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∙ Whatever the cause of current weather patterns, they cannot yet be related to any of the long-range cooling —or warming—trends foreseen by scientific Cassandras. Says George Kukla, a climatologist at Columbia University's Lamont-Doherty Geological Observatory: "Just because we can't get our cars started, are suffering from frostbite, and have a few feet of snow in our driveways, we should not start worrying about an Ice Age." Among scientists who fear that significant worldwide climatic changes have already begun, there are those who believe that another Ice Age is not far ahead—as well as others who predict that a potentially devastating warming trend may occur.
Ice Age doomsayers note evidence that average temperatures in the Northern Hemisphere dropped 1° Celsius during the 1950s and 1960s. Kukla found that the average snow and ice cover in the Northern Hemisphere increased sharply in 1971 compared with the years between 1967 and '70. It reached a peak in '72 and '73 and then retreated about halfway back to what it had been in the late '60s. Now, says Kukla, satellite studies indicate that the snow and ice cover last fall increased again to about the level of '71. German Oceanographer Martin Rodewald has noticed a slow, general cooling of the waters of the North Atlantic and North Pacific and an air-temperature drop in the Arctic regions over Canada and Russia.
Global cooling might be explained by a link between ice ages and changes both in the earth's attitude and in its orbit around the sun. That concept was championed by Germany's Alfred Wegener (best known for his ideas about continental drift) and later refined by Yugoslav Mathematician Milutin Milankovitch, for whom the theory is now named. Last year three scientists —James Hays of Columbia, John Imbrie of Brown University and Nicholas Shackleton of Cambridge University in England—published the strongest evidence yet that Milankovitch was right. Analyzing cores of sediments taken from beneath the floor of the Indian Ocean, the trio assembled an accurate record of the earth's climate dating back 450,000 years and correlated this information with data about the earth's orbit.
Their finding: the timing of each of the planet's major ice ages was closely related to changes in the earth's attitude and orbit that reduced the amount of summer sunlight striking the polar caps. Unless man somehow unbalances the equation, these scientists concluded, the trend over the next 20,000 years will be toward a cooler global climate and the spread of glaciers in the Northern Hemisphere—a new Ice Age.
The consequences could be catastrophic. A worldwide average temperature drop of only 1° Celsius could shorten growing seasons in the temperate zones enough to threaten global food supplies. Increased heating requirements would further strain energy resources such as coal, natural gas and oil.
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