Nuclear Winter Could Sever Urban Water Access Across the Northern Hemisphere

The continuous functioning of the underground water supply networks is essential for many aspects of modern civilization. Therefore, it is essential to keep such critical infrastructure safe from disasters. However, existing risk assessment studies often assume relatively stable climate conditions. Abrupt sunlight reduction scenarios, such as those caused by a nuclear war, a large volcanic eruption, or an asteroid impact, could cool the planet by up to 10°C and thus frost-damage water pipes. This study investigates such vulnerability of the global underground water supply network in urban areas, in a nuclear winter – one such abrupt climate shift resulting from a nuclear war. We use climate modeling data simulating a nuclear exchange between Russia and the United States of America, in combination with predictions of the network location and density derived from nighttime light and artificial impervious surface data. By considering an increase in maximum frost depth under nuclear winter conditions, we identify areas where such networks are most vulnerable to disruption, and predict the length of the potentially affected pipelines using population-size-based and street-network-length-based models. As estimated, a total of ~5–9 million kilometers of this critical infrastructure in 92 countries is at risk of freezing, potentially impacting the primary water source of over 2 billion individuals. Our findings highlight the need to expand the scope of climate resilience assessments in water risk research to include a broader range of climate scenarios, including sudden cold shifts.