Increasingly intense floods and droughts are a “distress signal” of what is to come as climate change makes the planet’s water cycle ever more unpredictable, the United Nations warned Monday.

Last year the world’s rivers were their driest for more than 30 years, glaciers suffered their largest loss of ice mass in half a century and there was also a “significant” number of floods, the UN’s World Meteorological Organization said in a report.

“Water is the canary in the coalmine of climate change,” WMO Secretary-General Celeste Saulo said in a statement accompanying the State of Global Water Resources report.

“We receive distress signals in the form of increasingly extreme rainfall, floods and droughts which wreak a heavy toll on lives, ecosystems and economies,” she said.

Saulo said the heating up of the Earth’s atmosphere had made the water cycle "more erratic and unpredictable.