Three-way circulation-soil moisture-temperature feedbacks amplify the most extreme mid-latitudinal heat waves.

A three-way interaction among atmospheric circulation, surface soil moisture, and temperature activates after a critical temperature threshold, adding about ∼10% to peak anomalies in the most extreme mid-latitude heat waves.

• Why it matters: Climate models underestimate how quickly the most extreme heat waves intensify, implying missing physics in how circulation and land-surface conditions jointly amplify upper-tail warming.
• What they did: Using an explainable machine-learning framework, the study quantifies interactions among circulation, soil moisture, and temperature, finding the feedback contributes on average ∼10% across ∼28% of humid mid-latitude regions.
• The result: The same interaction is systematically underestimated in CMIP6 and CESM2 Large Ensemble simulations, consistent with soils being too dry at heat-wave onset and suppressing feedback activation.

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