At the beginning of the project, the authors observed changes in lakes around the world: temperatures are rising and seasonal ice cover is shorter. However, the role of climate change in these trends had not yet been demonstrated.
"In other words, we had to rule out the possibility that these changes were caused by the natural variability of the climate system," says fellow VUB researcher and study co-author Vanderkelen.
The team therefore developed multiple computer simulations with models of lakes on a global scale, on which they then ran a series of climate models. Once the team had built up this database, they applied a methodology described by the Intergovernmental Panel on Climate Change (IPCC). After determining the historical impact of climate change on lakes, they also analysed various future climate scenarios.
The results show that it is highly unlikely that the trends in lake temperatures and ice cover in recent decades can be explained solely by natural climate variability. Moreover, the researchers found clear similarities between the observed changes in lakes and model simulations of lakes in a climate influenced by greenhouse gas emissions.
"This is very convincing evidence that climate change caused by humans has already impacted lakes," says Grant. Projections of lake temperatures and ice cover loss unanimously indicate increasing trends for the future. 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 revealed 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 great importance of the Paris Agreement to protect the health of lakes around the world," says Wim Thiery, VUB climate expert and senior author of the study. "If we manage to drastically reduce our emissions in the coming decades, we can still avoid the worst consequences for lakes worldwide."
The paper 'Attribution of global lake systems change to anthropogenic forcing' has been published in Nature Geoscience on Monday October 18 - https://www.nature.com/articles/s41561-021-00833-x