CHAPTER 3

Opinion evolves with evidence

As nervous as he was about their equipment, Muenchow was much more in his element here than he had been in 2010, testifying before Congress. Then, Muenchow’s scientific caution and compunction for rigor didn’t translate very well for a political audience.

Petermann glacier had just lost a chunk of its ice shelf, and NASA satellite images of the enormous ice “island” were circulating widely. At the hearing, Jay Inslee (D), then a congressman and now the governor of Washington, pressed Muenchow to be more outspoken about what was happening to the planet. The scientist demurred.

The evidence “does not conclusively prove that this specific event is global warming,” Muenchow testified. The logic was simple — breaking off large pieces might just be something Petermann glacier does occasionally, if you go back far enough in time.

But two years later, another vast island of ice cleaved from Petermann. That’s when Muenchow began to change his mind. The shelf had by then lost 23 miles of its prior length, reaching a record low in size.

“It’s two extreme events in six years, so something is happening,” Muenchow said.

In science — unlike in politics — being hesitant when you don’t know something, and being willing to change your mind in the face of new evidence, are virtues. He has since joined a growing wave of researchers working to learn more.

Climate change doubters have continued to suggest — from a distance — that Petermann’s huge ice losses are just normal glacier behavior. Muenchow himself, no dogmatist about the matter, can still entertain the case for skepticism, in part because the glacier has never been as well observed as it now, by scientists and satellites. Conceivably, it lost as much ice during previous periods as it has lost in the present. Muenchow doubts that – the idea that the glacier has shifted to a new state, he says, is supported by the “preponderance of the evidence.”

Petermann is looking suspicious again: At its front edge near the ocean, it features several additional cracks, including one that penetrates further toward the center than the others, arcing inward toward the central river and the shelf’s thinnest region.

“I already see the beginning of a third break-up,” Muenchow said.