Soot gets everywhere. Even into the world’s highest mountains

THE Himalayas and the adjacent Tibetan plateau are sometimes referred to as the Earth’s third pole, because of the amount of ice they host. They are also known as Asia’s water tower. Their glaciers feed the continent’s largest rivers—and those, in turn, sustain some 1.5 billion people. Many studies suggest, though, that the Himalayan glaciers have been shrinking over the past few decades. This has usually been attributed to rising air temperatures, but climate researchers have now come to realise that tiny airborne particles of soot and dust are also to blame. Being dark, they absorb sunlight. And that warms their surroundings.

Near cities, and in regions like South-East Asia, where people are clearing vegetation by burning it, soot is expected. But as Angela Marinoni of the Institute of Atmospheric Sciences and Climate in Bologna explained to an audience at the 2nd Third Pole Environment Workshop in Kathmandu on October 27th, the high Himalayas are also under an onslaught from this sort of pollution. Even at altitudes above 5,000 metres (16,400 feet), soot is widespread. And when it lands on glaciers it accelerates their melting. …