Nature’s Cooling Albedo Disappearing Faster Than Thought

The loss of sea ice is a concern for more than polar bears, as the loss of reflectivity it represents means the planet may warm even faster.
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The loss of sea ice is a concern for more than polar bears, as the loss of reflectivity it represents means the planet may warm even faster.

Those who reject the notion of climate change often note that there’s a level of prediction in the other side’s concerns, and they correlate prediction with speculation and ultimately conflate it with guessing. That’s not entirely fair, but there is an element of educated guessing going on in developing models that will accurately predict tomorrow’s climate. The assumption from naysayers is that when the models don’t perform flawlessly, that failure can only show that global warming isn’t happening.

But a new study led by the University of Michigan’s Mark G. Flanner and funded in part by the National Science Foundation reminds us that models can fall short in both directions. In this case, looking at data from 1979 to 2008, the best climate models undercounted the “loss of reflectivity” from disappearing snow and sea ice — by about half.

For example, the loss of the North Pole’s ice cap means dark-colored ocean water will absorb solar energy that reflective white ice and snow would otherwise reflect (something known as albedo). The researchers also noted that not all snow and ice is created equal, and variations like ponding water on ice or pollution on snow can influence albedo.

As a release quoted co-author Karen Shell, Oregon State University atmospheric scientist, “Instead of being reflected back into the atmosphere, the energy of the sun is absorbed by the Earth, which amplifies the warming. Scientists have known for some time that there is this amplification effect, but almost all of the climate models we examined underestimated the impact — and they contained a pretty broad range of scenarios.”

In short, less albedo means quicker cooking. And it’s not hard to see a feedback loop in which warmer temperatures mean even less ice, which means even warmer temperatures. As Shell was quoted, “The rate of energy being absorbed by the Earth through cryosphere decline — instead of being reflected back to the atmosphere — is almost 30 percent of the rate of extra energy absorption due to carbon dioxide increase between pre-industrial values and today.”

Keeping tabs on sea ice has been of sufficient import that both NASA and the European Space Agency have sent up satellites specifically to keep tabs on the situation, as our Bruce Dorminey explained last year. When the ESA’s first CryoSat bird crashed near the North Pole in 2005, it hot-footed a replacement that went up last summer.

The albedo researchers were careful not to attribute the loss of ice “entirely” to human activity (or even to something beyond natural variability), but increased ship traffic in the Arctic has raised some concerns. While ships already are blamed for contributing nearly 40 percent as much carbon dioxide to the atmosphere as do automobiles, ships forging a Nortwest or Northeast passage to save fuel also end up dumping smokestack soot on the ice, which accelerates melting.

As Flanner and three co-authors wrote four years ago in another paper, “Reducing Arctic [soot] concentrations sooner rather than later is the most efficient way to mitigate Arctic warming that we know of.”

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