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.