Glaciers are not melting as fast as was thought

Excerpts from an article in The Guardian:

The world's greatest snow-capped peaks, which run in a chain from the Himalayas to Tian Shan on the border of China and Kyrgyzstan, have lost no ice over the last decade, new research shows. The discovery has stunned scientists, who had believed that around 50bn tonnes of meltwater were being shed each year and not being replaced by new snowfall...

The scientists are careful to point out that lower-altitude glaciers in the Asian mountain ranges – sometimes dubbed the "third pole" – are definitely melting. Satellite images and reports confirm this. But over the study period from 2003-10 enough ice was added to the peaks to compensate. The impact on predictions for future sea level rise is yet to be fully studied but Bamber said: "The projections for sea level rise by 2100 will not change by much, say 5cm or so, so we are talking about a very small modification." Existing estimates range from 30cm to 1m.

This is going to lead to lots of misunderstandings, because there are a variety of nuances and caveats in the interpretation of the data.  Posted here so those interested in climate change controversy can start reading up on the new findings.  What amazes me is the methodology -

The new study used a pair of satellites, called Grace, which measure tiny changes in the Earth's gravitational pull. When ice is lost, the gravitational pull weakens and is detected by the orbiting spacecraft...

It's hard for me to comprehend how the effects of gravity created by mountains can be altered by superimposed snow accumulation, or how such differences can be measured.  I'm not doubting, mind you - just having trouble comprehending.

Addendum:  A hat tip to whoever posted in the Comments the link to this video, which discusses this phenomenon (and these results) in detail.