Iceberg B-15A was 76 miles long and 17 miles wide. (Phot0: Josh Landis, NSF)

I know it’s only January but my vote for the year’s Really Cool Sound Award: A  massive iceberg cracks up.

Occasional Climate Watch contributor Tom Banse reports today for Oregon Pubic Broadcasting about a just-released recording of a massive iceberg cracking, creaking, snapping, and groaning as it broke up in 2005 off the coast of Antarctica.  The recording has been condensed, so that you can listen to the five-hour process in just two minutes.

According to Seeyle Martin, the University of Washington scientist who released the recording, the iceberg was 76 miles long and 17 miles wide — about the size of Puget Sound. It shattered when it hit an underwater shoal.  Martin says the sound was recorded by seismic equipment 700 miles away at the South Pole.

Take in the companion radio feature and slide show at The California Report weekly magazine. Gretchen’s slide show also appears below.

Photo: Gretchen Weber

During the two weeks I spent in the Arctic at Toolik Field Station this summer, there was a lot of talk about positive feedbacks and how what happens in the Arctic can affect the entire planet. Thawing permafrost, which I explore in my radio piece for The California Report, is cause for some of the greatest concern.

Another is the loss of sea ice. Mean summer temperatures in the Arctic have risen about three degrees Fahrenheit since 1960, and summer sea ice is shrinking more than 11% per decade.  This year ranks third for the minimum Arctic summer sea ice extent since satellite record-keeping began in 1979.   2007 and 2008 hold the records, and 2009 is in fourth place.

Shrinking sea ice matters not just because it’s an indication of warming, but also because it can accelerate it.  Sea ice keeps polar regions cool by reflecting sunlight and heat, which helps moderate the global climate system. When sea ice isn’t there, the sun hits the surface of the Arctic Ocean instead.   The ocean is relatively dark in color, so instead of reflecting 80% of the sunlight, it absorbs 90%.  This heats up the ocean and the Arctic–which, of course, melts more ice.

Another potential feedback scientists are looking at is “shrubification” (try tossing that one into a conversation), but whether it’s a positive or negative feedback remains up for discussion. As the Arctic warms, the boreal forest is moving north and the tundra itself is changing.  The vegetation is shifting to more woody and leafy plants, like birch, and this change could have varying effects on the climate system. On one hand, more leaves mean more photosynthesis, which could mean that the Arctic vegetation could increase its CO2 uptake, acting as a carbon sink by absorbing CO2 from the atmosphere. On the other hand, increased leafy vegetation would make the landscape darker, which would make it absorb more heat, and that warming could potentially offset any effects of increased CO2 uptake.  Also, the woodier, leafier plants can create protected areas where snow can gather, insulating the ground and keeping it warm.  This too, could have warming effects that offset any additional photosynthesis.

“The takeaway is that it’s complicated, and there’s a potential for large positive feedbacks if things continue in the direction they’re going,” said Donie Bret-Harte, a biologist at the University of Fairbanks and the Associate Field Director at Toolik. “And those large positive feedbacks are things that we won’t be able to control.”

Gretchen Weber in the Valley of the Thermokarsts, ready for the mosquitoes. (Photo: Susan Moran)

Bret-Harte said that some scientists are concerned that the Earth may pass a tipping point, and then it won’t matter how much humans recycle their waste or invest in renewable power or reduce their emissions from burning fossil fuels.  The positive feedback loop will take on a life of its own.

“It’s important to remember that these natural feedbacks that come from melting ice and snow and permafrost are not things we can legislate a solution to,” she said.

“If, they start going, and things get warming, and everything starts to thaw, you can’t say, ‘Well, let’s have a treaty and we’ll stop the thawing,’ because that won’t happen.”

One of the positive feedbacks that scientists are most concerned about in the Arctic, is thawing permafrost, which I explore more in-depth in my radio feature.  With that is a slide show from my reporting trip to “The Valley of the Thermokarsts,” a region on the North Slope of Alaska’s Brooks Range, where researcher Andrew Balser digs into the permafrost for clues about why these areas where chunks of permafrost thaw, form where they do.

A thermokarst study site near Toolik Field Station (Photo: Gretchen Weber)

The Arctic is warming, almost twice as fast as the global average, according to a recent study.  Much of the accelerated warming here is due to positive feedbacks, including one related to the loss of summer sea ice in recent decades.  White surfaces, like snow and ice, reflect most of the sun’s energy and have a high albedo, while the unfrozen ocean absorbs it.  This creates a feedback loop: the warmer the temperatures, the less sea ice.  The less sea ice, the more heat absorbed, the higher the temperatures.  (As Molly Samuel reported recently, scientists are studying albedo as it relates to California’s snowpack and water supply.)

Another concern in a warming Arctic is thawing permafrost.  Earlier this week, I was out with my polar fellow colleagues measuring the depth of the permafrost here around Toolik Lake with a metal probe and a plastic ruler.  In some places we measured it to be just centimeters below a thin surface layer of plant-supporting soil called the “active layer.”

According to Breck Bowden, a scientist from the University of Vermont who studies permafrost here at Toolik, the latest modeling shows that approximately half of the permafrost in the Arctic will thaw in the next 50 years.  That’s significant not just for the Arctic ecosystems, but potentially for the entire planet.  Scientists estimate that there’s one to two times as much carbon frozen in the Arctic soils as there is currently circulating in the atmosphere, said Bowden.   The problem is that as the permafrost thaws, that carbon (mostly in the form of frozen organic matter), some of which has been frozen for thousands of years, will be processed by microbes in the soil and ultimately released into the atmosphere as greenhouse gases: CO2 and methane.

“So why should someone who is living in Alabama, or Nigeria, or the Phillippines worry about what’s going on the Arctic?” said Bowden. “Well, they should worry a lot if there’s going to be a massive amount of CO2 that gets into the atmosphere and your sea level rises or your crops fail because of changes that are related to CO2 changes globally. What happens here in the Arctic is going to affect everything on the globe.”

One indicator that the permafrost in the Arctic is already thawing is the increase in thermokarsts, which are places where the permafrost has thawed and the ground has collapsed, causing a disturbance in the landscape, and often releasing large amounts of sediment into nearby streams. Several scientists, including Bowden, study thermokarsts around Toolik Lake, and they’ve observed that the number of them is increasing.

A group of us were in the field with Bowden yesterday as he paid a visit to one of his research sites about 20 minutes up the Dalton Highway from Toolik Field Station, and a 30-minute hike across the uneven ground that defines the tundra landscape.

Picking our way through the tundra (Photo: Gretchen Weber)

“The Arctic explorers uniformly and universally cursed walking on the tundra, and you can see why,” Bowden explained as we hiked.  “You step on it, you break your ankle. You step between it, you break your ankle.  It’s very lumpy.”

The thermokarst we hiked to was not particularly catastrophic-looking to my untrained eye.  It’s a gully that’s about 300 meters long, 20 meters wide, and about five meters deep.  The collapse happened in 2003, and in the subsequent years it has widened, and vegetation has grown back along its sides, giving them a gentle, convex shape.  Someone like me might have hiked down one side of this thermokarst and up the other without giving it much thought.

Bowden was careful to point out that thermokarsts are a natural phenomenon.  (They also have been known to occur when roads and houses are built in the Arctic without proper insulation.)  But he also believes that the increase in thermokarsts observed in remote areas around Toolik is not natural.

“Thermokarsts have been going on as long as there’s been an arctic landscape, and there have been more of them when it’s warmer and fewer of them when it’s colder,” he said.  “But I do firmly believe that there are more of them now than there were 20 years ago, as a consequence of warming we can document in a variety of places.  The question is, why is the warming occurring?”

Sleeping quarters at Toolik Field Station, at midnight (Photo: Gretchen Weber)

Naively, I thought Alaska’s “Haul Road” would be smooth.  For some reason, I’d pictured the 414-mile route that runs north, from near Fairbanks, to Deadhorse, near Prudhoe Bay, to be a picture of modern asphalt-laying engineering, and that, during our 350-mile drive to Toolik Field Station, I would be able to catch up on some of the sleep I’d been missing after two nights in a University of Fairbanks dorm room (think college students on summer break in a place where the sun barely sets).  After all, this is the road that tracks the Trans-Alaska Pipeline, connecting the largest oil field in North America (which happens to be operated by BP) to the rest of the continent.

As it turns out, I was heartbreakingly wrong.  Roughly a quarter of the road, which is officially called the Dalton Highway, is paved.  And the paved parts are actually the worst. Between the frost heaves caused by the alternate freezing and thawing of the ground, and those Ice Road Trucker tires chewing up the road, driving the Haul Road is more like an amusement park ride, at least from the back seat of a 15-person van.  Suffice it to say that I did not catch up on any sleep during the ride, which turned out to be a good thing, because the second half of this ride was through some of the most beautiful country I have ever seen.

View from just below Atigun Pass (4643 ft) in the Brooks Range (Photo: Gretchen Weber)

About 70 miles north of Coldfoot, one of the three “towns” along the road, and 120 miles north of the Arctic Circle, we passed a sign marking the “Farthest North Spruce Tree.”  It actually wasn’t the farthest north spruce tree we saw, and also, it was dead, but right around there was where we crossed the treeline, leaving behind the white and black spruces stunted from extreme temperatures, and crossed into the tundra.

Back in Fairbanks, over breakfast (reindeer sausage), a biologist named Andi Lloyd had talked about her research on the treeline in Alaska.  There’s a lot of evidence showing that climate in the Arctic is changing faster than any place on Earth.  Here, mean winter temperatures have climbed between six and eight degrees F since 1960, and in summer, between two and three, said Lloyd.  This change is affecting how the boreal forest is expanding, she said, and causing the treeline to move north. In some places, such as the Seward Peninsula, Lloyd says it has moved ten kilometers (six miles) in the last century. “The Arctic is changing faster than we can study it,” said Lloyd.

But the relationship between climate change and the forest is not as simple as warmer temperatures equal northern expansion.  Rising temperatures also mean a drier environment, said Lloyd, as precipitation in the region has not increased as much as temperatures, and more warmth means more evaporation.  Lloyd and others have found that trees in the boreal forest are increasingly drought-stressed, which means they are growing much slower than they did in the mid 1900s, and that they are more vulnerable to insect infestation.

“I had a naive idea that the temperature controlled everything, but then I had a dawning awareness that the boreal forest is a moisture-limited forest,” she said.

There are no trees here at Toolik Station, where I will be for the next two weeks talking to scientists about the changing Arctic. The camp is nestled on the shore of Toolik Lake, in the northern foothills of Alaska’s Brooks Range. During the time I am here, the population of the camp will be about 140 people.  We arrived at 10 p.m., after 13 hours of driving, and the sun was still high in the sky.  It was still up there casting shadows when I awoke at 2:30 a.m.  At breakfast time, however, camp is encased in fog, and the temperature is about 45 degrees–kind of feels like I never left San Francisco.

Climate Watch associate producer Gretchen Weber is spending two weeks at Toolik Station, as a Logan Polar Science Fellow.

Entering the Brooks Range along the Dalton Highway (Photo: Gretchen Weber)

Yosemite's Dana Glacier in 2008, and a photo of it from 1883. Photo: Gretchen Weber

Years of exhaustive (and exhausting) field work out of Portland State University has produced some stunning visual images online.

Not quite two years ago, reporter Sasha Khokha and I joined geologist Hassan Basagic on a long trek to photograph the Dana Glacier, located just inside the eastern edge of Yosemite National Park.  Since 2003, Basagic has been documenting the changes in the glaciers of the Sierra using historic photographs, and we joined him in September of 2008 to see the shrinking glacier for ourselves. We documented the trip with a radio report, an audio slide show, and web videos.

That field work was part of a project called “Glacier Rephotography of the American West” which tracks the retreat of glaciers across the western United States over the last century.

Tom Knudson of the Sacramento Bee, who has closely followed the project, tells us that it has produced a new online resource. It includes a series of interactive time lines that showcase historic photos as well as more recent ones (including Basagic’s) that, when viewed side by side, offer some startling views of how glaciers in various regions have changed.

For more remarkable images of moving glaciers, explore the “Extreme Ice” episode of the PBS series Nova.

The Dana Glacier, outside Yosemite, CA, September 2008. Photo: Gretchen Weber

Yet another climate controversy has revived what have become increasingly common attacks on scientists’ credibility.  The latest flap arose when  the IPCC admitted on Wednesday, that its 2007 prediction that Himalayan glaciers could melt away by 2035 was unfounded.

Attacks on the integrity of scientists have brought about a “loss of innocence” in the climate science field, said Ben Santer, a Research Scientist for Climate Model Diagnosis and Intercomparison at Lawrence Livermore National Laboratory.

On a conference call with reporters Wednesday, Santer lamented that “Fourteen or fifteen years ago, it was possible to do science and not be too worried about being the subject of Congressional investigations, Freedom of Information Act requests, and very personal and very public attacks. Those innocent days are over now.”

Santer, who’s been a key author of some IPCC reports, said the science that goes into those reports is the most rigorous that he’s seen in his career.”If your research suggests that humans are having a pronounced effect on climate,” he continued,  “I think the expectation is that you will be subjected to tremendous scrutiny.  And some of that is appropriate, certainly in terms of the science and the integrity and credibility of the science, but unfortunately, that scrutiny is moving to very unwelcome areas, and it’s also focusing on individuals and motives, and all of this stuff is very distasteful,” he said.

Santer was joined on the call by Lonnie Thompson, a glaciologist at Ohio State University’s Byrd Polar Research Center , who raised concern that the intense and personal nature of much of the criticism climate scientists have been facing (most recently in response to the East Anglia hacked email incident, now widely known as “Climategate”) may be keeping promising young scientists out of the field at a time when they are most needed.  In the wake of the East Anglia emails, a blizzard of accusations of data manipulation blew through the blogosphere and in certain corners of the Senate.

“It does make it difficult to bring young scientists into the field,” Santer agreed.  They look at what has gone on and there is genuine concern there. They must be asking themselves, ‘Do I really want to get involved in critical but possibly contentious issues if there is the possibility that I will spend months or even  longer dealing with questions not about the science that I have done, but about my own personal integrity?’” said Santer.

Thompson affirmed that while it’s difficult to put a specific timetable on the disappearance of glaciers, the scientific evidence documenting glacier recession is overwhelming.  Research indicates that more than 90% of the world’s glaciers are receding, he said, including approximately 95% of the glaciers in the Himalayas.

“Glaciers do not have any political agenda,” said Thompson.  “They just sum up what’s happening in the environment and they retreat or react to that en masse.”

The conference call was organized by the activist Union of Concerned Scientists.

UPDATE 1/25/10
The London tabloid, the Daily Mail, reported yesterday that a lead author of the Asia chapter of the IPCC’s 2007 assessment admitted that he knew the 2035 claim was unsubstantiated, but he approved including it in the report anyway.  Murari Lal reportedly said in an interview with the Daily Mail that he knew the 2035 number came from a report that was not peer-reviewed, but that the claim of imminently disappearing glaciers would, “impact policy-makers and politicians and encourage them to take some concrete action.”

Michael Schlesinger, a professor of Atmospheric Sciences and director of the Climate Research Group at the the University of Illinois at Urbana-Champaign responded to the Daily Mail report with dismay.

“I am greatly saddened and deeply offended by this person’s behavior,” he wrote in an email. “A scientist does not lie nor change the facts to suit an agenda.  Rather s/he tells it as it is, as best as it is known to her/him.”

[Lal] He said these were “the most vilest allegations” and denied that he ever made such assertions.  He said “I didn’t put it [the 2035 claim] in to impress policymakers….  We reported the facts about science as we knew them and as was available in the literature.”

To help sort some of this out, I asked for responses from two highly regarded scientists in the field. Here’s a response to the specific reader challenge from Mark Serreze, Director of the National Snow & Ice Data Center, in Boulder, CO:

It is unclear what Mr. Steele is trying to get at with reference to the seasonal cycles in sea ice extent from the AMSR-E data. The AMSR-E data, while valuable, only go back to 2002. Through combining SSM/I and SMMR satellite data with other information sources for earlier years, we have a decent record of Arctic sea ice extent going back to the early 1950s. The relevant issue is the long-term decline in end-of-summer (September) ice extent evident in this record, with the extreme September minima of recent years (represented in the short AMSR-E record) serving as exclamation points. The observed rate of September ice loss exceeds expectations from nearly all climate models.

I also turned to Waleed Abdalati. Now director of the Earth Sciences Observation Center at the University of Colorado, Abdalati is a veteran of the Cryospheric Sciences and Terrestrial Hydrology programs at NASA, and one of the most articulate people I’ve heard speak on the subject of polar ice. He offers the following:

I am not an expert on polar bears, but I do think it is safe to say that
 their primary habitat, the Arctic sea ice, is severely threatened.  I, and 
most of my colleagues believe we are well on our way to an ice-free Arctic
 in summer any time between this decade and the next 40 years.

This
 is because of two things:  1) it will be decades before the ocean has 
finished its response to present-day greenhouse forcing, so the impacts of 
what we’ve done already have not been fully realized; and 2) the loss of
 sea ice is self-compounding: when it starts to shrink, exposing a 
darker more (heat) absorbing ocean underneath, the likelihood of its continued
 shrinking is greater (ice melts, exposes darker ocean, absorbs more heat, 
melts more ice, exposes darker ocean, and so-on).

Of course the flipside
 of this is that as ice starts to grow, it is more inclined to grow, but
 against the backdrop of the increased warming, the former is far more likely 
than the latter. Finally, as thick multi-year ice disappears, it is
 replaced with thinner and younger ice that is more vulnerable to surface 
melt from the atmosphere, bottom melting from sea water, and being carried
 away to lower, warmer latitudes by ocean current and wind.

So back to the polar bears: If their habitat disappears and they are unable 
to hunt seals, their main source of food, they seem to stand little or no
 chance of survival. I am not a wildlife biologist but its hard for me to 
believe they as a population can sustain themselves on land and with only a
 seasonally-present ice cover. In some cases, the fact that they face more
 challenges on sea ice than in the past, has driven them to forage inland,
 creating the illusion in some people’s minds that their populations are 
increasing, because there are more sightings on land. Who knows? Maybe 
they’ll evolve to hibernate in late summer, when there is no ice, and hunt
 the rest of the year.

There is an added effect that doesn’t get much attention.  There was a 
fascinating study by a Canadian Biologist (Ian Stirling) and a sea ice
 expert (Claire Parkinson) [Stirling, I., and C.L. Parkinson. 2006. Possible 
Effects of Climate Warming on Selected Populations of Polar Bears (Ursus
maritimus) in the Canadian Arctic. Arctic 59(3): 261-275.], which suggested 
that the bears are also losing weight, and approaching the weights at which 
they have historically not been able to bear cubs.  So not only is the
population threatened by starvation, the ability to replenish the population
 seems diminished.

I don’t believe we can say anything with absolute certainty,
 so I, myself would not make the statement that the polar bears are doomed–but I will say that the outlook for them, in my view, looks very, very bad.

Photo: US Fish & Wildlife Service

Because our charter at Climate Watch is to examine climate change from the California perspective, you don’t see a lot here about melting ice caps and imperiled polar bears. But Michael Krasny’s interview with Richard Ellis on KQED’s Forum program is well worth an hour of your time.

Ellis is the author of On Thin Ice: The Changing World of the Polar Bear (Random House, 2009) and it’s fair to say that he managed to stun Krasny with a declaration that the species is “doomed,” no matter what we might try to do to save it at this point. Ellis says there is already too much warming in the pipeline (what scientists call “committed” warming) to reverse the disintegration of the bears’ arctic habitat.

Polar bear populations have been a topic of persistent confusion, recently amplified in an op-ed piece written by former Alaska governor Sarah Palin for The Washington Post.

According to the advocacy group Polar Bears International, there is little room for doubt about the animal’s decline. The organization’s website breaks down the numbers, which point to a “scientifically documented decline in the best-studied population, Western Hudson Bay, and predictions of decline in the second best-studied population, the Southern Beaufort Sea.”

The PBI analysis goes on to explain that:

The Western Hudson Bay population has dropped by 22% since 1987. The Southern Beaufort Sea bears are showing the same signs of stress the Western Hudson Bay bears did before they crashed, including smaller adults and fewer yearling bears.

At the most recent meeting of the IUCN Polar Bear Specialist Group (Copenhagen, 2009), scientists reported that of the 19 sub-populations of polar bears, eight are declining, three are stable, one is increasing, and seven have insufficient data on which to base a decision. (The number of declining populations has increased from five at the group’s 2005 meeting.)

Regardless of whether you share the conclusions of Ellis and PBI about the future of the “poster child for global warming,” the Forum interview is a fascinating hour.

Crater Glacier on Mount St. Helens

We’re entering the best time of year for fans of glaciers.  The high-country rivers of ice are getting their annual nourishment from winter’s snows–probably not enough, as Yosemite National Park geologist Greg Stock tells us: “Glaciers are getting about the same amount of snowfall each winter but they’re seeing a lot more melt in summertime because of those warmer temperatures.”

A database called Glaciers of the American West posits that, “Perhaps glaciers are the clearest expression of climate change.”  But within that National Science Foundation-funded database can be found a few growing glaciers–curious exceptions that buck the general melting trend.  Cherry-picking those exceptions allows some global warming skeptics to suggest we should be preparing for the next ice age (see here and here for examples of this). However, a closer examination of the anomalous glaciers suggests that unique circumstances are more likely at work.

USGS hydrologist Joe Walder

Crater Glacier on Mount St. Helens in southwest Washington State is a dramatic example of a growing glacier.  The glacier formed in the shaded recesses of the high elevation crater left by the catastrophic 1980 eruption of the volcano.  USGS research hydrologist Joe Walder told us the mass of ice and rock is advancing some 300 feet per year.  This time lapse video (file will download) provided by the U.S. Geological Survey shows why glaciers are also known as “rivers of ice.”

Another view from above shows how Crater Glacier got squeezed and pushed around when Mount St. Helens reawakened in 2006 and extruded a new lava dome.  That the young glacier survived the renewed eruption is remarkable by itself.  The fact that the horseshoe-shaped glacier is gaining mass indicates just what a perfect setting Mother Nature created at the volcano.  The north-facing crater acts like a catcher’s mitt reaching toward the moist jet stream.

Mount Rainier, also in Washington State, is the most heavily glaciated peak in the Lower 48 states.  On Rainier’s east flank, Emmons Glacier is advancing. The National Park Service offers this myth-busting explanation:

“The Emmons Glacier experienced a rock avalanche in 1963, which covered part of the glacier with a layer of rock debris. This debris now insulates the ablation (melting) zone of the glacier from sunlight and warm air temperatures and the melting of the glacier is smaller than from an otherwise clean glacier. Because melting is reduced, but the ice flow is the same, the glacier is advancing. This response has nothing to do with climate change.”

Mount Shasta

Something yet again different appears to be happening at northern California’s Mount Shasta. A research team from UC Santa Cruz documented 50 years of nearly continuous expansion of the two largest glaciers on Mount Shasta.  The researchers theorize in the journal Climate Dynamics that Shasta’s glaciers are benefiting from a warming Pacific Ocean. A warmer ocean means more evaporation, and hence more moisture blows over the high peaks near the coast.  Because of Shasta’s height, the enhanced precipitation mostly falls as snow, adding to the mass of the glaciers.

Portland State University glaciologist Andrew Fountain says no one has yet explained to his satisfaction why glaciers on peaks immediately to the north and south of Mount Shasta are not likewise growing.  It is as if a “snow gun” is aimed directly at Shasta’s 14,162-foot summit.  But he doesn’t lose sleep over that issue because Fountain and the other glaciologists who have studied Shasta do not expect the glacial advance to last.  Their climate models call for the snow level (elevation) to rise.

“We do expect it to be a temporary phenomenon,” Fountain said.  “The modeling done down on Mount Shasta expects the glaciers to retreat within the next decade or so, if they’re not already.”

Tom Banse’s radio feature on the West’s growing glaciers airs Monday morning on The California Report.

Chris Field, who is working on the next IPCC report, said “There is a real risk that human-caused climate change will accelerate the release of carbon dioxide from forest and tundra ecosystems, which have been storing a lot of carbon for thousands of years.”

Field, a professor of biology and of environmental Earth system science at Stanford, and a senior fellow at the Woods Institute for the Environment, issued a warning for members of the American Association for the Advancement of Science (AAAS) in Chicago today: “We don’t want to cross a critical threshold where this massive release of carbon starts to run on autopilot.”

And yet, that would appear to be path that we’re on. As Field told the AAAS symposium, “We now have data showing that from 2000 to 2007, greenhouse gas emissions increased far more rapidly than we expected, primarily because developing countries, like China and India, saw a huge upsurge in electric power generation, almost all of it based on coal.”

So what would some of the consequences be? “Tropical forests are essentially inflammable,” Field said. “You couldn’t get a fire to burn there if you tried. But if they dry out just a little bit, the result can be very large and destructive wildfires. It is increasingly clear that as you produce a warmer world, lots of forested areas that had been acting as carbon sinks could be converted to carbon sources. Essentially we could see a forest-carbon feedback that acts like a foot on the accelerator pedal for atmospheric CO2.”

The loss of functioning forests worldwide is already estimated to account for about 20% of carbon emissions. But field also warns of another carbon burst from decomposed plants that have been locked in permafrost for tens of thousands of years. As if all that weren’t plenty, Field says the accelerated forest destruction and melting permafrost could combine to create a “vicious cycle” of accelerated carbon emissions.

Field sums up by saying: “We now know that, without effective action, climate change is going to be larger and more difficult to deal with than we thought.”

The Chicago symposium is being held to address new developments since the last IPCC interim report, in 2007. A formal update is due out next year. Field is co-chair of the IPCC’s Working Group 2, which is assessing the impacts of climate change on social, economic and natural systems.