Marine heatwaves: definition duel heats up

Changing the commonly used definition of a marine heatwave from a fixed to a shifting temperature baseline (D. J. Amaya et al. Nature 616, 29–32; 2023) would be inconsistent with current trends and confuse communications relating to extreme conditions.

A fixed-baseline definition reflects the increasingly frequent and devastating biological impacts of marine heatwaves (K. E. Smith et al. Ann. Rev. Mar. Sci. 15, 119–145; 2023). A shifting baseline artificially decouples processes that act on different timescales, so it cannot reveal the increasing risks caused by climate change. This could create the false impression that temperature extremes and their associated impacts will remain almost unchanged.