ACC News Brief
Climate Science Contiguous United States ecosystems
During heatwaves, soil evaporation carried more of the surface-cooling load
What happened
Researchers analyzed 268 heatwaves recorded from 2019 through 2021 at 32 National Ecological Observatory Network flux sites. Their ensemble of four partitioning methods estimated that plants' transpiration share of evapotranspiration fell during heatwaves, while variation in soil evaporation explained more of the observed surface-cooling differences; in especially long events, soil evaporation eventually collapsed as moisture was depleted.
Why it matters
Climate and land models need to represent how heat changes the sources of evapotranspiration, because cooling can weaken as soils dry. The study does not show that adding irrigation is a universal heat solution: water scarcity, ecosystem needs, crop choice, and local conditions remain decisive.
What to watch
- Direct field measurements that can test evapotranspiration partitioning across more climates, ecosystems, and longer heatwaves.
- How land-surface and crop models represent soil-moisture depletion, plant stress, and cooling without encouraging unsustainable water use.
Sources & evidence
- Shifts in Evapotranspiration Components During Heatwaves Alter Surface CoolingPeer-reviewed open-access Article in Earth's Future 14, published February 14, 2026. The study evaluated 268 heatwaves lasting at least three days at 32 contiguous-U.S. NEON flux sites during 2019-2021 and used an ensemble of four high-frequency turbulence methods to partition evapotranspiration. This is OBSERVED plus ESTIMATED MECHANISM evidence: fluxes were observed, but component partitioning has no single gold-standard method, site coverage was limited, and comparative and machine-learning analyses do not establish a controlled intervention or justify irrigation without water-tradeoff analysis.
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