by Bruce Cherney (Part 2 of 2)
Carbon dioxide actually helps keep the polar ice caps in check. Without the balance provided by just the right mix of greenhouse gases, the ice would inexorably spread outward to engulf the rest of the world.
The earth’s climate is controlled by the interaction of solar radiation on the surface and atmosphere. While some of the radiation is reflected off clouds and the earth’s surface back into space, about two-thirds is absorbed by the earth’s surface and atmosphere. As the sun takes its annual trek southward, the snows arrive in Manitoba and the white surface of the land reflects more of this life-giving energy back into space, intensifying the cold of winter which is called the albedo effect.
The last Ice Age became a thing of the past when a warming interval occurred. Actually, the climate changed with such frequency that long periods of cold were interspersed with long periods of warmth.
James Lovelock, author of The Revenge of Gaia (Mother Earth in Greek mythology), said some time in the next 100 years it’s going to get hotter and hotter and hotter, according to a report in the British newspaper The Telegraph.
He claims that billions will die and civilization will degenerate into a “broken rubble ruled by warlords.”
Lovelock predicts Europe will be 8°C warmer than today, and there’s nothing that can be done to stop the rapid temperature rise — not the Kyoto protocols or closing down all the world’s industries.
A recent conference of scientists in St. Louis further concluded that greenhouse gases are being released 30 times faster than the rate of emmissions that triggered a period of extreme global warming — a rise of 5°C — 55 million years ago. The gases were released during a 10,000 year period. If the present trend continues, the scientists say the level of warming reached 55 million years ago will be reached within 300 years.
Despite all these dire predictions, the world and human species have survived wild temperature flucuations in the past.
About 140,000 years ago (when Home sapiens sapiens [modern man] and Homo sapiens neanderthalis [Neanderthal man] were evolving in Africa and Europe, respectively), the globe was 6°C colder than it is today. Then 130,000 years ago, there was a rapid rise in the temperature until about 114,000 years ago, when it was 1°C or 2°C warmer than today. Then over the course of 400 years, there was a rapid switch in the climate and the last Ice Age, called the Wisconsin in North America, commenced.
From about AD 1300 to the 1850s, the earth was experiencing what has been termed the Little Ice Age. But, this had been preceded by balmy weather which had a direct effect on human migration from the northern regions of Europe. Higher temperatures in northern Europe meant more crops and a population expansion. The result was the Viking Age of raids, exploration and settlement by Norse in Greenland, Newfoundland, Russia, Iceland, Ireland, England, Scotland and France.
Without the rise in temperatures, there is no reason to assume that Eric the Red could have established a colony in Greenland. In fact, the coming of the Little Ice Age also meant that this colony was doomed — crops and livestock that the settlers relied upon died in the cold snap. The settlers were also under pressure from the better cold-weather adapted Inuit arriving in the region.
The first colony to fall was the Western Settlement in 1349. The Eastern Settlement lasted for another 100 years. By the about 1450, all the Norse settlers had perished.
The last recorded mention of the settlers by a European visitor to Greenland was in 1408. Seafarers in the 1500s passing by Greenland reported that there were only ruins on the island where there had once been Norse colonies.
“Thys yere was the grete frost and ise,” a Londoner wrote in 1410 (Middle English is the term used for the language), “and the most sharpest wenter that ever man sawe, and it duryd fourteen wekes so that men might in divers places goo and ryde over the Temse (Thames River).”
“Our years are turned upside down,” reported the English priest John King in 1595, “our summers are no summers; our harvests are no harvests.”
Even during the Little Ice Age, there was an intermediate period of warming starting in 1450 and ending 100 years later, and then the cold continued for another 300 years.
Over the past 15,000 years, the global climate has been subjected to some rather rapid changes. There was a rapid temperature increase over the course of decades with the end of the last Ice Age, increasing the global temperature by about 5°C.
The rise was evident until about 12,900 years ago when the earth’s temperature suddenly took a nose dive during what is called the Younger Dryas event.
The sudden drop in temperatures, especially in North America, has been attributed to a number of sources, but the one gaining the most ink was the abrupt breaking of ice dams holding back glacial lakes. When the dams broke, cold water flowed into the ocean in massive volumes. The result of these infusions of cold water was a disruption of the warmth-bearing ocean currents which originate in the southern Atlantic.
The surface currents of the Atlantic act like conveyor belts, carrying warm, salty water from the tropics to the temperate regions. The water cools in temperate North America and then becomes dense enough to sink and send heat into the atmosphere. If the currents are disrupted by an infusion of cold freshwater, the conveyor belts no longer send normal amounts of heat into the atmosphere of northern regions.
Glacial Lake Agassiz at its fullest extent between 9,900 and 9,500 years ago covered much of Manitoba and portions of Saskatchewan, Northern Ontario, North Dakota and Minnesota.
At its peak, Lake Agassiz covered over 500,000 square kilometres and was the largest freshwater lake in North America. Throughout its 4,500-year history, the lake increased and decreased in water volume. Depending upon the extent of the ice, Lake Agassiz either drained into the Minnesota River and then into the Mississippi River and finally into the Gulf of Mexico, eastward into the Great Lakes Basin or northward into Hudson Bay.
With the retreat of the ice, Lake Agassiz drained to the east into the St. Lawrence Seaway which had opened up near Newfoundland. But when the cold intensified, the ice again advanced down to Minnesota and the lake was blocked once again.
The greatest escape of water came about 8,200 years ago when ice dams broke and high volumes of cold water flowed into the Atlantic, disrupting the North American climate for about 100 years.
It was a theory first proposed by University of Manitoba geologist Jim Teller and recently confirmed by NASA scientists. Teller, along with colleagues at the Geological Survey of Canada and the University of British Columbia, had no direct evidence, but said in a 2003 study in the journal Science, that the breaking of the Lake Agassiz ice dams resulted in the sudden flow of cold, freshwater into Hudson Bay and beyond, disrupting the warm current in the Atlantic.
The article said when the ice dam burst it spilled 162,000 cubic metres of freshwater into the ocean.
NASA scientists tested Teller’s theory with the geological record and simulated the effect of what would happen in the event of a massive influx of Lake Agassiz water into the North Atlantic. They found that the event would drop temperatures in the North Atlantic and Europe by 2°C, creating a mini-Ice Age for 50 to 150 years.
The scientists said the Lake Agassiz event was so rare that they coined it “A Goldilocks event” — an event with special factors that add up to form a unique scientific combination to unlock new mysteries.
The break in the ice dams resulted in the coldest climate event in the last 10,000 years.
Just as there was a cold spell during the Holocene, which is the period between the end of the Ice Age to the present, there was a time of intense warming which has been called the Altithermal.
The Altithermal lasted from about 7,000 to 5,000 years ago. Its unique aspect was that the temperatures were generally warmer than today but only in the summer and only in the northern hemisphere. This has been attributed to an increase in solar radiation caused by a shift in the earth’s orbit, with temperatures being between 1°C and 4°C warmer than today, depending upon the region in the Northern Hemisphere.
Within Manitoba, the climate warmed enough that the treeline expanded 240 kilometres north of the present forest limit. In southern Manitoba, deciduous trees moved further north, marking the initial occurrence of Aspen Parklands.
At this time, Lake Manitoba had dried to the point where it became kilometres of mudflats and gravel banks dotted with brackish ponds. This situation reigned for about 1,000 years until gradual changes refilled the lake to its present level.
“Personally, I don’t think it was a thousand years of continual drought (at the Altithermal’s height),” Leo Pettipas, a Manitoba archaeologist, earlier told the WREN. But, he added that the droughts would have been more frequent and more severe than anything today.
The archaeologist said the droughts can be partially compared to the conditions of the Great Depression when soil was blown throughout the countryside, although the duration of these conditions would have been much longer during the Altithermal.
“Manitoba was a have-province in those days,” Pettipas commented. “The Great Plains and the Dakotas area (in the U.S.) were less attractive during the Altithermal.
“Human beings suffering from drought, sought refuge in the more attractive areas such as in southern Manitoba where there were rivers and springs and lake regions.”
Basically, human habitation occurred along the fringes of the drought. Humans moved from the grasslands into the forests where water and shelter could be found.
Native cultures that occupied Manitoba from the time that the ice began to retreat showed a great ability to adapt to changing climate conditions, neither severe cold nor drought brought on by warm weather deterred them.
Allen Trychniewicz, of the Winnipeg-based International Institute for Sustainable Development, said in a report that with climate change, summers are expected to be seven to eight degrees warmer within 30 to 50 years on the Prairies.
The result will be wheat farming about 200 kilometres further north than today. In the southern region of the province, crops that had been impossible to grow before would be able to thrive.
If the mean average temperature rises by just 3°C, temperatures in southern Manitoba would be similar to those experienced in South Dakota, and The Pas would have a climate similar to Winnipeg’s today.
According to a CP report last week, Louis Fortier, a researcher from Laval University in Quebec City who was part of the recent study with Barber, said Arctic ice is no longer safe to travel upon, houses are being washed away as shorelines erode as much as six metres a year, and food sources such as caribou and seals could eventually disappear and be replaced by other species in the next century.
Scientists, according to Yahoo News, are predicting that the summertime Arctic will be ice-free by the end of the century, threatening the existence of polar bears, a marine mammal that depends upon the ice to live.
Manitoba researchers are also reporting that the polar bears at Churchill are being adversely affected by climate change. With the warmer temperatures being experienced, polar bears are having to wait longer for Hudson Bay to freeze over so they can go out on the ice to hunt seals. The result is that the bears are consuming less calories each hunting season and thus their dietary requirements are not being met. If the present situation continues, the bears will starve to death in great numbers.
At this time, it is extremely difficult to determine the effect of manmade agents’ contribution to climate change as well as who is right about the fate of the earth. Some climatologists are now saying that it will take 20 years of intense investigation before unambiguous results can be attained.
The only examples that can now be used to guide predictions are what has happened in the past, and the evidence shows that climate is far from stationary — there have been wild temperature fluctuations throughout the earth’s history.