Globally observed trends in mean and extreme river flow attributed to climate change
Study key findings & significance
- Climate change - not water and land management - plays a crucial role in changes in rivers and streams at the global level.
- Researchers analyzed data from 7,250 measuring stations worldwide and found systematic change in river flow between 1971 and 2010.
- They compared the observations with simulations from climate models calculated once with man-made greenhouse gases and once without.
- Before the study, researchers had not yet investigated how river flow has changed worldwide in recent years using direct observations. Similarly, researchers had not clarified the question of whether or not globally visible changes are attributable to climate change or to water and land management.
Changes in water and land management are evidently not the cause of global changes in rivers.
Lukas Gudmundsson, lead author and professor at the Institute for Atmospheric and Climate Science at ETH Zurich
Anthropogenic climate change is expected to affect global river flow. Here, we analyze time series of low, mean, and high river flows from 7250 observatories around the world covering the years 1971 to 2010. We identify spatially complex trend patterns, where some regions are drying and others are wetting consistently across low, mean, and high flows. Trends computed from state-of-the-art model simulations are consistent with the observations only if radiative forcing that accounts for anthropogenic climate change is considered. Simulated effects of water and land management do not suffice to reproduce the observed trend pattern. Thus, the analysis provides clear evidence for the role of externally forced climate change as a causal driver of recent trends in mean and extreme river flow at the global scale.