Can low-resolution CMIP6 ScenarioMIP models provide insight into future European post-tropical-cyclone risk?

Abstract

Post-tropical cyclones (PTCs) can cause extensive damage across Europe through extreme winds and heavy precipitation. With increasing sea surface temperatures, tropical cyclones (TCs) may form and travel further poleward and eastward than observed historically. Recent work has suggested that the frequency of intense Europe-impacting PTCs may increase substantially in the future. Using an objective feature-tracking scheme and TC identification method, we track and identify the full life cycle of TCs in the North Atlantic in five CMIP6 climate models in the historical (1984-2014) period and in the future under the SSP5-85 scenario (2069-2099). These five models are selected based on their ability to simulate TC frequency similar to observed in the North Atlantic, although model deficiencies remain. We find no robust changes in Europe-impacting PTC frequency or intensity in the future. This is because two competing factors - a significant decrease in TC frequency of 30%-60% and an increase in the proportion of TCs reaching Europe - are approximately the same size. The projected increase in the proportion of TCs reaching Europe is largely driven by an increase in the likelihood of recurvature and is consistent with projected decreases in vertical wind shear and increases in potential intensity along the US East Coast in the future. The projected increased likelihood of recurvature is also associated with a shift in TC genesis away from the main development region, where model biases cause very few TCs to recurve. This study indicates that large uncertainties surround future Europe-impacting PTCs and provides a framework for evaluating PTCs in future generations of climate models.