Global warming could bring water shortages to one in six people around the world, scientists have warned.
They reckon the worst hit areas will be places that depend on slowly melting ice and snow to top up their water supplies over dry summers.
Because higher temperatures would bring less snow and more rain, the ice would soon run out, bringing water shortages.
They warn that even developed countries like America could be affected by droughts within 20 years.
Not enough snow
The scientists say that although the same amount of water would fall, more of it would be rain.
That means it would flow away quickly in rivers, rather than being slowly released by melting snow and ice.
The reservoirs and other water stores that we have at the moment wouldn't be able to hold all the water that fell as rain in winter, leaving a shortage in summer.