Double Exposure at the Carnegie Natural History Museum | Program Notes

Double Exposure at the Carnegie Natural History Museum

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Lately, it seems, the deniers of climate change are getting busy again. Like groundhogs predicting spring from a single whiff of February air, some of them take one cool summer as proof that the planet really isn't warming after all.

But of course, as climate scientists have said all along, there's more influencing the earth's surface temperature than the sunlight that greenhouse gasses trap. Solar cycles and phenomenon like El Nino can temporarily keep things cooler than they might otherwise have been, as they've done for the past couple years. That's why warming moves in fits and starts, rather than ratcheting regularly upward, as the deniers would require for proof of a disaster in the making.

(It should be noted that not all climate-deniers refuse to believe the planet's warming; they merely argue, against scientific consensus, that it's not humans who are causing the problem.)

Nonetheless, the majority of this country's warmest years on record have come in the past couple decades. And this singular photography exhibit, in an out-of-the-way corner of the museum's third floor, provides further startling evidence of climate change's uneven and likely catastrophic effects.

The exhibit consists of a matched series of aerial black-and-white photos of glaciers in Southern Alaska. One set was taken in 1938, by noted photographer and cartographer Bradford Washburn. The second was shot in the same locations, at a similar time of year, by former Boston Globe staffer David Arnold, in 2006.

The contrast is striking. Mendenhall Glacier (near Juneau), Valdez Glacier (at the terminus of the Trans-Alaska Pipeline), Shoup Glacier, Knik Glacier -- in each case, dark rock is visible that was once majestically sheathed in ice and snow.

Typically, climate change has meant Alaska actually gets more snow -- but not enough to keep up with accelerated ice melt. Shoup, for example, has retreated 60 miles, half of that in the past two decades.

And the exhibit reminds us that so far, at least, the weather in places like Southwestern Pennsylvania doesn't reflect climate change much. The earth's actually warming faster toward the poles, largely because dark exposed rock and water absorb heat, where once ice and snow reflected it back into space. Blackstone Bay's Alaska winters, for example, are 10 degrees Fahrenheit warmer than they were 70 years ago.

It all bodes ill for the climate we've known since the last ice age, the one in which civilization developed. Fed by ice melt, ocean levels are rising, and could get up to 6 feet higher by 2100, the exhibit says -- bad news for the tens of millions of people living near sea level. Glaciers contain 70 percent of the earth's fresh water, foretelling shortages of water for drinking and irrigation. Hundreds of thousands of species that evolved to survive in particular terrains, or certain temperatures of water, are threatened, endangering the web of life that sustains what we call "nature," which in turn sustains us.

Double Exposure, credited to Arnold and Gabriela Romanouw, is on display through Sept. 13. It includes plugs for renewable energy and warnings about continued subsidies for fossil fuels. It also includes a video interview with the late Washburn, who self-deprecatingly introduces himself by saying, "I'm all that's left of Brad Washburn … And he's disappearing fast!"

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