Evaluating Divergent Evapotranspiration Feedbacks to Warming Across Water- and Energy-Limited Regimes

Land–atmosphere coupling is a central driver of climate variability and extremes, yet Earth System Models (ESMs) struggle to capture the complex interplay between hydrology, vegetation, and surface energy fluxes. In particular, the evapotranspiration–temperature (ET–T) feedback—a key mechanism linking soil moisture, vegetation water use, and near-surface climate—is poorly constrained, limiting confidence in projections of heat extremes and ecosystem stress. Here, we first assess ET–T feedback across a suite of post-CMIP6 ESMs for the historical period (1980–2014) as compared with available GLEAM observations; thereafter the ET-T feedback is investigated in a set of future idealized warming scenarios spanning multiple global temperature targets. To identify the physical and ecohydrological regimes controlling feedback strength, we apply the Ecosystem Limitation Index (ELI), which distinguishes energy-limited from water-limited conditions. Our results reveal a strong negative ET–T feedback in energy-limited regions, where evapotranspiration efficiently cools the surface and stabilizes temperature. In contrast, the feedback reverses in water-limited and transitional regions: here, worsening soil-moisture deficits suppress evaporation and reduce evaporative cooling, thereby amplifying surface warming. Comparison with GLEAM observations highlights regions where models succeed and fail in capturing these feedbacks, particularly in semi-arid ecosystems where land–atmosphere coupling is strongest. Future warming scenarios indicate an expansion of water-limited regimes, weakening negative ET–T feedbacks and reducing the ability of land surface to buffer temperature variability. This shift implies an increased risk of persistent heat extremes, stronger land-surface amplification of warming, and eco-hydrological transitions in sensitive regions. The findings of this study suggest priorities for next-generation ESMs: better representation of soil moisture dynamics, vegetation water-use strategies, and hydrological constraints.