By Janet Raloff
In high-elevation snowy regions, the warming effects of greenhouse gases pale in comparison to those triggered by soot, new computer calculations show. The finding could help explain the accelerating pace of melting on the Tibetan Plateau, which holds the world’s largest reservoir of ice outside of the polar regions.
![](https://i0.wp.com/www.sciencenews.org/wp-content/uploads/2011/03/14003.jpg?resize=300%2C200&ssl=1)
Located north of the Himalayan range, the plateau’s spring meltwater feeds rivers that ultimately slake much of Asia’s thirst. In recent years, spring melting has been starting earlier, triggering downstream floods and shortening the time that irrigation water is available to farmers.
Until now, most researchers attributed the earlier runoff to global warming induced by greenhouse gases such as carbon dioxide, says Yun Qian of the Department of Energy’s Pacific Northwest National Laboratory in Richland, Wash. But Qian’s team wasn’t satisfied that carbon dioxide increases were large enough to account for the pace of the spring snowmelt’s advance.