Fire and Ice
The melting point of climate change
Wednesday, December 4, 2013
From long history written in deep rocks, in high glaciers, in dark starry arctic nights, we might know the temperature of the Earth.
Geophysicist Henry Pollack spent years measuring the temperature of rocks drawn from deep bores. He trekked mountain glaciers and the polar reaches of Antarctica. He fetched water from the Great Lakes and Colorado streams. From these samples and many others collected from remote locations and sources, overlaid each one on top of the other, the University of Michigan professor and 2007 Nobel Peace Prize laureate is able to assemble an image of sorts, with the marked increase of global temperatures directly in the crosshairs.
Collection efforts from stone and ice are different, Pollack explains. “One is looking at below the surface of the Earth, the other is looking at the waters and precipitation at the surface.
“Nature’s best thermometer, perhaps its most sensitive and unambiguous indicator of climate change, is ice,” Pollack notes. “When ice gets sufficiently warm, it melts. Ice asks no questions, presents no arguments, reads no newspapers, listens to no debates. It is not burdened by ideology and carries no political baggage as it changes from solid to liquid. It just melts.”
Measuring historic temperatures from a variety of data sources in stone and ice “we are quite able to reconstruct the last 500 years of climate—sometimes as much as 1,000 years ago—which, in the period of overlap with weather station records, it’s a dead overlay,” Pollack explains. “That gives us confidence that what we reconstruct from times before the weather stations has validity as well.
“The consequences of climate change are not something for the future,” Pollack warns. “They’re happening right now.”
Looking at data from a variety of sources, “we see acceleration of severe weather events, an acceleration in the rise of sea level, an acceleration in the loss of mountain glaciers. All of those consequences are moving faster than they have in the past several decades, and even changes in the past several decades have been very noticeable,” he says.
“In the Pacific Northwest, there is less snow falling and more rain falling. The rain falls into the streams straightaway and doesn’t get stored in the snowpack. So we’re seeing shifts in what we call the hydrographs, the timing of stream flow, on an annual basis. Peak flows are coming earlier in the hydrological year. The volumes are being changed in some areas.”
That creates huge consequences, as cycles of water availability become mismatched to cycles of water uses in agriculture, in hydropower, and ecological function. The risk, Pollack notes, is that fresh water simply flows too quickly to the sea without doing important work along the way. Layered on that are the consequences of extreme weather events in a warmer atmosphere.
“Not only are we seeing changes in the timing and the volume of precipitation and stream flow,” Pollack says, “but extreme events—where you get huge amounts of precipitation in a very short time—agriculture again is badly damaged by those events, the economic damage is considerable.”
As ice melts from towering glaciers, it seeks a new level—sea level—that gives rise to the seas. The atmospheric physics are pretty straightforward—warm water has a larger volume than cooler water.
“Currently, thermal expansion is at about the same magnitude in terms of sea level rise as new water entering the oceans,” Pollack agrees. “But if we start to lose Greenland and Antarctica, then the water component will overtake the thermal expansion.
“We have a complete range of sea level change,” Pollack observes. “On the one hand sea level is lower during an ice age because the water that evaporated from the ocean and fell on the continent stayed there as ice. That led to a lowering of sea level. You see that, for instance, in the land bridge that formed between Asia and North America. on the other hand, if we would take all the ice that is currently available on the continents—primarily Antarctica and Greenland—and return that to the oceans, sea level rises. That’s already begun. If we were to lose all of the ice, it would be a very unhappy circumstance. Sea level could be as much as 80 meters higher. Around Puget Sound, that would not be popular.
Just as data can accumulate to provide conviction about climate change, denial can accumulate to slow public policy response to climate change.
“There are several different stages,” Pollack notes, “which I call the Four Trenches of Denial.
“The first is that for a long time you had people saying, ‘Well, climate isn’t changing, you’re just imagining it.’ They’ve backed out of that, the public largely recognizes that is a bogus argument.
“The second trench is, it is happening but it is all related to natural cycles, we’ve had climate change long before there were people—which is true!—but scientists have examined both the natural causes and the new player on the block, the human causes, and measured the strengths of both. Since the mid-20th century, the human factor has overtaken all the natural factors.
“The third trench is, ‘O.K., it’s happening, humans are causing it, but we’re going to love it. Who wouldn’t like it to be warmer?’ But that is a thin argument, too, because the consequences are so severe.
“The last trench is, ‘All right, it’s happening, it’s bad, but we can’t afford to do anything about it.’ That’s where policy comes in. I again think that will be proven a weak argument: We can’t afford not to do something about it.
Perhaps there’s a fifth trench: Oops, too late, no point in even trying now.
“I don’t think so,” Pollack counters. “I am optimistic there’s still time, but we need to get working on policy.
“We’re in the middle of a transition,” Pollack says, “and we really don’t know yet where that transition is going to take us. I’m still moderately optimistic that if we take the problem seriously, but it is not an easy task.”
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