Just as last week's tremors were destroying highways, buildings and lives in Southern California, an even deadlier natural disaster was advancing slowly but inexorably south from Canada into the U.S. By midweek a huge mass of frigid arctic air had practically paralyzed much of the Midwest and East. Temperatures in dozens of cities dropped to all-time lows: -22 degreesF in Pittsburgh; -25 degrees in Akron, Ohio, and Clarksburg, West Virginia; -27 degrees in Indianapolis, Indiana. Chicago schools closed because of cold weather for the first time in history, Federal Government offices shut down in Washington, and East Coast cities narrowly escaped widespread power outages as overburdened electric utilities struggled to keep homes heated. Hundreds of motorists in New Jersey had to be rescued by snowmobile from an impassably icy highway, and thousands of the homeless crammed into New York City's shelters to avoid freezing. By week's end the unprecedented cold wave had killed more than 130 people.
What ever happened to global warming? Scientists have issued apocalyptic warnings for years, claiming that gases from cars, power plants and factories are creating a greenhouse effect that will boost the temperature dangerously over the next 75 years or so. But if last week is any indication of winters to come, it might be more to the point to start worrying about the next Ice Age instead. After all, human-induced warming is still largely theoretical, while ice ages are an established part of the planet's history. The last one ended about 10,000 years ago; the next one -- for there will be a next one -- could start tens of thousands of years from now. Or tens of years. Or it may have already started.
There is no way of knowing yet: an entire winter of record-shattering cold, let alone a single week, might be a meaningless blip in the overall scheme of long-term climate trends. In fact, last week's cold wave was caused by a phenomenon that is by no means rare. The jet stream, a stratospheric wind that governs the movement of air over North America, dipped temporarily south of its usual course. As it did so, the stream pulled along a vast high-pressure system from Siberia and the Arctic Ocean.
If that starts happening more and more often, though, it might mean that something bigger is going on. Climatologists once thought the world eased into ice ages, with average temperatures in parts of the Northern Hemisphere falling 15 degrees over hundreds or thousands of years. During long, frigid winters and short, cool summers, snow piled up much faster than it could melt, and mile-thick sheets of ice gradually covered much of the planet's land surface. After 100,000 years or so, scientists believed, the glaciers made a dignified retreat, stayed put for about 10,000 years and then began to grow again.
But over the past several years, researchers have dug deep into Atlantic sea-floor sediments and Greenland glaciers to study the chemistry of ancient mud and ice, and they are increasingly convinced that climate change is anything but smooth. The transition from warm to frigid can come in a decade or two -- a geological snap of the fingers. Says Gerard Bond, a geophysicist at Columbia University's Lamont-Doherty Observatory: "The data have been coming out of Greenland for maybe two or three decades. But the first results were really so surprising that people weren't ready to believe them."