Dirty snow melts faster than clean snow. Nowhere is this clearer than on the glaciers of the Himalayas, where scientists have recorded accelerated melting, coinciding with a greying of the glaciers.

Asia's industrial revolution is pumping out lots of smoke. Much of that smoke is billowing over the Himalayas, depositing dirty black soot on pristine white glaciers. Jing Ming, of the China National Climate Center in Beijing, and colleagues, have been using satellite data going back to 2000 to measure how dirty the glaciers have become.

Focusing on 11 representative glaciers, they discovered a clear darkening trend over the last 20 years. The findings are published in the journal Environmental Research Letters on Wednesday. Meanwhile, field studies show that this dirt becomes concentrated over time, with many years worth of dust compressed into the lower layers of the glacier, a related paper in the same journal shows.

Together with global warming this dirt is helping to melt Himalayan glaciers – dirty glaciers are less reflective and absorb more of the Sun's heat. The glaciers are the main fresh water reservoirs for much of Asia, serving more than 1bn people. Without them flash floods will become more frequent and fresh water scarce.

Pollution can be cleaned up: if Asian countries clean up their factories and cars and cut down their smoke Himalayan glaciers could eventually revert to shiny white, perhaps buying the glaciers, and all of us, some more time.

(By Kate Ravilious, Guardian.co.uk, 19/02/2012)