A report published by the UN’s Environment Program warns that melting glaciers in Asia’s mountains could affect an estimated 40% of the world’s population, who rely on ice melt for irrigation and drinking water. Global warming could disrupt ecosystems around the world, with devastating economic and environmental consequences for hundreds of millions of people.

The study, issued at the UN Global Outlook for Ice and Snow in Tromso, Norway, said rising temperatures were already thawing permafrost in Siberia, releasing methane, a potent greenhouse gas.

If emissions continue unabated, the Antarctic and Greenland ice sheets, which hold almost all the planet’s freshwater ice, are likely to become unstable.

Without measures to mitigate sea-level rise, an estimated 145 million people would be exposed to the risk of flooding.