全国英语等级考试三级句型学习(10)

　　The Greenhouse effect and Global warm***g

　　The heart-trapp***g capacity of the atmosphere is popularly known as the “greenhouse effect”. Despite pub***c ***ntroversy surround***g global warm***g, the natural greenhouse effect has been long estab***sh*** as fact *** the scientif*** ***mmunity.
Inde***, carbon dioxide, and other gases, the earth’s natural c***mate would be about 33℃ ***oler than it is. Life would h**e evolv*** quite differently *** such a c***mate.

　　Most scientists be***eve that the rapid expansion of agr***u***ure and ***dustrial acti***ties over the last several hundr*** years h**e ge***rat*** signif***ant ***creases *** carbon dioxide and ***tha*** *** the atmosphere. However, experts disagree about whether such changers h**e c***s*** the ***crease of approximately 0.5℃ *** the earth’s surface temperature that has been docu***nt*** over the past century. Many scientists cite the fact that 1997 was the war***st year on re***rd, follow***g a decade *** wh***h 9 of the 11 hottest years of this century were rep***t***, as strong, but circumstantial, e***dence that human acti***ties h**e a***er*** the earth’s c***mate. Other experts, however, be***eve this temperature trend is a natural variation.

　　Also disput*** is whether project***w***ld population growth *** m***e than 10 bil***on people by the year 2100 will resu*** *** a doub***ng *** trip***ng of atmospher*** ***ncentrations of carbon dioxide. If such a buildup o***urs, as many scientists pr******t, global surface temperatures ***uld ***crease by anywhere from about o*** Celsius degree *** about 4 Celsius degrees dur***g the ***xt century. The higher half of range ***volves temperature changes outside of those experienc*** by human ci******zations s***ce the end of the last ***e age so*** 10,000 years a***. Dur***g the last ***e age, **erage global temperatures were o***y about 5 Celsius degrees ***oler than the present period.

　　A temperature ***crease of several degrees Celsius ***uld resu*** *** a sea level rise rang***g from about 10 cm *** about 1 m. A sea level rise of about 0.5 m would be not***eable primarily *** the most vul***rable, low-ly***g islands and ***astal areas. Larger sea level rises would resu*** *** extensive flood***g of lowland beaches, wetlands, and ***astal settle***nts. M***eover, a higher sea level base would ***creases the risk of catastroph*** s***rm surges *** ***astal areas, s***ce flood***g would ***kely extend island well beyond his***r*** levels.

　　War***r temperature ***uld also ***tensify droughts *** so*** regions, destabi***ze e***systems, and c***se the dec****** *** ext***ction of so*** species. S***ce carbon dioxide enhances pho***synthesis, so*** scientists h**e calculat*** that higher ***ncentrations *** the atmostphere would ***crease the producti***ty of crops and f***ests. But others h**e po***t out that carbon dioxide ***crease and a warm***g c***mate ***uld en***urage the spread of destructive pests, ***clud***g we***s and disease-carry***g ***sects.