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Climate change interferes with Earth’s water cycle more than previously thought

It is well-established that climate change does interfere with the planet’s water cycle, but new studies show we underestimated the impact.

14 dead as Ida brings flash flooding to New York area
Floodwater surrounds vehicles following heavy rain on an expressway in Brooklyn, New York early on September 2, 2021, as flash flooding and record-breaking rainfall brought by the remnants of Storm Ida swept through the area - Copyright POOL/AFP KIM Min-Hee
Floodwater surrounds vehicles following heavy rain on an expressway in Brooklyn, New York early on September 2, 2021, as flash flooding and record-breaking rainfall brought by the remnants of Storm Ida swept through the area - Copyright POOL/AFP KIM Min-Hee

It is well-established that climate change does interfere with the planet’s water cycle, but new studies show we underestimated the impact.

Climate change alters the global atmospheric circulation, which in turn alters precipitation and evaporation in large parts of the world.

For example, streamflow from a river channel is formed by run-off aggregated from the upstream contribution area (or catchment), in turn, providing an essential freshwater resource for sustaining humans and ecosystems

However, new data analyses conducted under the leadership of Prof. Günter Blöschl (TU Wien, Vienna) indicate that previous models systematically underestimate how sensitive water availability reacts to certain changing climate parameters.

Observation of stream flow from 9,505 catchments across the globe shows that climate change can lead to local water crises to an even greater extent than previously expected.

The new study found that in the near future (2021–2050) global streamflow may be lower than predicted by Earth System Models, particularly in Africa, Australia, and North America. The results have now been published in the scientific journal Nature Water.

“In the climatology community, the effects of climate change on the atmosphere are very well understood. However, their local consequences on rivers and the availability of water falls into the field of hydrology,” explains Prof. Günter Blöschl from the Institute of Hydraulic Engineering and Water Resources Management at TU Wien, according to Science Daily.

The water cycle is often taught as a simple circular cycle of evaporation, condensation, and precipitation. Although this can be a useful model, the reality is much more complicated. (Image credit: Dennis Cain/NWS)

As Professor Blöschl explains, water availability is related to external parameters such as precipitation or temperature. And locally, around the world, measuring stations do provide information related to various parameters, but global conclusions cannot be drawn from such individual observations.

“How the water balance depends on external parameters varies from place to place; local vegetation also plays a very important role here,” says Günter Blöschl, reports Phys.Org. It is difficult to develop a simple physical model that can be used to calculate these interrelationships at all places in the world with precision.

To address the problem, Blöschl collaborated with colleagues from China, Australia, the USA, and Saudi Arabia to build up and analyze a large database of streamflow observations from all over the world, some going back several decades.

“So we don’t base our analysis on physical models, but on actual measurements,” Günter Blöschl emphasizes. “We look at how much the amount of available water changed in the past when external conditions change. In this way, we can find out how sensitively changes in climate parameters are related to a change in local water availability. And this allows us to make predictions for a future, warmer climate.”

As it turns out, the connection between precipitation and the amount of water in the rivers is much more sensitive than was previously thought — and thus much more sensitive than is assumed in the models currently used to predict climate change.

Forecasting models of the effects of climate change on water supply should therefore be fundamentally revised. “Up to now, runoff measurements have usually not been included at all in the models, such as those currently reported by the IPCC,” says Blöschl. “With the series of measurements now available, it should now be possible to adjust the physical prediction models accordingly.”

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We are deeply saddened to announce the passing of our dear friend Karen Graham, who served as Editor-at-Large at Digital Journal. She was 78 years old. Karen's view of what is happening in our world was colored by her love of history and how the past influences events taking place today. Her belief in humankind's part in the care of the planet and our environment has led her to focus on the need for action in dealing with climate change. It was said by Geoffrey C. Ward, "Journalism is merely history's first draft." Everyone who writes about what is happening today is indeed, writing a small part of our history.

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