INDEPTH: CLIMATE CHANGE
The evidence: making the case for climate change
CBC News Online | March 24, 2005
The snow-covered terrain of the Arctic appears to be a remarkably pristine world. You can ski across for days without seeing the horizon change. At first glance, it seems like a place untouched by people. But scientists have found parts of the Arctic ecosystem have been altered by climate change.
Rock Basin Lake on Ellesmere Island, Nunavut. Scientists predict climate change will be more pronounced in such northern areas. (Courtesy: John Smol)
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One problem is that the permafrost and glaciers are no longer permanent features of the landscape. In fact, the "land" of sea ice is melting and shifting underfoot.
Stories of chunks of ice breaking off and hunters disappearing make Shawn Marshall nervous.
"It's strange to be on sea ice," said Marshall, a glaciologist at the University of Calgary who studies the stability of the Greenland ice sheet. "Unnerving."
Sea ice cover
Marshall enjoys working in what he calls a "world of white," where he and his colleagues document the changes seen by northerners.
As Marshall collects his samples in a land of 24-hour sun, he's startled to find a hazy layer of smog more commonly found in Los Angeles. When he analyses ice samples, he sees a booming signal of pollutants like lead and sulphates that were spewed into the polar air during the Industrial Revolution.
Canadian scientists like Marshall are out in force across the vast tundra, drilling ice core samples, weighing furry critters and growing flowers as they attempt to understand the dramatic climate changes that are expected, and how today's greenhouse gas emissions are aggravating the problem.
Canada's Arctic offers a window on global warming. What's happening there now is a harbinger of what will happen to the rest of the hemisphere, researchers warn.
Ice cores offer one line of evidence. The columns of ice are a lot like tree rings. When researchers drill for ice cores, they can visually identify annual layers of accumulation, just as tree rings provide a record of local growing conditions during the life of a tree.
Things are changing, even at the frozen top of the world, east of Canada's Arctic islands. Marshall can feel the climate changing in his bones. Literally. The snow accumulation is different now, making the ice harder and more difficult for his team to dig through. As researchers try to access samples, their aching muscles testify to one of the effects of Arctic climate change.
In 1990, it was easier to pull up samples because the ice didn't melt as much during the summer, Marshall told CBC News Online. In contrast, cores from 1970s are almost purely snow with little refrozen ice.
Ice integrator
A gravity corer is used to collect lake sediment samples. (Courtesy: John Smol)
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While Marshall focuses on glaciers, Canada's Research Chair in Arctic System Science, Prof. David Barber of the University of Manitoba, studies sea ice – frozen water from the Arctic Ocean.
Sea ice responds to forces like wind from above and warming from the ocean below. Barber, along with doctoral student C.J. Mundy and the rest of their research team, use aircraft, ultra-light vehicles and submersibles to access their ice camps and conduct field research.
Meanwhile, from the vantage point of space, satellites show the frozen area is losing about 34,000 square kilometres per year on average. The ice is shifting from the type that lasts for years to a softer variety that survives only one summer.
Given the melting trend, sea ice cover will disappear as soon as 2050, meaning the summer will be free of ice altogether, Barber said. Observations and circulation models both support the projection, which already seems to be happening.
The melting will likely open up a northeastern sea route to cut travel times for ships between Russia and North America, followed by a clearing of the Northwest Passage through Canada's Lancaster Sound.
Fragile food chain
Arctic scientists say their studies show the ecosystem is being profoundly affected by climate change.
Diatom (Courtesy: Marianne Douglas)
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Unlike more complex ecosystems in the tropics, if one part of the Arctic is damaged, there are few alternatives available in the food chain.
Simple life like algae evolved to live in five to 25 centimetres of ice, which offers just enough light to grow. Too much sun and the photosynthetic life burns off, destroying the base of the food chain.
One step up the food chain, plants are showing changes, too. On Alexandra Fjord on Ellesmere Island, geography Prof. Greg Henry of the University of British Columbia has set up long-term warming experiments to see how plants on the tundra respond to up to three degrees of warming in the summer.
In the International Tundra Experiment, or ITEX, Arctic scientists from several countries are testing plots of greenhouses, using the same experimental setup, allowing results to be compared across the North.
After 15 years of research, Henry's team has found an increase in shrub cover right at the tree line around Inuvik, as well as in Alaska. In general, plants are flowering earlier, and their leaves are sprouting sooner.
Changes in snow distribution and increases in open water are also bringing more evaporation and precipitation to a region that isn't adapted to rain – the drops disintegrate the snow pack.
No part of the ecosystem will survive untouched. Further north, infrequent events like rainfall in late winter increasingly threaten entire populations of caribou.
A female hoary marmot. (Courtesy: David Hik)
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Mammals like ground squirrels and marmots, as well as birds such as geese, are also struggling with the stress of warming.
Prof. David Hik of the University of Alberta, who holds a Canada Research Chair in Northern Ecology, studies how herbivores are able to adapt to climate change.
A late spring storm can have a dramatic effect on vegetation, and highlight the razor-sharp balance between life and death in the Arctic. A two-week difference in snowmelt can translate into 20 per cent less food availability for herbivores, Hik said.
Hoary marmots, for example, are woodchuck-sized critters with silver-coloured fur that weigh up to eight kilograms. Normally, a female can successfully wean three offspring, but 30 days of snowmelt can reduce the survivors to just one young marmot.
Dall sheep ram (Courtesy: David Hik)
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Animals that can't migrate or hibernate try to use different strategies to adapt to their alpine habitat. Dall sheep will move up and down a mountain. But that's not an option for smaller mammals sharing tighter living quarters.
An adult may be able to stick out one bad year, but it can't compensate for many tough seasons. "It's the magnitude and trajectory of climate change that are the problem," Hik said.
Spring 2005 will be the 11th season Hik's returned to the alpine regions of the Yukon. Although the long days of sunlight energize the "happy, healthy field crews," they also have to be wary of rockslides and other mountain hazards as they work.
Unprecedented changes
In both the High Arctic and subarctic, photosynthetic algae called diatoms fix carbon for all animals.
Prof. John Smol takes a section of sediment to peer back into the history of a lake. (Courtesy: Marianne Douglas)
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As lakes fill, diatoms become preserved in the muddy sediments. Older organisms are found in deeper sediments, creating a timeline for scientists to use to reconstruct past environmental conditions.
By comparing the catalogue of fossilized diatoms in different time slices of sediment that have accumulated at the bottom of lakes, scientists can infer past conditions based on what species they find. Since some diatoms prefer lower temperatures or acidic habitats, if many cold-loving specimens are found then the area was likely once more frigid.
In the Arctic's short growing season, photosynthetic life like algae respond dramatically to extra light, habitats, and nutrients as the region warms.
Prof. John Smol of Queen's University in Kingston, Ont., and Prof. Marianne Douglas of the University of Toronto say they've seen unprecedented changes in the communities of diatoms found in the Arctic since the 1800s.
As Canada's Research Chair in Environmental Change, Smol's research helps reconstruct conditions before people began keeping records of temperature and water quality.
The patterns are consistent with recent warming in lakes across the Arctic, reflecting trends that are difficult to explain without factoring in human-induced climate warming. By looking back, researchers are able to find what conditions were like "before people started an uncontrolled experiment with the atmosphere," said Smol. "The case for climate change is in."
At the University of Victoria, Prof. Andrew Weaver agrees with Smol, saying, "The science is done." Now it's time for Canada to act on the policy, reducing greenhouse gases to below 50 per cent of 1990 levels as soon as possible, Weaver said.
Role of governments & industry
Weaver uses climate-modelling tools to compare past environmental conditions and the wealth of data on present-day climate to make future projections.
For underobserved locations, scientists turn to traditional knowledge to help fill in the gaps. People in southern Canada may not put much heed in stories of grandparents trudging through knee-deep snow to get to school. But scientists consider the oral tradition of elders to be much more reliable, Weaver said.
Information from elders guides scientists as they decide where to collect more data. If Inuit say they're collecting more driftwood at a certain spot, it helps scientists to determine circulation patterns and focus their measurements.
Weaver likens climate change research to sewing a quilt. "Different researchers in different fields make different squares of the quilt, like ice cores from Greenland, sediment cores from the North Atlantic, satellite measurements etc. Climate researchers pass the thread through all the squares to try and put the quilt together".
Documents like the Intergovernmental Panel on Climate Change are based on the work of modelling research groups around the world, which share their data.
By looking at what the models project, the report's authors can say what is likely to happen with varying degrees of certainty. Some projections, such as the opening of a sea route, are predicted with a high degree of statistical confidence.
Both Weaver and Smol dismiss those who doubt climate change is real, because they've been through similar debates before. Smol recalls the acid rain debate 15 years ago, when industries argued the acidity was part of a natural cycle.
Manufacturers may dismiss climate change research as "junk science" for now, but Weaver said they are developing alternatives, just as they did for ozone-depleting CFCs in the 1990s.
"It's junk science while there are no widgets," said Weaver. "Suddenly, it's true, once they have a widget."
That's why Weaver said he's cynical but optimistic that industry, rather than governments, will take the lead and respond to consumer pressure for alternatives to burning fossil fuels.
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