Background
The author notes that "mountain glaciers and ice caps provide the most readily visible evidence of the effects of climate change, and are, therefore, key variables for early-detection strategies in global climate-related observations." Hence, he felt it important to "survey progress in studying the responses of mountain glaciers to climate."

What was done
Barry "outlines the measurements that are available, new techniques that incorporate remotely sensed data, and major findings around the world," focusing on changes in glacier area.

What was learned
Data from most parts of the planet indicate there have been major reductions in ice area since the "beginning of the end" of the Little Ice Age, with apparent accelerating losses over the past couple of decades; and in a postscript to his review, Barry states that "an updated assessment of world glaciers and ice caps indicates ... an accelerating contribution of glacier wastage to sea level rise from 0.51 mm/year for 1951-2003 to 0.93 mm/year for 1994-2003 (Dyurgerov and Meier, 2005)."

What it means
Although Barry's findings are rather doleful, he writes that "a comprehensive survey of global glacier trends is not yet possible [our italics] given the limited observations [our italics] and their incomplete spatial coverage [our italics]." More specifically, he says that "fewer than 300 glaciers worldwide have mass balance measurements and, of these, time-series data are only available from about 50 glaciers."

Summarizing where the science of the subject stands currently, Barry laments that "many problems remain ... notably, the currently insurmountable paucity [our italics] of glacier observations for several key mountain regions of the world and the maldistribution [our italics] of existing mass balance monitoring sites." Hence, it would seem fair to say that the conclusions of Barry's review are not incredibly robust, although he claims that "the major trends are not in doubt," thereby producing something that can simultaneously energize and frustrate people on both sides of the global warming debate, as well as the vast ocean of non-specialists (the public) that vacillates back and forth between them.

Reference
Dyurgerov, M.B. and Meier, M.F. 2005. Glaciers and the Changing Earth System: A 2004 Snapshot. Occasional Paper 58, Institute of Arctic and Alpine Research, University of Colorado.