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Mendenhall Glacier, Juneau, Alaska, September 2009
I have visited Alaska four times, and three cruises took us to Juneau, where one fascinating and popular destination is Mendenhall Glacier. An arm of the Juneau Icefield, extending down to Mendenhall Lake.
At one time there was no lake, because the glacier reached to the area which is now a lake.
Mendenhall Glacier, August 2007
It is hard in two years time to decide if you can see the glacier receding. (If I had had plans, when I first visited Juneau, to take comparison pictures on each visit, I would have marked the same spot to take them from.) Actually, over the short course of time a glacier can advance and recede--one step forward and two steps back-like.
Mendenhall Glacier, July 1999
Any difference over ten years is not obvious to the casual visitor. There is a natural cycle of warming and cooling which could explain ten years' dfference. But ten years is not much in the earth's history nor even in human history.
At a ranger program this summer we had an opportunity to view graphs showing climate variations over several centuries. The ups and downs of the graph showed that cycle clearly. Through the middle of the 1800s it looked something like this, with the peaks representing periods of warming and the valleys cooling trends:
Remember what happened over the course of the 1800s? The Industrial Revolution. Coal plants, factories, and all that went with it. What does the graph look like when you add the next 150 or so years to it--the part that comes after mid-1800s? What is the impact of human invention, gas emissions, carbon based fuels? Something like this:
What will Mendenhall Glacier look like if we visit again in ten years?