Potential Intensity in Current and Future Climates: Sources of Error in Historical HighResMIP Simulations

Recent work suggests that the lifetime maximum intensity (LMI) of the strongest tropical cyclones (TCs) have trended stronger over the historical record and that similar trends may occur in a warmed climate. The potential intensity (PI), which represents the theoretical upper limit to TC intensity within a given environment, is a function of sea surface temperature (SST), mean sea level pressure, and vertical profiles of temperature and moisture. These dependencies allow for the PI to capture the improving TC thermodynamic environments within the observed record and is likely why PI has been shown to correlate with increasing LMIs. The relative intensity is defined as the fraction of the PI obtained by an observed TC. If increases in PI and LMI are equal, the relative intensity would not change. Using ERA5 reanalysis data and historical TC data from the International Best Track Archive for Climate Stewardship (IBTrACS), we first establish a climatology of LMI, PI, and relative intensity from 1980-2022 for the globe and individual TC basins. Trends in observed LMI are revisited, and trends in relative intensity are computed. The observed climatologies and trends are then compared with the equivalent from global climate models in control and warmed scenarios. Comparing observations to global climate model simulations is important to increase confidence in future projections.