Earth’s climate and its water are inextricably linked—one cannot exist without the other. As the climate undergoes unprecedented, human-driven change, the global water system is changing too.
While this link is well-established, it’s difficult to predict exactly when and where extreme water shortages will occur as a result of climate change. This uncertainty inhibits decision makers’ ability to prepare for these catastrophic scenarios. A new study published Tuesday in the journal Nature Communications aims to fill that knowledge gap by estimating the timing and likelihood of extreme water scarcity events—also known as “day zero drought” events—around the world.
“Day zero basically would be the time when the region or the city runs out of water,” co-author Christian Franzke, a professor at the IBS Center for Climate Physics in Busan, South Korea, told Gizmodo.
Extreme droughts may come sooner than we thought
Day Zero Drought events result from compounded stressors on a local or regional water system, such as prolonged rainfall shortages, reduced river flow, and rising water demand. Franzke and his co-author Vecchia P. Ravinandrasana, a PhD student at the IBS Center, projected global water scarcity outcomes by applying a probabilistic framework to a large set of climate model simulations that take all these stressors into account.
Their findings suggest that by the end of the century, 74% of the world’s drought-prone regions—including those with major reservoirs—will face a high risk of severe and persistent droughts under a high emissions scenario. Nearly 35% of these regions may experience severe water scarcity by 2030.
That means 753 million people, 467 million of whom live in urban areas, could be vulnerable to extreme water scarcity under 2.7 degrees Fahrenheit (1.5 degrees Celsius) of warming above pre-industrial levels. What’s more, the amount of time between individual day zero drought events may be shorter than the events themselves, limiting recovery time and exacerbating water scarcity risks.
The findings indicate that water stress could become particularly severe in the western U.S., the Mediterranean, northern Africa, southern Africa, India, northern China, and southern Australia as demand rapidly outpaces supply.
Franzke emphasizes that these are projections, not predictions. Modeling can only tell us so much about future climatic changes and their consequences. Still, “We were surprised by how soon this may actually start to occur,” he said.
How decision-makers can use this data
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