Analysis and evaluation of past tropical cyclone trends, assessments and simulations regarding a possible future scenario, using models provided by CMCC.

A tropical cyclone (TC) is a rapidly rotating storm that develops over oceans at tropical latitudes and can vary in speed, size, and intensity. Together with other extreme events, their growing impact on society is a consequence of climate change, induced by natural forcings and human activity, mostly through emissions of greenhouse gases (GHGs) that alter the chemistry of the atmosphere. This document presents one of the possible future scenarios concerning the evolution of TCs, using simulation ran by the CMCC-CM3-LT (Centro Euro-Mediterraneo sui Cambiamenti Climatici – Climate Model version 3) model for the present (1980–2010) and future climate (2070–2100) according to the SSP5-8.5 (Shared Socioeconomic Pathway $\#$5) scenario. The reliability of the data produced by CMCC-CM3-LT is confirmed by comparison with observational and reanalysis datasets. Then, surface wind and mean sea level pressure (MSLP) variables are used as input for the TC tracking performed by CyTRACK. Based on Accumulated Cyclone Energy (ACE) and minimum central pressure (MCP), the model suggests an increasing trend in TC intensity in the Central and Eastern North Pacific Ocean and the North Indian Ocean. Conversely, an opposite tendency is observed in the South Pacific and in the regions of the Indian and Western Pacific Oceans at low latitudes. Although spatially heterogeneous, the Atlantic Ocean also shows a general decrease in ACE. Consistent with the evolution of ACE and MCP, the size of cyclones follows the variation in intensity, with TCs being larger when more intense and vice versa. Looking instead at the frequency with which TCs are generated, a clear upward trend is revealed near all coasts, as well as in the Central North Pacific Ocean and in a strip right below the equator in the Eastern Pacific Ocean. In contrast, a notable decrease in TC occurrence is projected for the Western Pacific and the Eastern Indian Ocean away from the Australian coasts.In terms of duration, future cyclones show a distribution similar to the present one, but with a shift toward shorter durations, suggesting a potential decrease in the persistence of extreme events. Hence, in regions where ACE remains unchanged or increases, this behavior suggests that the intensification is primarily driven by increased storm intensity rather than prolonged duration.