Physical Constraints on Future Tropical Cyclone Genesis Over the Western North Pacific: A CMIP6 Multi–Model Assessment

Reliable projections of tropical cyclone genesis frequency (TCGF) under global warming remain challenging. We evaluate three genesis potential indices (χGPI, DGPI, and χMqGPI) over the western North Pacific (WNP) using 22 CMIP6 models under four SSP scenarios, supplemented by HighResMIP simulations under SSP5–8.5. All three indices broadly reproduce the observed spatial distribution and seasonal cycle of TC genesis, with χMqGPI showing the smallest bias and root‐mean‐square error in the seasonal cycle. Their future projections differ substantially: χGPI generally projects an increase, DGPI exhibits small ensemble‐mean changes with considerable inter‐model spread, whereas χMqGPI shows a decreasing tendency during the TC‐active season across all four scenarios. However, the projected χMqGPI decrease in the full 22‐model CMIP6 ensemble does not satisfy the adopted robustness criteria based on model agreement and signal‐to‐noise ratio. On the other hand, CMIP6 models with better historical spatial performance show more consistent projected decreases. A decreasing χMqGPI response is also found in the HighResMIP ensemble, where the projected change satisfies these criteria. Decomposition identifies the mid‐tropospheric moist entropy deficit and gross moisture condensation as the dominant negative contributors, reflecting changes in the coupled moisture–circulation–convection environment. These findings suggest that χMqGPI when applied to coarse‐resolution CMIP6 models provides a physically interpretable diagnostic for assessing future WNP TCGF changes, while highlighting uncertainty in multi‐model projections.