Climate change over the last 40 years has increased the temperature of lakes around the world by half a degree
- An international team coordinated by the Catalan Institute for Water Research (ICRA) shows how the temperature and ice in lakes has changed over the last forty years, and establishes that only climate change can explain it.
- It is estimated that, by the end of the 21st century, the average warming of lakes could increase by up to 4.0 °C and the duration of the ice cover will be 46 days shorter.
- The relevance of this study is that for the first time we can rule out that these observed changes are caused by the natural variability of the climate system," explains Rafael Marcé, ICRA researcher and coordinator of the international network that has made this work possible.
The international research, led by the BCLIMATE research group of the Vrije Universiteit Brussel (VUB), shows an average increase of 0.5 ºC in the average surface water temperature of the lakes over the last 40 years, and a reduction in the ice-covered period of 10 days, as the ice sheet forms later and melts earlier. These global changes in temperature and ice cover are not due to natural climate variability and can only be explained by greenhouse gas emissions since the Industrial Revolution. "These physical properties are fundamental to lake ecosystems," says Luke Grant, VUB researcher and lead author of the study. "Many species are already feeling these changes, and as impacts continue to increase in the future, we risk severely damaging ecosystems, including water quality and populations of native fish species."
The results of the research, which has been published in Nature Geoscience, also predict future developments under different warming scenarios. By the end of the 21st century, in a low-emissions scenario, average lake warming is estimated to stabilise at 1.5 °C above pre-industrial levels and the duration of the ice sheet will be 14 days shorter. In a high-emissions world, these changes could lead to a 4.0°C increase and 46 fewer ice days.
"The fact that lakes are warming has been clear to us for a decade or more. The relevance of this study is that for the first time we can rule out that these observed changes are caused by the natural variability of the climate system," explains Rafael Marcé, a researcher at the University of Barcelona. explains Rafael Marcé, researcher at the Catalan Institute for Water Research (ICRA) and coordinator of the international network that has made this work possible. To do so, the team used a global climate change impact simulation network (ISIMIP) to run millions of computer simulations, which simulated temperature and ice in 17,000 lakes around the world under historical and future climate conditions. "The comparison of historical simulations with lake data over the last 40 years is compelling: lakes are warming and have less and less ice, and this cannot be explained other than by including human-induced climate change in the simulations," explains Rafael Marcé.
Projections of lake temperatures and ice cover indicate increasing trends for the future in all models. For every 1 °C increase in global air temperature, lakes are estimated to warm by 0.9 °C and lose 9.7 days of ice cover. In addition, the analysis reveals significant differences in the impact on lakes at the end of the century, depending on the measures taken by humans to combat climate change. "Our results underline the importance of the Paris Agreement in protecting the health of lakes around the world," explains Wim Thiery, climate expert at VUB and coordinator of the study. "If we manage to drastically reduce our emissions in the coming decades, we can still avoid the worst consequences for lakes around the world."
Grant, L., I. Vanderkelen, L. Gudmundsson, Z. Tan, M. Perroud, V. Stepanenko, A. Debolskiy, B. Droppers, A. Janssen, I.R. Woolway, M. Choulga, G. Balsamo, G. Kirillin, J. Schewe, F. Zhao, I. Vega del Valle, M. Golub, D. Pierson, R. Marcé, S. Seneviratne, and W. Thiery. 2021. Attribution of global lake systems change to anthropogenic forcing. Nature Geoscience, https://www.nature.com/articles/s41561-021-00833-x.
Additional information: WATExR project: https://watexr.eu/
Photo: Lake Geneva, Switzerland, one of the many lakes where increases in water temperature have been detected in recent decades. © Rafael Marcé