Climate change may have altered river flow worldwide

There is no doubt that human-induced climate change is profoundly affecting various Earth systems, including the global water cycle. For some processes, such as river flow and hydrological extremes, the potential role of climate change is not as well understood. 

In a new study published by AAAS, experts have found evidence that the far-reaching impacts of climate change have altered river flows at a global scale. 

A team of researchers led by Lukas Gudmundsson analyzed thousands of time lapses of low, mean, and high river flows from 7,250 observatories worldwide. The data was collected over the course of 50 years from 1971 to 2010. 

According to the experts, the historical observations revealed recent, spatially complex global hydrological trends. They found that rivers in some regions are drying up and flowing less, others are growing wetter and have more water. 

Using a technique called climate change detection and attribution, the study authors compared the observational data to Earth system model simulations of the terrestrial water cycle. 

The results showed that patterns in global river flow are only consistent with model predictions that account for the effects of radiative forcing from anthropogenic climate change. 

The simulated effects of water and land management alone are not enough to explain the recent patterns, said the researchers. 

The findings suggest that climate change is the main driver of the shifting trends observed in river flows globally. 

In a review of the study, Julia Hall and Rui Perdigão argue that while the attribution to climate change is logical and likely in terms of process understanding of climate dynamics, the evidence provided is “circumstantial.” In other words, there were additional processes that could have contributed to the observed trends that were not accounted for in the projections. 

“To improve the explanatory power of such important studies and to generate more confidence in such attribution statements, we need to move beyond these first-order assessments that involve simple proof of consistency and inconsistency when investigating the effects of climate change,” wrote Hall and Perdigão.

The study is published in the journal Science.

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By Chrissy Sexton, Earth.com Staff Writer