Asymmetric response of the Western North Pacific tropical cyclone genesis to symmetric CO2 pathway

Abstract

The responses of the western North Pacific (WNP) tropical cyclone (TC) genesis and associated large-scale atmospheric environment to varying CO₂ pathways are investigated using an idealized CO₂ removal experiment. In the experiment, CO₂ concentration is first increased at the rate of 1% year⁻¹ until quadrupled and then decreased at the same rate until it reaches the initial level. Our results indicate asymmetric changes in WNP peak-season (July–September) TC genesis between CO₂ ramp-up and ramp-down periods, showing a significant reduction of TC genesis over the Philippine Sea and landfalling TCs in East Asia when the CO₂ concentration is reduced. Such TC activity changes are attributed to the development of WNP anticyclonic circulation in the ramp-down period, in association with an El Niño-like delayed response in sea surface temperature. This asymmetric response of WNP TC activities to symmetric CO₂ pathway may provide a reference for regional TC disaster prevention and preparations under mitigation conditions.