If the ice is melting faster than new ice can accumulate,
0:44the glacier shrieks, and is said to be in retreat.
0:49Take a look at these two dramatic photos.
0:51They were taken of the Muir Glacier in Alaska.
0:55The bottom photograph was taken in 1941, where the ice
1:00in the foreground was over 17 metres thick.
1:04The second photograph was taken from the
1:06same position in 2004.
1:09The difference is rather obvious.
1:12While there are a handful of glaciers around the world
1:16whose volume is increasing, the vast majority are
1:20retreating, and retreating quite rapidly.
1:23In fact, the rate of glacial retreat has accelerated a
1:26great deal even since the 1990s.
1:31And take a look at this rather sad image.
1:34It's all that's left of what was once the world's highest
1:38ski resort.
1:39At 5,300 metres on top of the Chacaltaya Glacier in Bolivia.
1:45In the 1990s, scientists started measuring how quickly
1:49this glacier was disappearing.
1:52And they predicted that it was disappearing so quickly that
1:55it would be all gone by 2015.
1:59They were wrong.
2:01It actually completely disappeared by 2009.
2:0618,000 years of ice built-up gone completely.
2:11Well, why is glacial retreat so important?
2:14Well, the reason it's important is that glaciers are
2:17like frozen dams, and as they melt in spring time, they
2:22provide water downstream for agriculture and for many urban
2:26areas, as well as many plants and animals.