Regionally asymmetric hysteresis of western North Pacific tropical cyclone activity in a CO₂ removal experiment

Tropical cyclones (TCs) are devastating natural phenomena with considerable socio-economic impacts on coastal regions worldwide. Despite their importance for climate mitigation and adaptation planning, the response of TC activity to carbon dioxide removal (CDR) has received limited attention. Here, we examine the influence of CDR on TC activity over the western North Pacific (WNP) using an Earth system model under an idealized CDR scenario. Our results show that the WNP-mean genesis potential index (GPI) does not exhibit hysteresis between the ramp-down (model years 249-279) and ramp-up (model years 0-30) periods. This lack of hysteresis is attributed to a regionally asymmetric GPI hysteresis, characterized by a west-east dipolar pattern. The dipole is primarily driven by changes in vertical wind shear associated with a weakened Walker circulation, which is in turn linked to hysteresis in El Niño-like sea surface temperature patterns. Additional simulations using a higher-resolution atmospheric model confirm these findings, revealing no significant change in the number of TCs over the WNP between the two periods. However, a notable 20.11% decrease in TC landfall frequency in East Asia is identified, attributed to reduced TC genesis over the western part of the WNP between the two periods. These results suggest that CDR could help mitigate TC-related socio-economic risks, particularly in East Asia.