Climate change affects the global atmospheric circulation, which in turn alters precipitation and evaporation in large parts of the world and, as a result, the amount of river water that can be used locally. Previously, projections of climate impact on stream flow have usually been calculated on the basis of physical models.
New data shows that earlier models systematically underestimate how sensitively water availability reacts to certain changing climate parameters. A study of measurement data from over 9,500 hydrological catchments from all over the world shows that climate change can lead to local water crises to an even greater extent than previously expected.
“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,” said Prof. Günter Blöschl from the Institute of Hydraulic Engineering and Water Resources Management.
On a local level, it is often possible to explain very well how water availability is related to external parameters such as precipitation or temperature which is being studied at many measuring stations around the world.
“So we don’t base our analysis on physical models, but on actual measurements,” explains Günter Blöschl. “We look at how much the amount of available water changed in the past when external conditions changed. 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.”
Thus, forecasting models on the effects of climate change on water supply should 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,” said Günter Blöschl. “With the series of measurements now available, it should now be possible to adjust the physical prediction models accordingly.”
Nevertheless, the results of the research team around Günter Blöschl show that the danger of climate change on the water supply in many parts of the world may have been underestimated so far. Especially for North America, Africa and Australia, the new data predict a much higher risk of water supply crisis by 2050 than previously assumed.
https://phys.org/news/2023-02-crises-due-climate-severe-previously.html