May 23, 2010

Greenland - melting away before our very eyes

A mere shade of its former self. Not so fast from Willis Eschenbach writing at Watts Up With That:
On Being the Wrong Size
This topic is a particular peeve of mine, so I hope I will be forgiven if I wax wroth.

There is a most marvelous piece of technology called the GRACE satellites, which stands for the Gravity Recovery and Climate Experiment. It is composed of two satellites flying in formation. Measuring the distance between the two satellites to the nearest micron (a hundredth of the width of a hair) allows us to calculate the weight of things on the earth very accurately.

One of the things that the GRACE satellites have allowed us to calculate is the ice loss from the Greenland Ice Cap. There is a new article about the Greenland results called Weighing Greenland.

So, what�s not to like about the article?

Well, the article opens by saying:
Scott Luthcke weighs Greenland � every 10 days. And the island has been losing weight, an average of 183 gigatons (or 200 cubic kilometers) � in ice � annually during the past six years. That�s one third the volume of water in Lake Erie every year. Greenland�s shrinking ice sheet offers some of the most powerful evidence of global warming.
Now, that sounds pretty scary, it�s losing a third of the volume of Lake Erie every year. Can�t have that.

But what does that volume, a third of Lake Erie, really mean? We could also say that it�s 80 million Olympic swimming pools, or 400 times the volume of Sydney Harbor, or about the same volume as the known world oil reserves. Or we could say the ice loss is 550 times the weight of all humans on the Earth, or the weight of 31,000 Great Pyramids � but we�re getting no closer to understanding what that ice loss means.
Willis goes on to check a couple of sources for the size of the Greenland Ice Sheet and comes to this conclusion:
So now we have something to which we can compare our one-third of Lake Erie or 400 Sidney Harbors or 550 times the weight of the global population. And when we do so, we find that the annual loss is around 200 km^3 lost annually out of some 3,000,000 km^3 total. This means that Greenland is losing about 0.007% of its total mass every year � seven thousandths of one percent lost annually, be still, my beating heart �

And if that terrifying rate of loss continues unabated, of course, it will all be gone in a mere 15,000 years.

That�s my pet peeve, that numbers are being presented in the most frightening way possible. The loss of 200 km^3 of ice per year is not �some of the most powerful evidence of global warming�, that�s hyperbole. It is a trivial change in a huge block of ice.
And of course, the 0.007% fact is nowhere in the Grist article. Talk about cherry-picking your data... Posted by DaveH at May 23, 2010 10:09 PM
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