Physical Constraints on Future Tibetan Plateau Summer Precipitation: Emergent Relationships and Pareto Optimal Ensembles

ABSTRACT

Precipitation projections over the Tibetan Plateau (TP) are critical for regional water resources adaptation and ecological security; however, inter‐model uncertainty substantially constrains their reliability. Based on the Phase 6 of the Coupled Model Intercomparison Project (CMIP6) multi‐model ensemble, this study employs emergent constraint schemes grounded in physical relationships and Pareto optimal ensemble selection schemes based on model screening, aiming to reduce uncertainties in mid‐to‐late 21st century (2051–2100) summer precipitation projections over the TP. The results indicate that inter‐model uncertainty is the dominant source limiting projection robustness, maintaining its leading role throughout the 21st century with a peak contribution during 2040–2050 and remaining significant in the mid‐to‐long term (69%). Emergent constraint relationships of TP summer precipitation with historical global warming trends and with Indo‐Pacific Warm Pool Sea Surface Temperature (SST) are both statistically significant and effectively reduce future projection uncertainty. Using Pareto optimal multi‐objective screening, bivariate constraint schemes pairing summer precipitation with the global warming trend and with Indo‐Pacific Warm Pool SST are found to outperform emergent constraints in compressing uncertainty. Specifically, they reduce uncertainty by more than 30% under the low emission scenario and can reach up to 40% under the medium and high emission scenarios. After constraint application, the projected mid‐to‐long term summer mean precipitation over the plateau converges to 5.77–7.22 mm day ⁻¹ , effectively correcting the systematic overestimation present in the original ensemble. Highly consistent spatial patterns across methods enhance projection robustness. Constrained increments show a south to north decreasing gradient, consistently suppressing southern overestimation. Most importantly, the optimal scheme reveals negative precipitation anomalies over the northwestern plateau, suggesting that this region may face a localised aridification risk.