There is growing evidence indicating that variability and extremes in conditions in the marine environment are as (or more) important as changes in the mean for determining threats to biodiversity, impacts on ecosystem services, and consequences for human systems (1⇓⇓–4). With respect to ocean temperature, long-term persistent warming has been accompanied by an increased frequency of discrete periods of extreme regional ocean warming (marine heatwaves) (5). This poses a threat to biodiversity and ecosystem services, including impacts on foundation species (corals, seagrasses, and kelps) (1, 4). The potential of human and natural systems to adapt to such changes remains unclear. In PNAS, Pershing et al. (6) show that an increasing frequency of extreme heat events—or “surprises”—is challenging autonomous modes of adaptation that rely on historical experience. The authors contrast reactive adaptation that is guided by experiences of past events with proactive adaptation based on forward-looking decision making. They use ocean ecosystems as a case study and, based on mathematical models, consider how temperature trends and the frequency of surprise (high) temperature events could impact natural and human communities under different adaptation strategies. Pershing et al. (6) define a temperature surprise as an annual mean temperature that is 2 SDs above the mean, where the … [↵][1]1To whom correspondence may be addressed. Email: geir.ottersen{at}ibv.uio.no. [1]: #xref-corresp-1-1