Responses of tropical cyclones to CO2 emission reductions

Abstract

Numerous prior studies have discussed the impact of global warming on Tropical Cyclones (TCs). However, there's a lack of understanding regarding TC activity post-global warming. In this study, through CO2 emission-driven experiments ensemble experiments within CESM2 model, simulations of 400 years for scenarios involving Net-zero Emission CO2 (ZEC) and negative emission CO2 (IRCC) are conducted to analyze the responses of TC activity to CO2 removal forcing. Using the Okubo-Weiss-Zeta Parameter (OWZP) method for TC detection, which is independent of the model's resolution, we identified a hemispheric asymmetry emerged where TC activity increased in the Northern Hemisphere while decreasing in the Southern Hemisphere although CO2 concentrations returned to pre-increase levels. This indicates that even if humanity achieves net-zero CO2 emissions, such hemispheric-asymmetry of responses may remain unrecoverable. Specifically, irreversible responses are prominent in the North Atlantic, the Eastern Pacific, and the West Pacific in the Northern Hemisphere, and the South Pacific in the Southern Hemisphere. Hemispheric-asymmetry of TC activity is influenced significantly by changes in mainly mid-level relative humidity and Vertical Wind Shear (VWS) due to alterations in Hadley circulation and zonal circulation. Beyond TC frequency, we analyzed shifts in TC genesis location and track, linking them to environmental changes. These findings emphasize the necessity to regionally differentiate preparations for the TC activity based on CO2 reduction scenarios.