Well, no they're not. Some are, some aren't and some are getting bigger. They vast majority of glaciers we have no idea what they're doing.
"A few years ago, R.J. Braithwaite's peer-reviewed article in Progress in Physical Geography described a "mass balance analysis" he conducted of 246 glaciers sampled all around the world between 1946 and 1995. That's 50 years of data. Braithwaite found some glaciers were melting, while a nearly equal number were growing in size, and still others remained stable.
He concluded, "There is no obvious common or global trend of increasing glacier melt in recent years."
But if your goal is to frighten the public into thinking humans are causing global warming with potentially catastrophic consequences, there is no shortage of melting glaciers to report on. By some estimates, 160,000 glaciers exist on Earth. Only 63,000 have been inventoried, and only a few hundred have been studied in the detail described by Braithwaite."
http://www.heartland.org/Article.cfm?artId=17351