NEWS & EVENTS

Uncertainties in Tropical cyclones (TCs) genesis under various climate projections necessitate assessment at consistent target warming levels to better inform policy-making. Using simulations from thirteen Coupled Model Intercomparison Project Phase 6 (CMIP6) models, we investigate uncertainties in projected changes in two TC genesis potential indices: the Emanuel–Nolan GPI (ENGPI) and the dynamic GPI (DGPI), focusing on spatial patterns and seasonal cycles across multiple global warming levels (GWLs). Absolute uncertainties in both GPIs increase with GWLs, whereas relative uncertainties decline, indicating clearer signals relative to noise at higher GWLs. Spatially, the West Pacific exhibits the largest absolute uncertainties, while relative uncertainties peak in the Southern Hemisphere. Seasonally, the North Indian basin shows the greatest absolute uncertainties. Compared to inter-model uncertainties, inter-scenario uncertainties are negligible at +1°C GWL, increase substantially by +1.5°C, and stabilize between +2°C and +3°C, highlighting the relative importance of emission pathways in shaping uncertainties at intermediate GWLs, while model differences dominate at lower and higher GWLs. DGPI uncertainties are mainly driven by wind shear and vertical velocity, while ENGPI uncertainties are controlled by thermodynamic factors, which show greater inter-model spread. Compared to assessing GPIs uncertainty based on GWLs, basin on regional warming levels (RWLs) yield higher absolute and inter-scenario uncertainties but lower relative uncertainties of GPIs’ change due to amplified land and Arctic warming. This finding further suggests that GWL-based assessments may underestimate both the noise and signal of GPIs changes, which underscores the need for RWL-based approaches in climate adaptation planning.

Additional information: Miss GAO Yurong, yurong.gao@connect.hku.hk