TPO-10 Reading 2 阅读译文

Variations in the Climate气候变化One of the mostdifficult aspectsof decidingwhether currentclimatic eventsrevealevidence of the impactof human activities is that itis hardto geta measureof whatconstitutesthe naturalvariability of the climate.We knowthat overthe pastmillennia theclimatehas undergonemajor changeswithout anysignificant humanintervention.We alsoknowthat the global climatesystem isimmensely complicatedand thateverything isinsome wayconnected,and sothe systemis capableof fluctuatingin unexpectedways.Weneed thereforeto knowhow muchthe climatecan varyof itsown accordin ordertointerpret withconfidence theextent towhich recentchanges arenatural asopposed tobeingthe resultof humanactivities.确定现在的气候事件是否证明人类活动影响的最大困难之一在于很难找到一种方法来确定是什么构成了气候的自然可变性我们知道在过去的几千年里，气候在没有重大人类干预下也经历了主要变化我们还知道全球气候系统是非常复杂的，所有因素都在某些方面互相联系，因此这个系统以意想不到的方法变化着因此，我们需要知道气候在多大程度上是自然变化的，以便于确切解释出最近的变化在多大程度上是自然的，或相反是人类活动的结果Instrumental recordsdo notgo backfar enoughto provideus withreliable measurementsofglobal climaticvariability ontimescales longerthan acentury.What wedo knowisthataswe includelonger timeintervals,the recordshows increasingevidence ofslow swingsinclimate betweendifferent regimes.To buildup abetter pictureof fluctuationsappreciablyfurther backin timerequires usto useproxy records.仪器记录不能追溯回那么久远以提供给我们长于一个世纪的时间标准下的全球气候可变性的可信测量方法我们所确知的就是当我们想包括更长久的时间跨度,记录揭示了在不同制度中缓慢的摇摆的更多的证据为了建立一个略久远变化的更好的变化描述，需要我们使用替代记录Over longperiods oftime,substances whosephysical andchemical propertieschange withtheambient climateat thetime can be depositedin asystematic wayto provideacontinuous recordof changes in thoseproperties overtime,sometimes forhundreds orthousandsof years.Generally,the layeringoccurs onan annualbasis,hence theobservedchanges in the records can bedated.Information ontemperature,rainfall,and otheraspectsof the climate thatcanbeinferred from the systematicchanges inproperties isusuallyreferred toas proxydata.Proxy temperaturerecords have been reconstructedfrom icecoredrilled outof thecentral Greenland ice cap,calcite shellsembedded inlayered lakesedimentsin WesternEurope,ocean floorsediment cores from thetropical AtlanticOcean,ice coresfrom Peruvianglaciers,andicecoresfromeastern Antarctica.While theserecordsprovide broadlyconsistent indicationsthat temperaturevariations canoccur ona globalscale,there arenonetheless someintriguing differences,which suggestthat thepattern oftemperaturevariations inregional climatescan alsodiffer significantlyfrom eachother.经过很长一段时间，物理和化学特征随着当时周围的气候变化的物质将会以系统的方法沉淀，这可以提供那些特征在超长时间里变化的连续记录，这个超长时间有时可达几百年或几千年通常，分层堆积是每年发生的，因此在记录中可观察的变化可以用来确定日期关于温度，降雨和气候的其他方面的信息通常都是指替代数据，这些信息可以从这种特征的系统变化中推断出来替代温度记录已被重建通过钻取自格陵兰冰帽中部的冰核，西欧深嵌在分层湖底沉积物中的方解石壳，取自热带大西洋的海底沉积物核，取自秘鲁冰河的冰核，和取自东南极洲的冰核尽管这新记录提供了广范一致的迹象指出温度变化可在全球范围内发生，但仍存在引人发问的差异，这些差异表示区域性气候的温度变化方式可以如此不同What theproxy recordsmake abundantlyclear isthat therehavebeensignificant naturalchangesintheclimate overtimescales longerthan afew thousandyears.Equally striking,however,is therelative stabilityof theclimate inthe past10,000years theHoloceneperiod.代理记录所充分解释的是在长于几千年的时间跨度里存在着显著的自然气候变化但同样令人惊讶的是在过去的一万年全新世中气候的相对稳定【*全新世在地质年表上第四纪后两世从更新世结束一直到现在岩石时期的泥沙时期一译者】To theextent thatthe coverageof theglobal climatefrom theserecordscanprovide ameasureof itstrue variability,it shouldat leastindicate how all thenatural causesofclimate changehave combined.These includethe chaoticfluctuations ofthe atmosphere,the slowerbut equallyerratic behavioroftheoceans,changesinthe landsurfaces,and theextentof iceand snow.Also includedwill beany variationsthat havearisen fromvolcanicactivity,solar activity,and,possibly,humanactivities.这些记录中对全球气候的覆盖度已经达到了可以提供气候可变性的方法的程度，它应该至少揭示所有引起气候变化的自然原因是怎样结合的这些原因包括混乱的大气波动，相对较慢但相当混乱的海洋活动，地表变化和冰雪的覆盖度还包括任何火山活动、太阳活动将会引起的变化或许也包括人类活动引起的变化One wayto estimatehowallthe variousprocesses leadingto climatevariability willcombineis byusing computermodels oftheglobal climate.They cando onlyso muchtorepresent thefull complexityoftheglobal climateand hencemay giveonly limitedinformationabout naturalvariability.Studies suggestthat todate thevariability incomputersimulations isconsiderably smallerthan indata obtainedfromtheproxy records.一种可估计所有这些导致气候变化的不同过程是如何结合的方法就是使用计算机全球气候模型它们可以做的只有这么多来描绘全球气候的全部复杂性，因此只能提供自然变化的有限信息研究表明迄今为止计算机模拟的可变性比取自代理记录的数据少得多In additionto theinternal variabilityoftheglobalclimatesystem itself,there isthe addedfactorof externalinfluences,such asvolcanoes andsolar activity.There isa growingbodyof opinionthat boththese physicalvariations havea measurableimpact ontheclimate.Thus weneed tobe ableto includethese inour deliberations.Some currentanalysesconclude thatvolcanoes andsolar activityexplain quitea considerableamount oftheobserved variabilityintheperiod fromthe seventeenthto theearly twentiethcenturys,butthat theycannot beinvoked toexplain therapid warmingin recentdecades.除全球气候系统本身的内部变化之外，还存在其他外部影响的因素，如火山或太阳活动有越来越多的观点认为这两种物理变化对气候有着可测量的影响因此我们需要能够考虑到这些一些现在的分析断定火山和太阳活动解释了自世纪到1720世纪早期的相当多的可观察到的变化但他们不能用以揭示最近几十年的迅速变暖。