The rapid melting of glaciers in the Himalayas threatens the water supply of more than a billion people.
Himalayan glaciers, which supply drinking water to more than a billion people, may be threatened not only by warming from greenhouse gases, but also by soot generated far below on the plains of India, Pakistan, Nepal and Bangladesh.
Researchers believe that high levels of soot over the vast plains to the south and west of the Himalayas may be speeding the melting of glaciers in two ways.
The first involves changes in weather. According to the researchers' models, beginning each year in April, high soot levels in the atmosphere absorb sunlight, warming the air.
As the monsoon season starts in May, the warmed air draws in extra moisture and pulls it over the Tibetan Plateau. This process drops increasing amounts of rain on the glaciers, according to the models, speeding their melt.
As the glaciers thaw, the dark ground beneath the snow absorbs more heat, which also encourages the melting effect.