Arctic Sea Ice: A Single Season Does Not a Significant Trend Make

On June 27, The Independent in London ran a story that read “Exclusive: No Ice at the North Pole.”

The headline was off on two counts: there was nothing exclusive about the story, and it’s premature to say the North Pole is ice-free.

Andrew C. Revkin, in his DotEarth blog for The New York Times, reported as much when he posted a piece later in the day about what’s going on with Arctic sea ice, who’s tracking the changes and how the media are covering it.

The climate change blog, RealClimate, also weighed in on the news story, pointing to some of the dynamics involved in the emergence of open water at the North Pole.

First, an acknowledgement: there is a documented decline of thick years-old sea ice in the Arctic, and an increase of much thinner, seasonal sea ice that is much more vulnerable to summer melting.

However, when it comes to forecasting whether the North Pole is going to be ice-free in any given year, Revkin captured the view of many scientists: “It’s pretty much impossible to make such a prediction with high confidence.”

It wouldn’t be the first time that a hyped headline overstated the science. And when it comes to covering changes under way in the Arctic, reporters should resist the temptation to do that in their news stories.

Without a doubt, climate change is profoundly and rapidly altering the Arctic environment – amplifying the summer retreat of sea ice, thawing permafrost, making lakes and peat bogs more vulnerable to methane venting, and accelerating melting glaciers on Greenland.

But variability from year to year can cloud the big picture. Reporters do their readers a disservice when they point to any single development in the Arctic as emblematic of the long-term rise in average global temperatures.

Alley: ‘Nature has a longer attention span’

“Neither a cold year, nor a warm one, a new record low sea-ice level nor a failure to reach one, an open North Pole or an icy one, really changes the picture in a year,” said Richard Alley, a prominent glaciologist at Penn State University and a lead author for the 4th chapter of the IPCC’s Fourth Assessment: “Observations: Changes in Snow, Ice and Frozen Ground.”

The dramatic retreat of summer sea ice in 2007, by itself, “doesn’t matter hugely,” Alley replied by email in response to questions from The Yale Forum. “That it is part of a highly significant and well-attributed climatically significant trend does matter. It appears that some members of the public want to see the next year to decide what is going on; nature has a longer attention span.”

The North Pole may actually become ice-free for a few weeks this summer, but reporters should keep the long view in mind, and place the summer of 2008 in context.

It’s worth noting here that volcanic eruptions on the sea floor beneath the Arctic have “almost no chance of a significant influence” on the melting of sea ice, as Revkin reported on DotEarth recently.

When it comes to understanding climate changes in the Arctic, one of the most significant developments in recent years is the rise in scientists’ confidence that long-term changes in sea ice are being driven by rising temperatures and that at least a lot of that warming is the result of activities by us humans, Alley said.

Robert Corell, program director for The H. John Heinz, III Center for Science, Economics, and the Environment, said scientists’ increased confidence that the Greenland ice sheet overall is melting is also a significant development that reporters should cover. That confidence has come largely from GRACE satellite measurements.

“We now know for certain that it is losing mass,” Corell said in a telephone interview. “The amount of snow coming down is substantially less than what’s melting along the margins.”

One immediate consequence of disappearing sea ice is easy for anyone to understand. Its loss is changing the albedo, or reflectivity, of the Arctic. More deep blue open ocean will absorb more heat than white expanses of ice and snow. And that will accelerate the melting of sea ice that remains – a classic feedback loop.

A paper published in June 2008 in Geophysical Research Letters, “What drove the dramatic retreat of arctic sea ice during summer 2007?” points to changes in the Arctic’s albedo as one of the key drivers of last year’s retreat of summer sea ice.

“Thin ice and open water allow more surface solar heating because of a much reduced surface albedo, leading to amplified ice melting,” the paper’s abstract states. “The Arctic Ocean lost additional 10 percent of its total ice mass in which 70 percent is due directly to the amplified melting.”

Another paper, also published in early June in Geophysical Research Letters, found that ocean warming accelerated melting on the underside of sea ice in the Beaufort Sea during the summer of 2007.

“Solar heating of the upper ocean was the primary source of heat for this observed enhanced Beaufort Sea bottom melting,” the authors wrote in an abstract of the paper. The increase in ice-free, open ocean in the Arctic resulted in a 500-percent increase in solar input into the upper ocean – “triggering an ice-albedo feedback and contributing to the accelerating ice retreat,” the study’s authors said.

Reporting on the details can be just as dramatic, and it can provide a deeper understanding of what’s happening in the Arctic than merely pointing to the possibility of open water at the North Pole.

The biggest challenge for reporters is to maintain the interest of their audiences, engage listeners and viewers while remaining true to the science “and not (getting) caught by ‘weather’,” Alley said. “The discovery and rediscovery that the world has ‘weather’ does not change what the climate is doing!”

One of the major consequences of melting sea ice in the Arctic is the opening of sea lanes and the rush for oil and gas exploration, Corell said. That development will help make the sea ice story immediate and urgent. Geopolitical concerns over who has the right to control the passage of ships, along with issues of who has rights to lease the sea bottom for oil and gas development, will be an important and rapidly developing story.

Corell, who was chair of the Arctic Climate Impact Assessment, released in late 2004, said a follow-up study this fall will examine the implications of opening up the Arctic to shipping.

One final point: While Arctic ice has been declining, Antarctic sea ice has been increasing recently. But changes at the bottom of the world are well within the range of natural variability, Alley said. In contrast, the Arctic changes under way are far outside of it.


Online Resources


A Few Expert Sources

Robert Corell, Program Director, The H. John Heinz, III Center for Science, Economics, and the Environment, Washington, D.C.

Tel: 202-552-4713

Email: Corell@heinzctr.org

Larry Hinzman, Director, International Arctic Research Center, University of Alaska Fairbanks

Tel: 907-474-7331

Email: lhinzman@iarc.uaf.edu

John Walsh, President’s Professor of Climate Change & Chief Scientist
International Arctic Research Center, University of Alaska at Fairbanks

Tel: 907-474-2677

Email: jwalsh@iarc.uaf.edu

Jerry Brown, President, International Permafrost Association, Woods Hole, MA

Tel: 508-457-4982

Email: jerrybrown@igc.org

Richard Alley, Evan Pugh Professor of Geosciences, Penn State University
Phone: 814-863-1700

Email: ralley@essc.psu.edu

Bruce Lieberman

Bruce Lieberman is a freelance writer covering science and environmental topics. He has more than 20 years experience in the news business. (E-mail: bruce@yaleclimateconnections.org, Twitter: @brucelieberman1)
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