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, a

17、nd oil, and deforestation. To reduce the emission of heat-trapping gases like carbon dioxide, methane, and nitrous oxides, we can curb our consumption of fossil fuels, use technologies that reduce the amount of emissions wherever possible, and protect the forests in the world. We can also do things

18、to mitigate the impacts of global warming and adapt to those most likely to occur,9 e.g., through careful planning and other strategies that reduce our vulnerability to global warming. But we cant stop there. We are also advocating policies that will combat global warming over the long term, things

19、like clean cars that run on alternative fuels, environmentally responsible renewable energy technologies, and stopping the clear-cutting of valuable forests. Clearly, global warming is a huge problem. It will take everyone governments, industry, communities and individuals working together to make a

20、 real difference. Fortunately you can be part of them. 關(guān)注全球氣候變暖二十五年前，如果你想去當(dāng)?shù)氐膱D書館通過各種期刊搜索關(guān)于全球氣候變暖的文章的話，很可能你只能找到一些刊登在核心自然科學(xué)期刊或非常專業(yè)的地理科學(xué)雜志上的同類文章的摘要。然而，當(dāng)今因特網(wǎng)搜索結(jié)果表明全球氣候變暖，就像麥當(dāng)娜或微波爐一樣，成為所有人都十分關(guān)心的話題。應(yīng)該說公眾對全球氣候變暖的關(guān)注是很有必要的。除了一些可能的巨大災(zāi)害，例如新的世界大戰(zhàn)、巨型小行星撞擊地球、或是無法治愈的流行疾病等等，全球氣候變暖可能是對地球的唯一最大威脅。近幾十年來，人類的工廠和汽車向大氣中排放了

21、數(shù)十億噸的溫室氣體，全球氣候已經(jīng)表現(xiàn)出了變暖的趨勢。許多人認(rèn)為這是災(zāi)難即將來臨的不祥征兆。如果我們不再抑制溫室氣體的肆意排放，那么那些海拔很低的國家可能被海水淹沒，同時多雨和干旱地區(qū)的分布也會發(fā)生變化，颶風(fēng)將愈加頻繁，而“厄爾尼諾”現(xiàn)象也會愈演愈烈。地球正在變暖現(xiàn)在令大多數(shù)人擔(dān)憂的是在過去250年中人類已經(jīng)人為地增加了大氣中溫室氣體的濃度。我們的工廠、發(fā)電廠、汽車燃燒煤和汽油，排放出無窮盡的二氧化碳。我們?nèi)斡衫趶U渣填埋池里分解產(chǎn)生甲烷，還大量飼養(yǎng)胃里會產(chǎn)生甲烷氣體的家畜，就這樣我們?nèi)藶橹圃炝藬?shù)百萬噸的甲烷氣體。我們幾乎在所有的農(nóng)田中都使用以氮為主要元素的化肥，導(dǎo)致超過正常數(shù)量的氧化氮進(jìn)入大

22、氣之中。一旦這些以碳為主要元素的溫室氣體進(jìn)入大氣層，它們就會存在幾十年甚至更久。根據(jù)政府間氣候變化問題專門研究小組的研究結(jié)果，自工業(yè)革命以來，空氣中二氧化碳的含量增長了31%，甲烷氣體的含量甚至增長了151%。從古代化石記錄中得到的地質(zhì)氣候資料顯示,這兩種含量最多的溫室氣體(二氧化碳和甲烷)居過去42萬年之首。許多科學(xué)家擔(dān)心溫室氣體濃度日益增長會阻礙地球多余熱量的散發(fā)。實際上，這些氣體已經(jīng)在阻礙地球大氣中多余熱量的散發(fā)，它們阻礙熱量散發(fā)的原理就和汽車擋風(fēng)玻璃阻礙太陽熱量進(jìn)入車廂是一樣的。大量可獲得的氣候數(shù)據(jù)證明人們的擔(dān)憂是很有道理的。從全球各地搜集的氣溫數(shù)據(jù)顯示地球表面溫度，包括較低大氣層和海洋表面溫度，在過去幾十年間劇烈上升。全球海平面測量數(shù)據(jù)也表明在上個世紀(jì)中，海平面上升了0.10.2米，也就是說海水溫度每4000年上升大約1。冰川研究數(shù)據(jù)也顯示全球大陸冰川正在逐步消融。總而言之，以上這些數(shù)據(jù)都表明在過去一個世紀(jì)中，地球表面溫度上升是近1000年里最快的。很自然地，許多科學(xué)家推測這種種氣候變化很可能會導(dǎo)致天氣越來越熱，涼爽的日子越來越少。根據(jù)政府間氣候變化問題專門研究小組的研究，地表夏季溫度上升幅度將遠(yuǎn)大