Hundreds of millions of livelihoods will be affected by declining snow and ice cover as a result of global warming, a UN report has warned.

The study warns of a range of threats that could destabilise ecosystems around the world, with potentially devastating consequences for hundreds of millions of people.

Melting glaciers in Asia's mountains could affect an estimated 40% of the world's population, who rely on ice melt for crop irrigation and drinking water.

It added that rising temperatures were already resulting in the thawing of permafrost in places such as Siberia. This was leading to the release into the atmosphere of methane, a potent greenhouse gas.

The fate of the Antarctic and Greenland ice sheets, which hold almost all of the planet's freshwater ice, needed to be better understood, the UN publication urged.
It said that if emissions of greenhouse gases continued unabated, the massive ice sheets were likely to become unstable as the world continued to warm.

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