Goodbye La Nina, Hello Polar Pig.

Short term weather extremes not indication of global warming.

Published: 07-Dec-2000

After a series of mild winters, the Canadian climate has launched a surprise attack.

No one predicted the recent spell of severe sub-zero weather which has sent natural gas prices soaring and sparked fears of fuel shortages in the United States.

The federal Environment Department's state-of-the-art weather-forecasting program had actually projected this winter would be warmer than normal.

Far from invalidating worries about climate change, the current blast of Arctic chill fits into a picture of increasing weather instability caused by human influence, environmentalists say.

``What we're seeing overall is dramatic changes in temperature, from very warm to very cold and back to very warm,'' says Greenpeace campaigner Steven Guilbeault as he shivered on an Ottawa street.

Guilbeault and fellow activists were demonstrating outside a hotel where international negotiators were trying to salvage a global treaty to cut greenhouse emissions.

The meeting ended inconclusively on Thursday, symbolizing the immense difficulty that modern societies are having to deal with an issue which has consequences for virtually every sector of the economy.

Environment Minister David Anderson says Canada is already being affected by climate change - he cited the melting of Arctic ice - and remains keen on getting an agreement.

Climate trends can't be assessed by short-term weather patterns such as the current cold, he notes.

``There will inevitably be spikes and troughs. You cannot judge by a particular instance at a particular time. You have to get long-term trend data.''

Scientists say that greenhouse gases such as carbon dioxide are transparent to incoming solar radiation, but opaque to that radiation when it bounces back from Earth at a shorter wavelength.

The result is that solar energy is trapped in the atmosphere instead of being reflected into space.

Levels of cardon dioxide, largely produced by the burning of fossil fuels, have been rising since the industrial revolution and global temperatures have risen by more than a degree at the same time. Statistics suggest winters have been getting milder on average.

Last year, Edmonton had its warmest December in 119 years, Ottawa's Rideau Canal skating rink was slush, Quebec ski hills were losing money and the Maritimes had green grass in January.

But the science of global warming remains controversial and public opinion remains confused, in part by the seeming contradiction of intense cold snaps.

David Phillips, senior climatologist with the Environment Department, says he had never heard the term ``polar pig'' - meaning a surge of air from the Arctic polar region - until last week.

He says the term was coined by a U.S. commodities trader and concedes the current cold spell is beastly no matter what term is used.

The department's 10-day forecast calls for temperatures 4.0 to 4.5 degrees lower than normal from Vancouver to St. John's, Nfld.

``That doesn't seem like a lot, but spread over 10 days that is enormous,'' says Phillips.

He admits the department's long-range forecast for a mild winter is somewhat embarrassing.

``This is a forecast which is issued by a computer, there's no human intervention. And then it's left to us to explain it. Well, we're scratching our heads.''

He says that Canada's weather in the last few years has been dominated by west-to-east flows from the warm Pacific.

Those westerly flows have been attributed to the El Nino-La Nina phenomenon - a current of warm water in the Pacific Ocean that has been gaining strength in recent decades.

Canada now may be seeing a return to a more traditional patterns, with weather moving from north to south.

Heather Auld, a federal meteorologist, says the disappearance of El Nino-La Nina probably increases the chances of a cold winter in Western Canada and in the northern part of Central Canada.

But it's hard to be sure of cause and effect because the weather has always been changeable, she notes.

The big problem for scientists has been to establish the irrefutable ``signal'' of climate change over the ``noise'' of natural variability. The sheer complexity of the science can be overwhelming.

For example, a just-published study by a University of Ottawa geologist Jan Veizer suggests there was no correlation between levels of carbon dioxide and climate over much of prehistoric time.

Some have interpreted the study as a blow to the basic assumptions about global warming. Minister Anderson says that's not the case.

``All of these things are subject to certain error, many of them are hypotheses, but you get a general trend of opinion which is overwhelmingly that CO2 is important.''

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