The World in 2050_ Four Forces Shaping Civilization's Northern Future - Laurence C. Smith [69]
Compared to land glaciers, sea ice is thin and flimsy, an ephemeral floating membrane just 1-2 meters thick. The greenhouse effect, by melting it back somewhat, thus unleashes a self-reinforcing effect even greater than the greenhouse warming itself. It’s rather as if when struck by blazing hot sun, one discards a white shirt and puts on a black one. By responding in this way to small global temperature changes, sea ice thus amplifies them even more.292
While its global effect is small, the ice-albedo feedback is uniquely powerful in the Arctic because it is the only place on Earth where a major ocean gets coated with ephemeral floating sea ice during the summer. Antarctica, in contrast, is a continent of land, thickly buried beneath permanent, kilometers-thick glaciers. For this and several other reasons, climate warming is more amplified in the Arctic than the Antarctic. 293,294
As an ice-free Arctic Ocean warms up, it acts like a giant hot-water bottle, warming the chilly Arctic air as the Sun crawls off the horizon each winter. The sea ice that does eventually form is thin and crackly, allowing more of the ocean’s heat to seep out even during the depths of winter. Winters become milder, the autumn freeze-up happens later, and the spring thaw arrives earlier. The warming effect is highest over the ocean and from there spills southward, warming vast landscapes across some of the coldest terrain on Earth.
Dr. Smith Goes to Washington
I first met National Center for Atmospheric Research (NCAR) climate modeler David Lawrence in Washington, D.C. We had been brought to the Russell Senate Office Building to brief U.S. Senate staffers on the ramifications of thawing Arctic permafrost. It was exciting. The Russell is the Senate’s oldest building and the site of many historic events, including the Watergate hearings. Its hallways are white marble and mahogany, with important-looking people clacking around in dark power-suits. Just a few yards from our briefing room were the offices of Senator John Kerry and former senator John F. Kennedy. Moments before we got started, the moderator pulled us aside to whisper that Senator John McCain might show up. He didn’t, but it was cool just wondering if he would.
After the briefings and a pleasant lunch reception were over, Dave and I headed out to a local pub for a beer before catching our flights home. Over microbrews, he described his next big idea: figuring out how much northern landscapes might warm up, based purely on the ice-albedo feedback from reduced summer sea-ice. I told him he was on to something. It was critical to separate out the ice-dependent feedback from overall greenhouse gas forcing, I pointed out. That way, if the ice shrank faster than expected, we’d know what the immediate climate response could be—even ahead of the longer-term cumulative effect of greenhouse gas loading. We drained our pints and left. I promptly forgot all about the conversation until eighteen months later when I ran into Dave at a conference. Whipping out his laptop, he showed me a preliminary model simulation of his big idea.295
My eyes widened. I was gazing at a world with northern high latitudes plastered everywhere in vivid orange—a pool of spreading warmth as much as five, six, or seven degrees Celsius (8° to 12°F) higher—spreading southward from the Arctic Ocean. All of Alaska and Canada and Greenland were bathed in it. It grazed other northern U.S. states from Minnesota to Maine. Russia’s vast bulk was lit up from one end to the other. Only Scandinavia and Western Europe, already warmed by the Gulf Stream, were untouched. Then I looked closer and saw what time of year it was.
November . . . December . . . January . . . February. The warming effect was greatest not in summer but during the coldest months of the year. I was staring at a map of the relaxing grip of winter