A Strong Greenhouse Gas
1.Methane is a colorless,odorless gas;it is also a potent greenhouse gas,and once released into the atmosphere,it absorbs heat radiating from Earth's surface.That.s why methane is a major contributor to the planet's increasing temperature rise—or global warming.Molecule for molecule,methane.s heat-trapping power in the atmosphere is 21 times stronger than carbon dioxide,the most abundant greenhouse gas.
2.With 13 billion cows belching almost constantly around the world(100 million in the U.S.alone),it's no surprise that methane released by livestock is one of the chief global sources of the gas.Other prime methane sources： petroleum,drilling,coal mining,solid-waste landfills and wetlands.
3.Greenhouse gases like methane and carbon dioxide make up only a small part of Earth's atmosphere,which is 78 percent nitrogen and nearly 21 percent oxygen.And without greenhouse gases to trap the sun.s heat and warm the planet,life was we know it couldn't exist.But in the last 200 years,human activity that requires burning oil,natural gas,and coal for energy has magnified the greenhouse effect.
4.Atmospheric concentrations of methane have more than doubled in the last two centuries.Blame for this often focuses on big industries and gas-guzzling vehicles.But agriculture plays a major role,too.In the past 40 years alone,the global cattle population has doubled.
5.Cows munch mostly grasses and hay—yet they grow big and hefty.Why？ Because of the rumen.The rumen holds 160 liters of food and billions of microbes.These microscopic bacteria and protozoa break down cellulose and fiber into digestible nutrients.A cow couldn't live without its microbes.As the microbes digest cellulose,they release methane.The process occurs in all animals with a rumen(cows,sheep,and goats,for example),and it makes them very gassy.It.s part of their normal digestion process.When they chew their cud,they regurgitate some food to rechew it,and all this gas comes out.the average cow expels 600 liters of methane a day.
6.That's why we say livestock gas is also a major factor of causing the global warming.
詞匯：
methane 甲烷 munch 用力咀嚼
odorless 無味的 hefty 健壯的
potent 強(qiáng)有力的 rumen 瘤胃
belch 打嗝 protozoa 原生動(dòng)物（復(fù)數(shù))
livestock 家畜，牲畜 cellulose 纖維素
landfill 埋填的廢渣 nutrient 有營養(yǎng)的
magnify 擴(kuò)大 cud 反芻的食物
guzzle 大量消耗（燃料等) regurgitate 反芻
注釋：
1.once released into the atmosphere…：一旦（甲烷)釋放到大氣中……once released into the atmosphere相當(dāng)于once methane is released into the atmosphere.
2.Molecule for molecule，molecule's heat-trapping power in the atmosphere is 21 times stronger than carbon dioxide…：按分子與分子對比，甲烷在大氣中吸熱的能力比二氧化碳強(qiáng)20倍……介詞for表示“對比或比例關(guān)系”。
3.without greenhouse gases…life as we know it could'n't exist：沒有溫室氣體……我們所知道的生命就不能生存。本句中，life是主語。as從句中的it指代life.
4.Atmospheric concentrations of methane：甲烷在大氣中的濃度。
練習(xí)：
1.Paragraph 1 _____
2.Paragraph 2 _____
3.Paragraph 4 _____
4.Paragraph 5 _____
A.Life of Microscopic Bacteria in Livestock's Rumen
B.Ways to Reduce Methane's Heat-trapping Power
C.Agriculture Also Contributes to Increased Concentrations of Methane in the Atmosphere
D.Why Livestock Releases Methane
E.Methane as a Strong Greenhouse Gas
F.Livestock as a Prime Factor of the Greenhouse Effect
5.Methane is ___________ to the intensifying greenhouse effect.
6.Greenhouse gases are indispensable to mankind,but the problem mankind is faced with is ___________.
7.Generally people heap criticism on __________ for the planet's temperature rise.
8.Nothing has been mentioned in the passage about __________.
A.one of the major contributors
B.the ever-increasing atmospheric concentrations of greenhouse gases
C.big and hefty cows
D.livestock's normal digestion process
E.how to cut down the cattle populations
F.big industries and gas-guzzling vehicles
答案與題解：
1.E本段的第三句點(diǎn)出了 methane's heat-trapping power in the atmosphere is 21 times stronger than carbon dioxide.
2.F本段要表達(dá)的中心意思是： livestock排出的甲烷也是溫室效應(yīng)的一個(gè)主要源頭。
3.C本段表達(dá)的重點(diǎn)是用 but轉(zhuǎn)折的段后兩句。
4.D本段從科學(xué)的角度分析反芻動(dòng)物為什么會釋放出甲烷。
5.A，選A的依據(jù)在第一段的第二句和昀后一句。
6.B，選B的依據(jù)在第三段的第二句、第三句和第四段的第一句。這三個(gè)句子先后介紹了下列觀點(diǎn)：沒有溫室氣體，生物不能生存；人類燃燒能源，加劇溫室效應(yīng)；大氣甲烷含量增加一倍。
7.F第四段第二句直接談到這個(gè)問題。人們常常將不斷加劇的溫室效應(yīng)歸罪于大工業(yè)和汽車，而 cattle釋放甲烷的因素被忽略了。
8.E，選項(xiàng)E是本文沒有提到的內(nèi)容，也就是說，其他五個(gè)選項(xiàng)的內(nèi)容文章部有涉及。
1.Methane is a colorless,odorless gas;it is also a potent greenhouse gas,and once released into the atmosphere,it absorbs heat radiating from Earth's surface.That.s why methane is a major contributor to the planet's increasing temperature rise—or global warming.Molecule for molecule,methane.s heat-trapping power in the atmosphere is 21 times stronger than carbon dioxide,the most abundant greenhouse gas.
2.With 13 billion cows belching almost constantly around the world(100 million in the U.S.alone),it's no surprise that methane released by livestock is one of the chief global sources of the gas.Other prime methane sources： petroleum,drilling,coal mining,solid-waste landfills and wetlands.
3.Greenhouse gases like methane and carbon dioxide make up only a small part of Earth's atmosphere,which is 78 percent nitrogen and nearly 21 percent oxygen.And without greenhouse gases to trap the sun.s heat and warm the planet,life was we know it couldn't exist.But in the last 200 years,human activity that requires burning oil,natural gas,and coal for energy has magnified the greenhouse effect.
4.Atmospheric concentrations of methane have more than doubled in the last two centuries.Blame for this often focuses on big industries and gas-guzzling vehicles.But agriculture plays a major role,too.In the past 40 years alone,the global cattle population has doubled.
5.Cows munch mostly grasses and hay—yet they grow big and hefty.Why？ Because of the rumen.The rumen holds 160 liters of food and billions of microbes.These microscopic bacteria and protozoa break down cellulose and fiber into digestible nutrients.A cow couldn't live without its microbes.As the microbes digest cellulose,they release methane.The process occurs in all animals with a rumen(cows,sheep,and goats,for example),and it makes them very gassy.It.s part of their normal digestion process.When they chew their cud,they regurgitate some food to rechew it,and all this gas comes out.the average cow expels 600 liters of methane a day.
6.That's why we say livestock gas is also a major factor of causing the global warming.
詞匯：
methane 甲烷 munch 用力咀嚼
odorless 無味的 hefty 健壯的
potent 強(qiáng)有力的 rumen 瘤胃
belch 打嗝 protozoa 原生動(dòng)物（復(fù)數(shù))
livestock 家畜，牲畜 cellulose 纖維素
landfill 埋填的廢渣 nutrient 有營養(yǎng)的
magnify 擴(kuò)大 cud 反芻的食物
guzzle 大量消耗（燃料等) regurgitate 反芻
注釋：
1.once released into the atmosphere…：一旦（甲烷)釋放到大氣中……once released into the atmosphere相當(dāng)于once methane is released into the atmosphere.
2.Molecule for molecule，molecule's heat-trapping power in the atmosphere is 21 times stronger than carbon dioxide…：按分子與分子對比，甲烷在大氣中吸熱的能力比二氧化碳強(qiáng)20倍……介詞for表示“對比或比例關(guān)系”。
3.without greenhouse gases…life as we know it could'n't exist：沒有溫室氣體……我們所知道的生命就不能生存。本句中，life是主語。as從句中的it指代life.
4.Atmospheric concentrations of methane：甲烷在大氣中的濃度。
練習(xí)：
1.Paragraph 1 _____
2.Paragraph 2 _____
3.Paragraph 4 _____
4.Paragraph 5 _____
A.Life of Microscopic Bacteria in Livestock's Rumen
B.Ways to Reduce Methane's Heat-trapping Power
C.Agriculture Also Contributes to Increased Concentrations of Methane in the Atmosphere
D.Why Livestock Releases Methane
E.Methane as a Strong Greenhouse Gas
F.Livestock as a Prime Factor of the Greenhouse Effect
5.Methane is ___________ to the intensifying greenhouse effect.
6.Greenhouse gases are indispensable to mankind,but the problem mankind is faced with is ___________.
7.Generally people heap criticism on __________ for the planet's temperature rise.
8.Nothing has been mentioned in the passage about __________.
A.one of the major contributors
B.the ever-increasing atmospheric concentrations of greenhouse gases
C.big and hefty cows
D.livestock's normal digestion process
E.how to cut down the cattle populations
F.big industries and gas-guzzling vehicles
答案與題解：
1.E本段的第三句點(diǎn)出了 methane's heat-trapping power in the atmosphere is 21 times stronger than carbon dioxide.
2.F本段要表達(dá)的中心意思是： livestock排出的甲烷也是溫室效應(yīng)的一個(gè)主要源頭。
3.C本段表達(dá)的重點(diǎn)是用 but轉(zhuǎn)折的段后兩句。
4.D本段從科學(xué)的角度分析反芻動(dòng)物為什么會釋放出甲烷。
5.A，選A的依據(jù)在第一段的第二句和昀后一句。
6.B，選B的依據(jù)在第三段的第二句、第三句和第四段的第一句。這三個(gè)句子先后介紹了下列觀點(diǎn)：沒有溫室氣體，生物不能生存；人類燃燒能源，加劇溫室效應(yīng)；大氣甲烷含量增加一倍。
7.F第四段第二句直接談到這個(gè)問題。人們常常將不斷加劇的溫室效應(yīng)歸罪于大工業(yè)和汽車，而 cattle釋放甲烷的因素被忽略了。
8.E，選項(xiàng)E是本文沒有提到的內(nèi)容，也就是說，其他五個(gè)選項(xiàng)的內(nèi)容文章部有涉及。