Glaciers in the Himalayas are shrinking slowly, but their retreat still presents major risks for more than a billion people who rely on glacier-fed rivers, says a new report by the U.S. Agency for International Development.
The agency says more information about the glaciers' behavior is needed to help communities adapt to climate change-driven changes in glacier melt and the region's water cycle. More than 50,000 glaciers help supply water for Asia's major rivers, including the Ganges, Indus, Mekong, Yangtze and Yellow.
"USAID and other development agencies do have some time to address the impacts of glacial melt, but it is important to start looking now at how to make communities more resilient," said Kristina Yarrow, a health adviser to the agency's Asia and Middle East bureaus.
Himalayan glaciers made headlines last fall when news broke of mistakes in the 2007 report of the Intergovernmental Panel on Climate Change. Foremost among them was an error-riddled paragraph that said Himalayan glaciers could disappear by 2035. Scientists who identified the mistakes say the IPCC report relied on news accounts that appear to misquote a scientific paper that estimated the glaciers could disappear by 2350, not 2035. The controversy prompted the IPCC to revise its procedures.
"Peer-reviewed science does not support any of the dramatic statements that have been made about melting or retreat of Himalayan glaciers," said Elizabeth Malone, the new report's lead author and a senior research scientist at the Pacific Northwest National Laboratory. "That reinforces the IPCC's decision to retract a silly statement that made its way into their report. That's pretty clear. Beyond that, we have a lack of knowledge in many areas."
Data remain too sparse
Scientists have data about specific glaciers and are able to discern some trends, but the information is too sparse to paint a clear picture of how fast glaciers are melting throughout the region and how that compares to how they behaved in the past, Malone added.
Part of the problem is that the region's most studied glaciers are largely its most accessible glaciers, often those at lower altitudes. But as the report notes, glaciers at the highest elevations -- between 4,000 and 7,000 meters above sea level (between 13,123 and 22,965 feet) -- are behaving differently than those at lower elevations.
"Higher elevation glaciers currently remain below freezing during much of the year, even in the presence of a warmer climate," the report says.
Scientists are beginning to use satellites to monitor glaciers, giving them access to ice hard to reach by other means. But without accurate historical data, it's still hard to identify broad trends in glacier behavior.
Thawing presents a serious risk
What is clear is that glacial thaw does present serious risks for residents of the region.
As glaciers melt, their runoff often builds up to form lakes that can burst suddenly and inundate nearby areas -- a phenomenon known as a "glof," or "glacial lake outburst flood."
Moreover, glacial melt could affect water supplies for communities that depend on glacier-fed rivers. "Even small changes in glacier melt will result in large impacts downstream from High Asia," the USAID report cautions.
The report calls for a concerted scientific effort to improve monitoring of Himalayan glaciers. It also recommends that aid and development efforts in the region begin working now to improve water efficiency and water conservation, prepare for glofs and the eventual disappearance of some glaciers, and reduce waterborne diseases, malnutrition and conflicts that may arise from future reductions to water supply.
And it lays out a third program to reduce air pollution -- including sooty black carbon -- that harms human health and speeds glacial melt by reducing the ice's ability to reflect, rather than absorb, heat from the sun.
Correction: An earlier version of this story incorrectly named a health adviser to USAID's Asia and Middle East bureaus. The adviser is Kristina Yarrow.