Dozing polar bear, Indianapolis Zoo

Monday, July 30, 2007

Glacial Recession -- Part II

Now that I’ve offered an ominous opener, let me throw out this confusing fact: The glaciers in northwest Montana began to recede in the 1850’s. I know that all of you – astute observers of human history that you are -- will recognize that decade as preceding significant human-generated carbon emissions.

So what gives? This was the question the instructor, Jeff, posed during his introductory slide show. Is the recession of the park’s glaciers caused by humans or is it merely the result of a naturally occurring warming period?

It’s both, of course; the question poses a false dichotomy. Geologic history is peppered with alternating periods of glacial advance and retreat, and the earth had already entered a period of glacial retreat when we started energetically pumping carbon into the atmosphere. So while human activities may not have caused the glaciers to begin melting initially, it’s a safe bet that those activities have dramatically increased the rate, in recent times, at which the glaciers are melting.

Take a look at the picture below.

Where Jeff is standing marks the point to which the glacier extended just last year, and it will recede even further yet this year. And this is on the side of the glacier and not the “toe” – in laymen’s terms, the tip – of the glacier, where melting occurs most rapidly.

It’s also worth noting that this is the kind of thing you hear the wishful thinkers say all the time: “But the glaciers started melting long before the petroleum era, so it can’t be global warming! We’re just in a naturally occurring warming period!” The foundational facts are correct, to be sure -- the glaciers did begin to recede awhile ago, and we are in a natural warming period (or, as I understand it, the end of a much cooler period, which may not be exactly the same thing.) It’s the conclusion they reach that’s faulty. The era of human-generated carbon is coinciding with that period and elevating the planet’s temperature to the point of grim consequences.

Part III: Wherein I attempt to avoid becoming a permanent part of the glacier, as glacial recession, though occurring rapidly, will not happen quickly enough to free me from a crevasse should I be so unlucky as to fall into one.


Kristy said...

Oooo! I'm on pins and needles for Part III!

kris said...

This is very interesting - sounds like a good workshop. The first photo of the lake is beautiful. It's always fun to see where people insert the truth and then jump to reach a conclusion... looking forward to hearing more.

Trailhead said...

Kristy, I'm exaggerating as usual. I was such a weenie about being on that glacier I pretty much stayed rooted to one spot.

Kris, It was a great seminar. I'd encourage anyone to check out the Glacier Institute. They really do a good job and have great classes.