In the present climate, these events produce large losses to property and life. The warming climate is expected to influence these storm attributes, primarily through increasing thermodynamic instability driven by increased atmospheric moisture as warming occurs to near-surface temperatures. However, while a number of studies have explored how the climate system modulates these hazards through changes to favorable environmental conditions, these projections have generally been latitudinally biased away from the subtropics and focused on potentially aggressive warming scenarios. This presents a challenge to our understanding, as many parts of the world that currently regularly experience severe thunderstorms exist in different climate regimes or latitudes, and which exhibit non-linear responses to the warming climate.  Hence what is known for some latitudes and warming scenarios may not reflect a complete picture of the expected changes to hazards on a global level.

This presentation seeks to share newly developed insights into the frequency at which environments favorable to severe convection occur in particular regions, with a focus on identifying potential model biases. Extending from historical frequency, how these environments will evolve in response to moderately and strongly warmed scenarios in terms of both climate variability and change as projected using the latest generation of Coupled-Model Intercomparison Project Version 6 (CMIP6) data is explored. Results highlight that increases over the Northern and Western hemispheres are not necessarily reflective of changes in the subtropics and Southern hemisphere, and may respond differently depending on the environmental proxy used. While the driving mechanism of these changes are strong increases in CAPE, these changes can be modulated by local processes, and are often accompanied by factors that either resist convection (CIN), or seasonally may coincide with high likelihood of storm organization (S06, SRH).