Statement of Scientists for Future on the extreme weather events in July 2021
Human-made global warming undoubtedly contributed to the severity of the recent flooding events in Germany. A detailed attribution study on the contribution of the Climate Crisis to the flood disaster is still pending but nevertheless, the current state of research allows to clearly state that human-made global warming undoubtedly contributed to the severity of the flood event. This is the central finding of a preliminary study by climate scientists from the collective Scientists for Future (S4F).
Since the 1980s, climate models have been predicting that extreme precipitation will increase as a result of global warming. In addition, there is also increasing evidence of mounting risks due to changes in atmospheric circulation patterns. „This expected increase has since been confirmed by measured data, both globally and for Central Europe and Germany,“ says Potsdam climate researcher Stefan Rahmstorf. „The main physical reason for this is that warm air can contain more water vapor. A weakening of westerly winds probably also plays a role, making certain weather patterns last longer.„
Globally, an increase in record rainfall has been observed in recent decades, a trend that is directly linked to global warming. Specifically in Germany the floods broke a large number of climatological records. Record precipitation and water levels were measured for many affected regions. Meteorologist Özden Terli notes that „due to warming, an increase in heavy rainfall events and a decrease in days with only low precipitation can be expected.“ This redistribution toward heavy rainfall is independent of changes in the annual amount of precipitation, so even if precipitation decreases overall, heavy rainfall events may increase. Terli also points out another phenomenon: The low-pressure areas with their heavy rainfall move on slowly or not at all, so the precipitation is no longer distributed over a larger area, but falls on the same area for multiple days. Özden Terli: „A high-resolution modeling study for heavy rain in Europe shows a slowdown of weather systems and a strong increase in the frequency of quasi-stationary situations and the resulting precipitation extremes and flood risks.“ Such a stationary weather situation was a major contributor to the July 2021 floods.
Climatologist Carl-Friedrich Schleussner highlights the historical singularity of the current climate change. Never before in history has humanity been exposed to climate change that is happening at this speed — and that humans have created themselves: „The temperature values reached today are very likely the highest in 12,000 years. We are leaving the relatively stable climate of the Holocene, which made agriculture and advanced civilization possible.“ In scales of System Earth, this process is occurring at a very fast pace. This also means that we still have some uncertainty about the consequences that 1.2 ºC global warming will have for our societies.
„For the most part, we haven’t yet experienced the real extreme weather of the global warming we’ve already caused — events that would be expected only once every 20 or 50 years,” Climatologist Carl-Friedrich Schleussner
The disaster ominously shows that no one is safe from the consequences of global warming. Increased adaptation measures are urgently needed to protect against climate impacts, as the scale and severity of the event are already showing us the limitations of our adaptive capacity.
- The statement „The July 2021 floods in Germany and the climate crisis — a statement by members of Scientists for Future”