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1、Unit 8 Focus on Global WarmingJohn Weier Twenty-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
2、 magazine. As an Internet search on global warming now attests, the subject has become as rooted in our public consciousness as Madonna2 or microwave cooking.1 Perhaps all this attention is deserved. With the possible exception of another world war, giant asteroid, or an incurable plague, global war
3、ming may be the single largest threat to our planet.2 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.3 If we dont curb our greenhouse g
4、as emissions, then low-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 bee
5、n artificially raising 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 bree
6、ding large herds of methane-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 In
7、tergovernmental Panel 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 thei
8、r highest levels in 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
9、traps solar energy that enters a car.4 Much of the available climate data appear to back these fears.5 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 rise
10、n dramatically over several decades. Worldwide measurements of sea level show a rise of 0.1 to 0.2 meters over the last century. Thats an increase of roughly 1 every 4,000 years. Readings gathered from glaciers reveal a steady recession of the worlds continental glaciers. Taken together, all of thes
11、e data suggest that over the last century the planet has experienced the largest increase in surface temperature in 1,000 years. Not surprisingly, many scientists speculate that such changes in the climate will probably result in hotter days and fewer cool days.6 According to the IPCC, land surface
12、areas will increase in temperature over the summer months much more than the ocean. The mid-latitude to high-latitude regions in the Northern Hemisphere areas such as the Continental United States, Canada, and Siberia will likely warm the most. These regions could exceed mean global warming by as mu
13、ch as 40 percent. As far as human health is concerned, those hit hardest will probably be residents of poorer countries that do not have the funds to fend against changes in climate.7 A slight increase in heat and rain in equatorial regions would likely spark an increase in vector-borne diseases suc
14、h as malaria. More intense rains and hurricanes could cause more severe flooding and more deaths in coastal regions and along riverbeds. Even a moderate rise in sea level could threaten the coastlines of low-lying islands such as the Maldives. All across the globe, hotter summers could lead to more
15、cases of heatstroke and deaths among those who are vulnerable, such as older people with heart problems. The warmer temperatures may also lead to higher levels of near-surface ozone from cars and factories, which would likely cause more perilous air quality days and hospital admissions for those wit
16、h respiratory problems. Taking Actions Fortunately, we can take actions to slow down global warming.8 Global warming results primarily from human activities that release heat-trapping gases and particles into the air. The most important causes include the burning of fossil fuels such as coal, gas, and oil, and deforestation. To reduce the emission of heat-trapping gases like carbon dioxide, methane, and nitrous oxides, we can curb our consu
