Present‐day irrigation mitigates heat extremes

TLDR

Irrigation is vital for global food production and influences mean climate, yet its effect on climate extremes remains largely unknown. The study uses ensemble simulations with the Community Earth System Model to evaluate how irrigation impacts climate extremes. The pronounced effect on extremes arises from irrigation timing and its strengthening of land‑atmosphere coupling. The model indicates irrigation only modestly improves near‑surface climate representation but markedly cools temperature extremes—especially the hottest day—by up to 0.78 K, with stronger subgrid‑scale effects, thereby substantially reducing exposure to heat extremes and highlighting the need to include irrigation in future climate projections.

Abstract

Abstract Irrigation is an essential practice for sustaining global food production and many regional economies. Emerging scientific evidence indicates that irrigation substantially affects mean climate conditions in different regions of the world. Yet how this practice influences climate extremes is currently unknown. Here we use ensemble simulations with the Community Earth System Model to assess the impacts of irrigation on climate extremes. An evaluation of the model performance reveals that irrigation has a small yet overall beneficial effect on the representation of present‐day near‐surface climate. While the influence of irrigation on annual mean temperatures is limited, we find a large impact on temperature extremes, with a particularly strong cooling during the hottest day of the year (−0.78 K averaged over irrigated land). The strong influence on extremes stems from the timing of irrigation and its influence on land‐atmosphere coupling strength. Together these effects result in asymmetric temperature responses, with a more pronounced cooling during hot and/or dry periods. The influence of irrigation is even more pronounced when considering subgrid‐scale model output, suggesting that local effects of land management are far more important than previously thought. Our results underline that irrigation has substantially reduced our exposure to hot temperature extremes in the past and highlight the need to account for irrigation in future climate projections.