Himalayan glaciers feed rivers and lakes across South Asia that more than a billion people depend upon for fresh water. It’s for this reason – and the fact that many have experienced rapid changes in recent decades – that scientists keep an especially watchful eye on ice in the region.
Much of the data collected to date suggests the prognosis isn’t good. As Goddard Space Flight Center atmospheric scientist William Lau detailed during a presentation at the American Geophysical Union’s fall meeting, air temperatures in the region have been rising at more than 5 times the rate of global warming. And at high elevations in the eastern Himalayas glaciers have been observed retreating by about 1 percent per decade for the last twenty to thirty years. (In contrast, glaciers in the western Himalayas have been relatively stable).
Though greenhouse gases are responsible for part of the warming, Lau’s research finds that two major processes, both associated with airborne particles called aerosols, also play a critical role. The first, a meteorological hypothesis known as the elevated head pump, involves a shift in the monsoon cycle driven by pollution and dust in the region that Lau’s modeling shows brings warmer and wetter conditions to the Himalayan Plateau. The second involves the deposition of dark particles on snow surfaces so that they decrease the albedo and increase temperatures.