Scientists Himalayan ice warning

The Himalayan glaciers formed some 70 million years ago. Photo / 123RF

Vast mountain glaciers helping provide water, irrigation and power for up to two billion people are expected to shrink by at least a third as temperatures heat up this century, scientists have warned.

The ice caps of the Hindu Kush Himalaya region feed some of the world's mightiest rivers and have been likened to the "water tower of Asia". But global warming is on course to thaw swathes of their cover even if the world hits ambitious targets to limit temperature rises, according to a new report on their future.

Forecasts of the impact of climate change have focused on islands and coastal zones, overlooking the effect on an area known as a "third pole" because of the amount of ice it holds.

"This is the climate crisis you haven't heard of," said Philippus Wester, who led the report.

The glacier region straddling Afghanistan, Bangladesh, Bhutan, China, India, Myanmar, Nepal and Pakistan will shrink by two-thirds if no progress is made reining in emissions, he predicted.

"Global warming is on track to transform the frigid, glacier-covered mountain peaks of the HKH cutting across eight countries to bare rocks in a little less than a century," said Wester of the International Centre for Integrated Mountain Development (ICIMOD).

The report, by 210 authors, said 36 per cent of the ice in the region will melt by 2100 even if governments hit the most ambitious 2015 Paris climate agreement targets to limit temperature rises to one-and-a-half degrees.

If no action is taken to reduce emission of green house gases, two-thirds of the ice will go.

Glaciers have thinned and retreated across most parts of the region since the 1970s. Ice in the Hindu Kush Himalaya region would push up sea levels by 1.5m if it all melted, Eklabya Sharma, deputy director general of ICIMOD, said.

The Himalayan glaciers formed some 70 million years ago.

Effects from their melting will range from worsened air pollution to more extreme weather. Changed river flows will throw urban water systems and food and energy production off-kilter, the study warned.

The 2015 Paris Agreement seeks to keep a global temperature rises this century well below 2C above pre-industrial levels, and aim to keep them to 1.5 degrees if possible.