New satellite study sparks fresh debate about the melting of Himalayan glaciers.
Satellites can be powerful tools to map complex changes across large, inaccessible areas — but only if researchers are able to interpret correctly what their measurements mean.
A 2010 study using measurements taken by the Gravity Recovery and Climate Experiment (GRACE) satellite reported that glaciers in the Himalayas and the Tibetan plateau were shedding roughly 50 gigatonnes of ice a year. But these results were refuted two years later by another group that used the same data set but interpreted it to show that ice loss was only one tenth of that amount.
Now a third study of Himalayan glaciers, using a different satellite called ICESat, indicates that these glaciers lost an average of 12 gigatonnes ice a year between 2003 and 2008. The work is published today in Nature.
The new estimate raises further questions about satellite and field measurements of alpine glaciers, and ”will set the cat among the pigeons,” says Graham Cogley, a remote-sensing expert at Trent University in Peterborough, Ontario, in an accompanying News and Views article. Although the ICESat results show twice as much ice loss as the re-interpreted GRACE data, this figure is still three times lower than regional losses estimated on the basis of field studies.