A study found that global warming could trigger multi-year droughts and bring about a worldwide water shortage crisis. It means a day could come when no water comes out of the tap at all, causing severe damage to daily life and industry across the board.
Researchers with the Institute for Basic Science (IBS) Climate Physics Research Center announced in the international journal "Nature Communications" on the 24th that global warming will greatly increase the risk of extreme multi-year droughts in the coming decades. The researchers noted that the impact could go beyond simple water scarcity to cause serious damage across daily life, agriculture, and industry in both cities and rural areas.
Using the latest climate model simulations, the researchers calculated the point at which water demand in a given region exceeds water supply from precipitation, rivers, and reservoirs. They named this point "Day Zero drought (DZD)." As the name suggests, it means the day when no water comes out even if you turn on the tap. In fact, major cities such as Cape Town, South Africa, in 2018 and Chennai, India, in 2019 faced the risk of water supply shutdowns.
The study found that regions relying solely on surface water are extremely vulnerable due to the combined effects of reduced precipitation and river flow caused by climate change, along with increased water use. In particular, the Mediterranean, southern Africa, and parts of North America were identified as major DZD risk areas. Groundwater was excluded from this analysis. If groundwater is also depleted, the situation could become far more serious.
The researchers projected that within the next 15 years, 35% of vulnerable regions worldwide could face DZD, and by the end of the century about 750 million people will be exposed to water shortage risks. Of these, approximately 470 million will be urban residents and about 290 million will be rural populations. Urban water shortages are expected to be severe in the Mediterranean, while livelihoods in parts of Africa and Asia are projected to face acute crises.
The study shows that water supply systems for urban drinking water and agriculture are becoming increasingly vulnerable, and that DZD frequency will surge much faster over the coming decades than previously expected.
Doctoral researcher Vecchia Ravinandrasana said, "These results show that global warming is triggering and accelerating DZD conditions worldwide," adding, "Even if the 1.5-degree temperature rise limit is achieved, hundreds of millions will face unprecedented water shortages." The Paris Agreement, adopted in Paris, France, in 2015, set a goal of limiting the rise in the global average temperature, compared with the preindustrial level, to within 1.5 degrees Celsius.
Christian Franzke, a professor at the Pusan National University Institute of Climate Physics, warned, "As water resources stress intensifies, 14% of major reservoirs could already be depleted during the first Day Zero event," adding, "In that case, the very basis of agriculture and livelihoods could collapse."
References
Nature Communications (2025), DOI: https://doi.org/10.1038/s41467-025-63784-6