A NEW ICE AGE
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 suprising that people weren’t ready to believe them.”
There is a growing understanding as well that ice ages are not uniformly icy, nor interglacial periods, i.e., periods between ice ages, unchangingly warm. About 40,000 years ago, for example, right in the middle of the last ice age, the world warmed briefly, forcing glaciers to retreat. And while the current interglacial period has been stably temperate, the previous one, according to at least one study, was evidently interrupted by frigid spells lasting hundreds of years. If that period was more typical than the present one, humanity’s invention of agriculture, and thus civilization, may have been possible only because of a highly unusual period of stable temperature – a fluke.
Just 150 years ago, the notion that much of the Northern Hemisphere had once been covered by thick sheets of ice was both new and highly controversial. Within a few decades, though, most scientists were convinced and began looking for explanations. Several suggested that astronomical cycles were involved, and by the 1930’s the Yugoslav astronomer Milium Milankovitch had constructed a coherent theory.
The ice ages, he argued, were triggered by changes in the shape of the earth’s slightly oval orbit around the sun and in the planet’s axis of rotation. Studies of the chemical composition of ocean-floor sediments, which depend on climatic conditions when the material was laid down, more or less supported Milankovitch’s predicted schedule of global glaciation.
According to Milankovitch’s cycles, an ice age could start sometime within the next 1,000 or 2,000 years. But geophysicists have realized for years that while the cycles are real and influence climate, they alone cannot explain ice ages. For one thing, Milankovitch’s timing of glaciation may be broadly correct, but major glacial episodes happen when his cycles call for minor ones, and vice versa.
A NEW ICE AGE (2)
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 U.S. cities dropped to all-time lows: -30°C in Pittsburgh; -32°C in Akron, Ohio, and Clarksburg; -33°C in Indianapolis. 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 cuts due to the overuse of electric utilities to keep homes heated. Hundreds of motorists in New Jersey had to be rescued by snowmobile from an impassably icy highway, and thousands of 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. Whatever 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.
A. Find the words which mean the same as the following.
1. approaching (paragraph 1):
2. almost, not completely (paragraph 1):
3. not done or known before (paragraph 1):
4. cause something to increase (paragraph 2):
5. sign (paragraph 2):
1. Which U.S. city had the lowest temperature?