专业英语温室效应优秀PPT.ppt

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1、Unit Four:The Greenhouse Effect第四课第四课 温室效应温室效应 New words:Triple 三倍于 quadruple 四倍于National Academy of Science 国家科学院Impact 影响 effect Feedback 反馈 annual 每年的Seasonal 每季的 Expand 扩展 extend spread Antarctic 南极洲 Greenland 格陵兰Flood 洪水泛滥 Bangladesh 孟加拉Bay of Bengal 孟加拉湾(BOB)Timely 定时的，刚好的 Zone 区域 region Infra

2、red radiation 红外辐射Climatic feedback 气候反馈Snow cover 雪盖 Et al.等等（人）etc.等等（物）4567 辐射辐射辐射辐射物体以物体以物体以物体以电电电电磁波或粒子流形式向四周磁波或粒子流形式向四周磁波或粒子流形式向四周磁波或粒子流形式向四周传递传递传递传递或交或交或交或交换换换换能量的方式。能量的方式。能量的方式。能量的方式。电电电电磁波磁波磁波磁波谱谱谱谱辐射的基本学问辐射的基本学问辐辐射是太阳能射是太阳能传输传输到地球的唯一途径到地球的唯一途径大气窗大气窗:713大气中的辐射传输过程大气中的辐射传输过程大气对短波的影响大气对短波的影响吸

3、取吸取散射散射反射反射吸取吸取逆辐射逆辐射大气对长波的影响大气对长波的影响 ppm:part per million P1:Man is reversing millions of years of natural evolution by putting into the atmosphere carbon that had been sequestered over the ages as fossil fuels.Atmospheric concentrations of CO2 are likely to double,and possibly triple,by 2100.Becau

4、se no historical precedent exists,reasonable expectations about future climate must be based on scientific evidence,not geological records.After evaluating the available evidence,the National Academy of Sciences concluded that a doubling of atmospheric concentrations of CO2 would warm the earths ave

5、rage temperature 1.5-4.5.P2:The greenhouse effect of the atmosphere has never been doubted.More of the suns radiation is visible light,which passes through the atmosphere largely undeterred.When the radiation strikes the earth,it warms the surface,which then radiates the heat as infrared radiation.H

6、owever,atmospheric CO2,water vapor,and some other gases absorb the infrared radiation rather than allow it to pass undeterredly through the atmosphere to space.Because the atmosphere traps the heat and warms the earth in a manner somewhat analogous to the glass panels of a greenhouse,this phenomenon

7、 is generally known as the“greenhouse effect”.Without this effect,the earth would be 33(60)colder that it is currently.P3:The extent to which CO2 absorbs heat has been known for almost a century,Scientists show that doubling of atmospheric CO2 would raise the average temperature1.2 if nothing else i

8、n the earths climatic system changed.However,many parts of the climate will change,amplifying the direct impact of CO2.Because these changes are not completely understood,the total warming is difficult to estimate.The current uncertainty surrounding the impact of CO2 on average temperature is center

9、ed around these climatic“feedback”,not the direct warming from CO2.P4：The most important feedback will result from the warmer atmospheres ability to retain moisture.Because water vapor also absorbs infrared radiation,additional heating will result.Hanson er al.estimate that double CO2 would increase

10、 the atmospheres water vapor content 30%,heating the earth and additional 1.4.P5:Another important positive feedback concerns the impact of snow and ice cover on the earths albedo,the extent to which it reflects sunlight.Ice and snow reflect most of the suns radiation,while water and soil absorb it.

11、An increase in surface temperatures would melt snow on land and floating ice and thereby allow the earth to absorb energy that would otherwise be reflected back into space.Hanson et al.estimate an additional warming of 0.4 from the albedo effect.P6:A feedback that is less understood is the impact of

12、 a global warming on clouds,which also reflect sunlight into space.The effects of clouds on the earths albedo depend on their heights and other properties,as well as the extent of cloud cover.Thus,the impact of a global warming on clouds is somewhat uncertain.Nevertheless,with somewhat less confiden

13、ce,Hanson et al.estimate a 2%reduction in cloud cover and a resulting warming of 0.5.They also estimate that increase in cloud height would result in an additional warming of 0.5,for a total impact of 1.0 from clouds.P7：Although the increase in the average temperature of the earth is a convenient sh

14、orthand description of CO2 induced climate change,it masks important regional implications.Most searchers agree that polar temperature would increase two to three times the earths average increase.The worlds climate depends largely on circulation patterns by which the atmosphere and the oceans trans

15、port heat from warm to cold regions.P7：As a result,any significant change in the difference between equatorial and polar temperatures could dramatically affect climatic patterns.A particularly important effect of these changes will be shifts in annual and seasonal precipitation and evaporation,with

16、some areas gaining and other losing.Furthermore,because hurricanes require an ocean temperature of 27 or warmer,a global warming could allow hurricanes to form at higher latitudes and during a greater part of the year.These changes could be important to coastal communities.P8：A more immediate(干脆的）co

17、ncern is that the projected global warming could raise the sea as much as one meter in the next century by heating ocean water,which would then expand,and by causing mountain glaciers and parts of ice sheets in West Antarctica,East Antarctica,and Greenland to melt or slide into the oceans.Thus,the s

18、ea could reach heights unprecedented in the history of civilization until this effort.No one had attempted to forecast sea level rise in specific years or determine its importance to todays activities.P9:If this prediction comes true,the water will flood over 15 percent if Bangladeshs territory,abou

19、t 12 to 15 percent of Egypts cultivated land and significantly reduce the territory of many island countries.In the United States,thousands of square miles of land could be lost,particularly in low-lying areas such as the Mississippi Delta,where the land is also subsiding at approximately one meter

20、per century.Storm damage,already estimated at over three billion dollars per year nationwide,could also increase the salinity of marshes,estuaries,and aquifers,disrupting marine life and possibly threatening some drinking water supplies.The greenhouse gases are also damaging the ozone layer surround

21、ing the earth which protects human beings from ultraviolet radiation.Research shows that cancer could increase by 3 percent for every 1 percent reduction in the ozone layer.Fortunately,the most adverse(不利的）effects can be avoided if timely actions are taken.P10：Although the climatic changes that coul

22、d result from CO2 emissions is poorly understood,there is complete agreement that CO2 concentrations are increasing.P11：Approximately one-half the CO2 released by combustion of fossil fuels has remained in the atmosphere.It is generally believed that most of the remaining CO2 has dissolved into the

23、oceans.Although tropical deforestation and cement production also result in CO2 emission,their contribution have been and will continue to be much less important.P12：Controlling the greenhouse gases,especially the increasing discharge（排放）of carbon dioxide has already become a key problem.The global

24、community must make efforts to reduce the greenhouse effect.P13：In the next few decades,however,CO2 emissions are unlikely to be curtailed,either voluntarily or by regulation.The worlds infrastructure is built around fossil fuels.The cost（成本）of using coal,gas and oil is low compared with nuclear and

25、 solar power,and this relative cost advantage（优势）is expected to continue.Therefore,a voluntary reduction in CO2 emissions is unlikely.P14：The only government action that could successfully reduce CO2 emissions would be to curtail the use of fossil fuels.Emission controls for CO2 from power plants（电厂

26、）would at least quadruple the cost of electricity.For smaller users of fossil fuels,such as homes and motor vehicles,control is not even feasible.Other plans,such as sequestering carbon in massive tree plantings,are even less plausible.P15：Even if political leaders decide to take drastic（严厉的）actions

27、 to limit worldwide consumption of fossil fuels,it is probably already too late to prevent significant rises in global temperatures and sea level.A recent study investigated the impact of drastic energy policy changes on the expected timing of a greenhouse warming(Seidel and Keyes,1983).The authors

28、concluded that such policies could have important impact by 2100,but would not substantially delay the 2 C warming expected by 2040.They estimated that a 300 percent tax on fossil fuels would delay the 2 C warming by only five years,and that even a worldwide ban on coal,shale（页 岩）oil,and synthetic f

29、uels would delay the warming by only twenty-five years,if implemented by 2000.Furthermore,such a ban would delay the rise in sea level expected through 2040 by only twelve years.P16：The political feasibility of instituting（制定）such a ban by 2000 is also doubtful,because only a worldwide agreement to

30、curtail emission could be successful.Any individual nation that curtails its own emissions will delay the day when CO2 concentrations double by a few years at most.Furthermore,because energy costs would increase for any nation that curtails its emissions,that nations industries would be placed at a

31、competitive disadvantage compared with those of the rest of the world.Finally,political leaders would require proof that such a policy would be more beneficial than adapting to higher CO2 levels.Such proof will probably remain impossible to provide for the foreseeable future.P17：The impact of increa

32、sing concentrations of greenhouse gases will almost certainly be an unprecedented global warming.Some people have suggested that this warming may be offset because the earth would otherwise（另外的方式）be entering a cool period.However,a natural cooling would take place over tens of thousands of years and

33、 is thus unlikely to significantly offset the global warming in the next century.Even a drastic increase in volcanic activity would offset less than 10 percent of the projected rise in sea level.P18：To meet the challenge of a global warming,society will need accurate information concerning the likel

34、y effects of sea level rise.Unfortunately,communities,corporations,and individuals do not by themselves have sufficient resources or incentives（激 励）to undertake the basic scientific research required to reduce existing uncertainties.This responsibility falls upon national governments throughout the world.Only their efforts can provide the information that decision makers will need.