Focus on global warming 课文原文(8页).doc
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1、-Focus on global warmingTwenty-five years ago if you made a trip to the local library and perused the periodical section for articles on global warming, youd probably have come up with only a few abstracts from hardcore science journals or maybe a blurb in some esoteric geopolitical magazine. As an
2、Internet search on global warming now attests, the subject has become as rooted in our public consciousness as Madonna or microwave cooking.Perhaps all this attention is deserved. With the possible exception of another world war, a giant asteroid, or an incurable plague, global warming may be the si
3、ngle largest threat to our planet. For decades human factories and cars have spewed billions of tons of greenhouse gases into the atmosphere, and the climate has begun to show some signs of warming. Many see this as a harbinger of what is to come. If we dont curb our greenhouse gas emissions, then l
4、ow-lying nations could be awash in seawater, rain and drought patterns across the world could change, hurricanes could become more frequent, and El Ninos could become more intense.Our Warming Planet What has worried many people now is that over the past 250 years humans have been artificially raisin
5、g the concentration of greenhouse gases in the atmosphere. Our factories, power plants, and cars burn coal and gasoline and spit out a seemingly endless stream of carbon dioxide. We produce millions of pounds of methane by allowing our trash to decompose in landfills and by breeding large herds of m
6、ethane-belching cattle. Nitrogen-based fertilizers, which we use on nearly all our crops, release unnatural amounts of nitrogen oxide into the atmosphere. Once these carbon-based greenhouse gases get into the atmosphere, they stay there for decades or longer. According to the Intergovernmental Panel
7、 on Climate Change (IPCC), since the industrial revolution, carbon dioxide levels have increased 31 percent and methane levels have increased 151 percent. Paleoclimate readings taken from fossil records show that these gases, two of the most abundant greenhouse gases, are at their highest levels in
8、the past 420,000 years. Many scientists fear that the increased concentrations of greenhouse gases have prevented additional thermal radiation from leaving the Earth. In essence, these gases are trapping excess heat in the Earths atmosphere in much the same way that a windshield traps solar energy t
9、hat enters a car. Much of the available climate data appear to back these fears. Temperature data gathered from many different sources all across the globe show that the surface temperature of the Earth, which includes the lower atmosphere and the surface of the ocean, has risen dramatically over se
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