FORECAST: UNSETTLED WEATHER AHEAD

After carefully studying woolly bear caterpillars, the thickness of fur on squirrels' tails and other natural signs, "Abe Weatherwise" late last year predicted in The Old Farmers'Almanac that the current winter would be a cold one. Jerome Namias, a meteorologist at California's Scripps Institution of Oceanography, had made a similar forecast. But even Namias is surprised at the subfreezing temperatures that have prevailed over most of the eastern half of the U.S. Says he: "I was a little too conservative. Our forecast was for the coldest winter in perhaps 20 years, but it now looks as if it is proving to be even colder than that. In many locations, 75-year-old records are going to be broken before the winter is over."

Namias and other meteorologists agree on the immediate reason for the bitterly cold weather. The high-level westerly winds--including the jet stream--that whistle through the upper atmosphere high above the U.S. have been circulating in an unusual pattern. Normally in winter these winds flow more directly across the country from west to east. This winter they are cutting across the Rockies much farther to the north than usual and then, as they head toward the East Coast, dipping much farther south than normal.

The product of that unusual pattern is this winter's wild weather. According to Namias, the jet stream has been picking up Pacific storms and guiding them across the U.S., "pepping up" each one as it crosses the country. The resulting heavy snowfalls that have accumulated on the ground in Eastern states further refrigerate Arctic air as it moves down from Canada. The snow covering also contributes to the dramatic difference between land and water temperatures, which in turn stimulates more storms along the East Coast--including the nor'easters that have been battering oil tankers. All the while, Western states have remained relatively unscathed. Says John Firor, executive director of the National Center for Atmospheric Research in Boulder, Colo.: "This year winter seems to have become stuck east of the Rockies."

What triggered these changes, however, remains unclear. Namias notes that water temperatures in the Pacific rose a few degrees higher than normal last fall off the west coast of North America, while dropping off in midocean. He believes that these temperature shifts influence the winds and determine the course of storms that work their way up to the jet-stream level. Harry Geise, a California meteorologist, blames the storms and frigid temperatures on a high-pressure zone of warm air hovering off the country's Pacific coast and sometimes shifting over land.

sb 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 1DEG 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 1DEG 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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Other scientists believe that the earth is actually getting warmer. As they see it, the cooling trend of the '50s and '60s has leveled off and worldwide temperatures are rising. As evidence, they point to uncharacteristically mild winters during recent years in Scandinavia and, with the exception of this year, in New England. Temperatures in Australia and New Zealand as well as Antarctica have risen slightly. Glaciers in the Alps have retreated slightly, and temperatures measured at 40 scattered points in the middle latitudes of North America have either stayed the same or risen during the past six years.

If a warming trend is indeed under way, many scientists say it probably has been caused by increasing amounts of carbon dioxide (CO2) spewed into the atmosphere by the burning of coal and petroleum products. While the CO2 does not prevent solar radiation from reaching the earth, it blocks the escape into space of heat rising from the earth's surface--the so-called greenhouse effect.

To those shivering through the current winter's chill, that prospect has a certain appeal. But a global warming trend could be just as disastrous as a worldwide freeze. More than a modest rise in temperatures could melt polar ice caps, cause extensive coastal flooding, drastically alter air circulation and rainfall patterns, and cut the productivity of many important agricultural areas.

Only time and more research will reveal which, if either, of these scenarios is correct. But whatever the long-term forecast may be, scientists do agree on one thing: earth's climate is entering a period of increased variability in which weather patterns are likely to fluctuate far more dramatically than they have in the past few decades. Geise believes next winter's weather will be the reverse of the present pattern. His forecast should come as welcome news to the Southeastern U.S.--which would get warmer weather--and as a mixed blessing to the Mississippi and Ohio valleys, which may get too much rain. Californians may have less to be thankful for. They are likely to experience temperatures next winter as uncomfortable for their area as this year's readings are for the beleaguered East.

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