Lake ecosystems, and the organisms that live within them, are vulnerable to temperature change^1,2,3,4,5, including the increased occurrence of thermal extremes⁶. However, very little is known about lake heatwaves—periods of extreme warm lake surface water temperature—and how they may change under global warming. Here we use satellite observations and a numerical model to investigate changes in lake heatwaves for hundreds of lakes worldwide from 1901 to 2099. We show that lake heatwaves will become hotter and longer by the end of the twenty-first century. For the high-greenhouse-gas-emission scenario (Representative Concentration Pathway (RCP) 8.5), the average intensity of lake heatwaves, defined relative to the historical period (1970 to 1999), will increase from 3.7 ± 0.1 to 5.4 ± 0.8 degrees Celsius and their average duration will increase dramatically from 7.7 ± 0.4 to 95.5 ± 35.3 days. In the low-greenhouse-gas-emission RCP 2.6 scenario, heatwave intensity and duration will increase to 4.0 ± 0.2 degrees Celsius and 27.0 ± 7.6 days, respectively. Surface heatwaves are longer-lasting but less intense in deeper lakes (up to 60 metres deep) than in shallower lakes during both historic and future periods. As lakes warm during the twenty-first century^7,8, their heatwaves will begin to extend across multiple seasons, with some lakes reaching a permanent heatwave state. Lake heatwaves are likely to exacerbate the adverse effects of long-term warming in lakes and exert widespread influence on their physical structure and chemical properties. Lake heatwaves could alter species composition by pushing aquatic species and ecosystems to the limits of their resilience. This in turn could threaten lake biodiversity⁹ and the key ecological and economic benefits that lakes provide to society.

湖泊生态系统以及生活在其中的生物容易受到温度变化的影响^1,2,3,4,5，包括极端温度事件的增加⁶. 然而，人们对湖泊热浪——极端温暖的湖面水温时期——以及它们在全球变暖下可能发生的变化知之甚少。在这里，我们使用卫星观测和数值模型来研究 1901 年至 2099 年全球数百个湖泊的湖泊热浪变化。我们表明，到 21 世纪末，湖泊热浪将变得更热、持续时间更长。对于高温室气体排放情景（代表性浓度路径 (RCP) 8.5），相对于历史时期（1970 年至 1999 年）定义的湖泊热浪平均强度将从 3.7 ± 0.1 度增加到 5.4 ± 0.8 度摄氏度及其平均持续时间将从 7.7 ± 0.4 天急剧增加到 95.5 ± 35.3 天。在低温室气体排放 RCP 2.6 情景中，热浪强度和持续时间将增加到 4.0 ± 0。分别为 2 摄氏度和 27.0 ± 7.6 天。在历史和未来时期，与浅湖相比，深湖（深达 60 米）的地表热浪持续时间更长，但强度更低。随着二十一世纪湖泊变暖^7,8，他们的热浪将开始跨越多个季节，一些湖泊达到永久热浪状态。湖泊热浪可能加剧湖泊长期变暖的不利影响，对其物理结构和化学性质产生广泛影响。湖泊热浪可以通过将水生物种和生态系统推向其恢复力的极限来改变物种组成。这反过来又可能威胁到湖泊生物多样性⁹以及湖泊为社会提供的重要生态和经济效益。