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Massive Iceberg Snaps Off Greenland--But What Does It Mean?

Yesterday, a massive ice island four times the size of Manhattan snapped off of Greenland's Petermann Glacier. Ominous, no? A disturbing sign of a warming planet? Well… actually, it's hard to say. It's true that, in a broad sense, Greenland has been losing ice faster than it has been accumulating snow in recent years. The thing's clearly melting. But linking this one specific glacier calving to global warming is more difficult, and something many glaciologists are reluctant to do. Here's Andrew Restuccia reporting from a House hearing this morning:

The House Select Committee on Energy Independence and Global Warming hearing, chaired by Rep. Edward Markey (D-Mass.) unfolded like most hearings on the science behind global warming do. One scientist — in this case Dr. Andreas Muenchow, physical ocean science and engineering professor at the University of Delaware — warns that you can’t point to any one event (i.e., the Greenland glacier fracture) to bolster your arguments about global warming. Lawmakers — in this case Markey — and other witnesses then say that event is part of a broader pattern that shows the planet is warming.

Markey spent much of the hearing engaging in an occasionally tense back-and-forth with Muenchow, who refused to make broad statements about what the Greenland glacier incident says about global warming.

More broadly though, this hearing shows how difficult it can be to use scientific data to sell a political point of view. Politicians are used to smoothing over nuance in order to push key policy priorities. Scientists, by their very nature, are bound by the data they collect. While the data certainly shows that the climate is changing, it can often be difficult to communicate that information effectively.

That last point is crucial. Climatologists tend to be extremely cautious in these matters—which is why right-wing accusations that they're engaged in fraud or alarmism are so absurd. What climatologists can say with confidence is that Greenland is melting, that it will continue to melt as the planet warms (i.e., the sheets will lose ice faster than they accumulate snow), and that this will contribute to sea-level rise. About 125,000 years ago, when the Earth was 3°C to 5°C (due to changes in the Earth's orbit), melted Greenland ice sheets pushed the oceans up as much as four meters higher than they are today. That much is clear. But pointing to a big, headline-grabbing glacier break-off and screaming, "It's global warming! PANIC!"—that's just not something scientists are ever going to do.

But the problem—which Markey and others grasp—is that it's difficult to get people to pay attention to an environmental issue unless there's some big, dramatic event you can point to. (And even then there's no guarantee—note this recent poll finding that many Americans still wouldn't believe in global warming even if Nebraska suddenly turned into a desert.) One of the reasons that the world got together to do something about CFCs is that there was a big, easily depictable ozone "hole" swarming around the Antarctic. You could make a picture of it and slap it on Time magazine. Whereas slow, gradual changes—even if they all add up to catastrophe—don't seem to fill many people with the same sense of urgency. Which is why climate is such a difficult issue to tackle.

(Flickr photo credit: NASA Goddard)