Abstract
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.
Highlights
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
Detection and attribution studies have shown that observed changes in atmospheric variables such as precipitation [4, 5] and water vapor [6] are consistent with model simulations that account for historical anthropogenic climate change (ACC), evidence for a human fingerprint on past changes in river flow and hydrological extremes is still lacking at the global scale
The results show that the combined effect of historical radiative forcing and historical water and land management (HWLM) is detected in observed trend patterns of low, mean, and high river flow
Summary
Observed trends in mean and extreme river flow attributed to climate change Gudmundsson, Lukas; Boulange, Julien; Do, Hong X.; Gosling, Simon N.; Grillakis, Manolis G.; Koutroulis, Aristeidis G.; Leonard, Michael; Liu, Junguo; Müller Schmied, Hannes; Papadimitriou, Lamprini; Pokhrel, Yadu; Seneviratne, Sonia I.; Satoh, Yusuke; Thiery, Wim; Westra, Seth; Zhang, Xuebin; Zhao, Fang. The results show that the combined effect of historical radiative forcing and HWLM is detected in observed trend patterns of low, mean, and high river flow. The ISIMIP2b ensemble allows HWLM to be accounted for in a climate change detection and attribution setup for the first time, the fact that no separate simulations with either anthropogenic or historical natural forcing are available hinders an unambiguous attribution of the observed trend pattern to ACC. Combining the evidence of these findings with the results of the presented analysis (Figs. 1 and 2) supports the conclusion that it is likely that ACC is contributing to the global pattern of trends in low, mean, and high river flow
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