Arctic warming

1. Massive melting

2. Warm, warmer, warmest

3. Plants, animals, people

4. Is help on the way?

A native woman in Alaska, photographed in 1907. Photo: "Obleka." Frank H. Nowell, Nome. Library of Congress

The Arctic is a big lever in climate. Arctic changes could change the world.

Warming causes melting. Exposed water or soil absorbs more solar energy, causing more warming -- and more melting.

Average annual burning of North America's northern forests, in million hectares. Graphics:Arctic Climate Impact Assessment

Global warning: Fearsome feedback in the north?
woman poses in elaborate fur-trimmed coatOver the past 50 years, according to the new Arctic climate assessment, temperatures have risen 1° to 3° C in Siberia, and 2° to 3° in Alaska. The warm-up satisfies early predictions that greenhouse warming would rise fastest near the North Pole.

One reason for the polar emphasis is feedback. Feedback, you'll remember, happens when an effect bounces back to change its cause. Hold a guitar before its loudspeaker, and the sound will feed back louder and louder, quickly shrilling into an ear-piercing screech.

Unless you are Jimi Hendrix. Then feedback will sound like music...

In the Arctic, feedback could hasten the warming caused by greenhouse gases like carbon dioxide and methane, which reflect heat back to Earth.

The feedback mechanism? Melting.

In the Arctic's oven-like future (the ACIA projected that by 2090, all ice in the Arctic Ocean might melt in summer), two feedback loops could occur: Melting snow would increase the land exposed to solar radiation. Ditto for melting ice and ocean. Warming would cause more melting. More exposed water or soil would absorb more solar energy, causing more warming, and causing more melting.

Four maps show observed and predicted Arctic temp increases.
Map shows Western Siberia, Alaska and western Canadian Arctic. Average air temperatures have risen 2-3ƒC in much of this area, except for Siberia. Warming is faster in winter. Computer models predict average annual warming of 3-4ƒC over land and the Bering Sea by the 2090s. Air over the Arctic Ocean may warm by 10°. Graph courtesy Arctic Climate Impact Assessment

Feedback: Forests on fire
Global warming could also spark a second type of feedback: The hotter, drier forests of the north are already burning at unprecedented rates. The ACIA says burning more than doubled in Siberia's vast forests between the 1980s and 1990s. Fires in the west have doubled in North America in 30 years, and could rise another 80 percent after moderate warming.

Two maps of Greenland coast being taken over by the sea. Summer melting on the edges of Greenland's ice cap has increased radically in a decade. Melting glaciers contribute to sea-level rise. They also reduce surface reflectivity, speeding up warming. Graphics:Arctic Climate Impact Assessment

Burning Arctic forests could release up to 1 billion metric tons of carbon into the atmosphere each year, according to the ACIA. That is 15 percent of the record 6.8 billion tons of carbon that came from fossil fuels in 2003.

However, the warming impact of forest fires is unclear, according to Glenn Juday of the University of Alaska at Fairbanks, author of the ACIA chapter on forests, land management and agriculture. By email, he told us, "Certain fires kill overstory trees but do not consume much of the stored carbon on the forest floor, and stimulate vigorous new tree growth. Following such fires there may be a net uptake of carbon [and a reduction in airborne carbon]. Hotter and more destructive fires put more of the forest-floor carbon into the atmosphere at the time of burning, and cause a lag in new plant growth. Those fires contribute to a net increase in atmospheric carbon."

Graph shows recent leap in acres of burned boreal forest.This matters, because the north stores a huge amount of carbon in soils, bogs and tundra. Warming could oxidize some of this vast storehouse into carbon dioxide, perhaps starting another type of dangerous feedback, says Jon Foley. "We don't know how much warming will be needed to liberate soil carbon, but all the climate-change scenarios that have been concluded so far have basically ignored the fact that those things could release carbon."

In other words, he says, climate projections have assumed that carbon stored underground in the north "stays locked up forever." To climate researcher Jon Foley, the main question is not whether, but when, bogs and permafrost will start dumping carbon dioxide into the atmosphere. "We don't know how much could get unlocked, but I would argue it would be more than zero, so our assumptions about future climate change are too optimistic."

In 24 years, the polar ice cap shrank considerably. Less ice translates into more solar energy absorbed, and more global warming. Courtesy Arctic Climate Impact Assessment.
Comparative maps of polar ice cap shrinking in past 20 years.

One giant crowbar
Let's be hard-headed for a moment. The Arctic is a vast place, but lightly populated: Only about 4-million people live there (and only about 10 percent of them are indigenous people with Arctic cultural roots). If warm comes to hot, why not just find them someplace else to live?

chart shows sea level rising in futureDifferent warming assumptions produce different rises of sea level. Courtesy Arctic Climate Impact Assessment

Sure, it might sound a trifle unfair: "Sorry, we polluted your land while we built up our rich industrial economies, but you are welcome to live near us, as displaced refugees. We can't guarantee your culture would survive, but we do offer great canned soup."

Beyond morality, there are also selfish reasons to worry about Arctic warming, says Foley. For one thing, the rapid, unmistakable Arctic warming reinforces the conventional understanding of how greenhouse gases cause global warming. "Physics works, it's no big surprise," Foley says. "When you make a frozen white place warmer, it's going to melt, and it will get darker, and that will aid in warming up in springtime."

The Arctic, Foley maintains, acts like "a big lever in the climate. As it changes, it has implications for the rest of us."

How is warming affecting Arctic people and animals?

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