Swiss climate researchers predict future with pebbles

The researchers focused on the prehistoric Pyrenees, which were also affected by severe flooding in 2013. Pictured here is the River Esera bursting its banks in Huesca, Spain. EPA

Over 50 million years ago, global warming caused extreme flooding and landscape disruption, say researchers from the University of Geneva (UNIGE). They describe the lessons as worrying for the future. 

A study published in the latest Scientific ReportsExternal link shows that the Earth experienced an “exceptional episode” of global warming 56 million years ago, with the average temperature increasing by 5-8 degrees Celcius – over a period of 10,000-20,000 years – a “very short time on a geological scale”. 

Based on the analysis of sediments from the southern slope of the Pyrenees, the UNIGEExternal link researchers measured the impact of this warming on river floods and the surrounding landscapes. They concluded that the consequences were severe, with green landscapes perhaps turning into arid and pebbly plains. 

“The Spanish Pyrenees offer sediments that allow us to observe the ancient river channels and to determine their size,” explained UNIGE in a press release published on Thursday. “Thanks to the direct relationship between the size of the pebbles and the slope of the rivers, researchers were thus able to calculate their flow velocity and discharge. They have therefore unveiled the whole history of these rivers, and that of the spectacular changes that have affected them.” 

+ Switzerland experienced the flood of the century in 2005

Study leader Sébastien Castelltort, professor at UNIGE’s Department of Earth Sciences, cites an “obvious analogy” with the current global warming. “There are lessons to be learned from this event, even more so as the rise in temperatures we are currently witnessing seems to be much faster.” 

The study, supported by the Swiss National Science FoundationExternal link, was done in collaboration with researchers from the universities of Lausanne, Utrecht, Western Washington and Austin.