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Scientists see ice in Arctic’s near-future
Prefer your Alaska unbaked? Despite longterm warming trends, two Alaska scientists tell Arctic Science Journeys producer Doug Schneider that they believe recent recent rapid change is mostly due to natural short-term cycles, which are due to reverse.
Over the past three decades, the Arctic has become steadily warmer. By some accounts, the Arctic has warmed an average of three degrees—enough heat to melt an area of sea ice larger than the state of Texas.
Some scientists call this the strongest evidence yet that humans are heating up the climate. But others say the short-term warming is part of a natural cycle that has played out across the Arctic for thousands of years, explains John Walsh, a climate scientist and the director of the Center for Global Change and Arctic System Research at the University of Alaska Fairbanks.
“For example, in this most recent century, the Arctic warmed rapidly from about 1900 to 1940, then it cooled from about 1940 to 1970, and then it warmed from 1970 to 2000 at a pretty good rate,” said Walsh. “Now, we don’t know if ... a downtick will set in fairly soon. It could go either way.”
Many scientists say the current warming trend is largely due to global use of coal, gas, and oil. The burning of these fossil fuels releases carbon dioxide and other gases into the atmosphere that slow the escape of heat from the earth, dramatically altering the planet’s climate and weather. Nowhere has the impact been felt more dramatically than in the Arctic.
According to the Arctic Climate Impact Assessment, an international study of the Arctic’s climate that Walsh helped to author, a warmer climate has resulted in the reduction of sea ice, the melting of glaciers, the expansion of trees and shrubs into the tundra, and the thawing of frozen ground called permafrost.
Humans aren’t the only cause of Arctic climate change, however.
Oceanographer Mark Johnson, of the UAF School of Fisheries and Ocean Sciences, has studied the Arctic for more than 20 years. He’s among a cadre of leading scientists who point to natural cycles as the major reason for recent Arctic warming.
“Not all my colleagues would share that, but people who are really in the know say that the variability we are seeing now and in the last 20-30 years is 70 percent natural variability.”
Some of the natural events that can contribute to warming include volcanic eruptions. Dust and soot from volcanoes block incoming solar radiation and can have a cooling effect on climate. But even more important are the natural climate cycles driven by interactions between the ocean and the atmosphere. Such cycles can last decades.
Johnson believes the warming of the Arctic over the past 30 years has been largely the work of such natural ocean-atmosphere cycles. What’s more, he predicts the Arctic climate will become somewhat cooler over the next decade. It’s a trend he says will lead to more sea ice in the Arctic Ocean than has been seen in recent years.
“I personally think we are part of a cycle here,” said Johnson. “While there is a long-term trend of sea ice decline, I think there is going to be more ice. By 2010, I think we are going to be back into colder conditions.”
Looking 50 to 100 years into the future, however, Mark Johnson and John Walsh both agree that the Arctic climate will become steadily warmer overall. But along the way, they say, there will be short-term cold spells. Walsh likens the Arctic’s climate fluctuation to the ups and downs of the stock market.
“One of the best analogies I’ve heard is with the stock market. If you are in a bull market in stocks, and the trend is upward, but in any week or month it could be either up or down. So you have a lot of those shorter term ups and downs are superimposed on a longer-term trend.”
-- Adapted from an Arctic Science Journeys radio item by Doug Schneider.
Arctic Science Journeys is a radio service highlighting science, culture, and the environment of the circumpolar north. Produced by the Alaska Sea Grant College Program and the University of Alaska Fairbanks.
Photo by TERRY WHITLEDGE for ASJ Radio | Posted 02.07.05 at 11:18 pm