Inconvenient Truths for Al Gore - Episode 4: Moulins
"When the [melt-]water reaches the bottom of the ice, it lubricates the surface of the bedrock and destabilizes the ice mass, raising fears that the ice mass will slide more quickly toward the ocean.” (AIT, 192)
Seems plausible, but only because Gore rips these images out of their context. The photograph and diagram come from a NASA study published in Science magazine in 2002. The study found that “moulins”—vertical water tunnels formed from pools of melt water at the surface of the ice sheet—accelerate glacial flow in the summertime, but the increase in speed over the entire year is no more than a few percent.
For example, in 1998, moulins contributed such a tiny additional amount of movement that, were it not for satellite measuring systems, nobody would even notice.
Something else Gore doesn’t mention: Greenland was actually warmer in the 1930s and 1940s than it is today.*
What this means is that Greenland in the 1930s and 1940s probably had more ice melt, more “moulins,” and more glacier acceleration than we observe today. Yet there was no major loss of grounded ice.
Gore also warns that half the Greenland Ice Sheet could melt. But according to the Intergovernmental Panel on Climate Change, melting half the ice sheet would require a thousand years of additional sustained warmth, making speculation about such events pure guesswork.
What matters is this: The Greenland Ice Sheet is gaining mass in the interior and losing mass at the edges. When the gains are subtracted from the losses, the net rate of ice loss translates into about 1 to 2 inches of sea level rise over a century—hardly a catastrophe.
Gore calls global warming a “planetary emergency,” but his doomsday scenario is science fiction.
* Los Alamos scientist Peter Chylek in Geophysical Research Letters.