FIFTEEN thousand years ago, most of Canada was covered by a thick sheet of ice. Most of Canada is now covered by a thin sheet of ice for a few months annually after October.
The last great glacial age, from which we are just emerging, was one of four in the history of the Earth that defied the norm of much longer, warmer periods. Here's what the Encyclopedia Britannica says about the Earth's climate over time:
"Compared with the contemporary world climate, the climates of geological times were relatively warm, with few extremes of temperature. Polar latitudes were cool-temperate, with open seas and with little snow or ice to reflect solar radiation. The mid-latitudes were sub-tropical or warm-temperate, although the equatorial zone was probably no warmer than the modern one. It appears likely that the winter temperature gradient between latitudes 0 and 90 degrees North was comparable to that between 0 and 40 degrees North today. During these long inter-glacial periods of `normal' climate, it is likely that modern, summer-type circulation patterns were prevalent all year."
If the Earth is finally escaping the last ice age, it is warming toward what Britannica calls "normal" historical values (when dinosaurs inhabited lush Alberta). The forces at play are numerous and obviously profound. They include the amount of carbon dioxide (CO2) in the air, the amount of dust, the height of continents and the waxing and waning of glaciers themselves.
It is because many variables operate through complex systems -- and because the global climate has changed so radically without the historical presence of humans -- that we engage in such debate over the effect of humans on climate now. Fast, significant climate change would affect our interests greatly, but is it happening, and are human activities playing any serious part?
C02 levels have been increasing for 150 years, and the last decade or two have been warmer than earlier recent times (which include the cool 1950s and 60s, and the Little Ice Age in Europe between 1200 and 1700). Because C02 is a greenhouse gas, a direct correlation has been drawn between its man-made increase in the atmosphere and global warming -- with attendant fears of rising sea levels, droughts, storms, disease and mass migrations of peoples.
But the science on this is extremely tentative, both in theory and observation. Nothing has happened to the global climate in the past 150 years, including the cool decades, that falls outside the margin of observed variability over the past several thousand years. The implications for surface temperatures of increasing C02 at higher elevations is not scientifically established. The closest scientists have come to a consensus about C02 and global warming is the famous phrase that "the balance of evidence suggests" human activity may have some effect on surface temperatures over time. There is no broad scientific support for the popular assumption that greater extremes of weather are tied to purported global warming.
And yet, enough agreement exists among some scientists and politicians in industrial countries to have precipitated several international agreements to reduce the growth rate of C02 at substantial risk to economic growth. Depending on where you stand on the science of global warming, these agreements demonstrate either wise humility in the face of a fragile planet or manic hubris about mankind's significance in the greater order of things. (Or maybe they just demonstrate careless political opportunism.)
The 1993 Rio Treaty called for stabilization of C02 emissions at 1990 levels among industrial countries by 2000 -- a target that will not be met, and excludes the developing nations.
Last December, the Kyoto Protocol proposed to strengthen that commitment, with binding C02 reduction targets among industrial nations only, to be met by 2012. The United States promised a reduction of 7 per cent below 1990 levels, and Canada 6 per cent. Some analysts say this would require a reduction of 50 per cent per capita in the C02 emissions that would, save for Kyoto, have occurred in North America in 2012. (Even so, global C02 concentrations would continue to rise smartly.)
The Kyoto Protocol must be ratified by at least 55 nations, including countries accounting for 55 per cent of the industrial countries' emissions. If Kyoto is ratified, legislation will follow that could include significant disincentives to fossil-fuel consumption, which could affect the demand for everything from drilling rigs to the steel that goes into cars and trucks. Many industrial processes that emit C02 would be discouraged, and some of those industries would shift to developing countries where no limits apply. Economic growth in North America would be dampened, unemployment would rise and incomes would lag behind their current potential.
Governments sometimes resort to doubtful science to escape difficult political decisions. The mystery is why governments are resorting to doubtful science now to embrace them.
(This column draws on a panel discussion at the American Iron and Steel Institute general meeting in Toronto on May 21.)
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