There is mounting evidence that climate change is triggering a shrinking and thinning of many glaciers world-wide which may eventually put at risk water supplies for hundreds of millions -- if not billions -- of people. Data gaps exist in some vulnerable parts of the globe undermining the ability to provide precise early warning for countries and populations at risk. If the trend continues and governments fail to agree on deep and decisive emission reductions at the crucial UN climate convention meeting in Copenhagen in 2009, it is possible that glaciers may completely disappear from many mountain ranges in the 21st century.