In the late 1980s, a sudden climate regime shift (CRS) occurred throughout the Northern Hemisphere that affected both marine and inland waters. In Switzerland, rivers and lakes underwent an abrupt warming. A month-by-month comparison of water temperatures before and after the late 1980s CRS shows seasonal differences in the magnitude of the warming, which was stronger in winter, spring, and summer than in autumn. In lakes, the magnitude of the increase and the abruptness of the change diminished with increasing depth. Surface temperatures showed the most consistent abrupt warming. Hypolimnetic temperatures also increased, but the change was gradual in 3 of the 4 lakes studied. The abrupt warming in the late 1980s contributed substantially to the overall increase in temperature that has occurred in water bodies in Switzerland over the last few decades
