Annual maximum lake surface temperature influences ecosystem structure and function and, in particular, the rates of metabolic activities, species survival and biogeography. Here, we evaluated 50 years of observational data, from 1966 to 2015, for ten European lakes to quantify changes in the annual maximum surface temperature and the duration above a potentially critical temperature of 20 °C. Our results show that annual maximum lake surface temperature has increased at an average rate of +0.58 °C decade⁻¹ (95% confidence interval 0.18), which is similar to the observed increase in annual maximum air temperature of +0.42 °C decade⁻¹ (95% confidence interval 0.28) over the same period. Increments in lake maximum temperature among the ten lakes range from +0.1 in the west to +1.9 °C decade⁻¹ in the east. Absolute maximum lake surface water temperatures were reached in Wörthersee, 27.5 °C, and Neusiedler See, 31.7 °C. Periods exceeding a critical temperature of 20 °C each year became two to six times longer than the respective average (6 to 93). The depth at which water temperature exceeded 20 °C increased from less than 1 to more than 6 m in Mondsee, Austria, over the 50 years studied. As a consequence, the habitable environment became increasingly restricted for many organisms that are adapted to historic conditions.

每年的最高湖面温度会影响生态系统的结构和功能，特别是影响代谢活动，物种生存和生物地理学的速度。在这里，我们评估了从1966年到2015年的10年欧洲湖泊50年的观测数据，以量化年度最高表面温度的变化以及超过20°C的潜在临界温度的持续时间。我们的结果表明，每年的最高湖面温度以+0.58°C十进制^-1（95％置信区间0.18）的平均速率增加，这与观测到的年度最高空气温度+0.42°C十进制的增加率相似^{- 1个}（95％置信区间0.28）。十个湖泊中，湖泊最高温度的升高幅度从西部的+0.1到东部的+1.9°C十年^-1。沃特湖（Wörthersee）最高绝对温度为27.5°C，诺伊西德勒湖（Neusiedler See）最高绝对温度为31.7°C。每年超过临界温度20°C的时期比各自平均值（6至93）长2至6倍。在研究的50年中，奥地利Mondsee的水温超过20°C的深度从不到1 m增加到6 m以上。结果，对于许多适应历史条件的生物来说，可居住的环境越来越受到限制。