第三讲历史环境变迁讲义

第三讲地球环境历史变迁钱维宏北京大学第三讲

地球环境历史变迁钱维宏Monsoon&EnvironmentResearchGroup北京大学物理学院钱维宏Monsoon&EnvironmentResearchGroup物理学院北京大学一基本概念层次理论相似理论动力系统层次理论时间层次季节内变化；年际变化；年代际变化；世纪变化，全球增暖，小冰期空间层次时间层次与空间层次的匹配不同空间尺度系统之间的关系相似理论银河系太阳系地月系土星与土星光环台风地球的演化动力系统系统的特征气候系统气候动力系统模式系统动力系统的数学描述二．气候要素

——温度代表平流层，对流层，地面，海洋和冰川

各个方面温度因子的长期变化珊瑚

RarotongaIsland(21.5°S,159.5°W)

钻孔温度其他一些代用资料树木年轮冰芯黄土黄土与全球变化

黄土在这里是指构成中国黄土高原的"风尘堆积系"，主要由黄土与红土和夹于其中的古土壤层组成。全球变化是指人类活动和地质营力所引起的地球环境系统的变化。中国黄土高原的地质研究说明，全球变化是地球环境系统演化的普遍规律。地球环境演化可以划分为“人类世全球变化”和“前人类世全球变化”两个阶段。也可以称为人类全球变化和地质全球变化。地质全球变化是人类全球变化的基础和放大。人类全球变化是加速了的地质全球变化。

中国黄土高原地质研究还表明黄土作为一种大陆沉积，它与地球两极的冰盖和大洋沉积都是新近地球环境变化的档案库。它们保存着地球环境演化历史和过程的许多信息。最近研究发现中国“风尘堆积系”可能提供较极地冰芯和一般深海沉积时间更长、内容更为完整的、2200万年以来全球变化的记录。它为认识全球变化提供了新的证据和观点。

全球陆地平均表面气温,不同的作者(a)(Jonesetal.,2001)和(b)其他作者(a)Annualanomaliesofglobalaverageland-surfaceairtemperature(°C),1861to2000,relativeto1961to1990values.BarsandsolidcurvearefromCRU(Jonesetal.,2001).Valuesarethesimpleaverageoftheanomaliesforthetwohemispheres.Thesmoothedcurvewascreatedusinga21-pointbinomialfiltergivingneardecadalaverages.(b)As(a)butsmoothedcurvesonlyfromNCDC(updatedfromPetersonandVose,1997)–thinsolidcurve;GISS(adaptedfromHansenetal.,1999)–thickdashedcurve;SHI(updatedfromVinnikovetal.,1990)–thindashedcurveto1999only;PetersonandVose(1997)–thinsolidcurve.Thicksolidcurve–asin(a).TwostandarderroruncertaintiesarecentredontheCRUcurveandareestimatedusinganoptimumaveragingmethod(Follandetal.,2001)andincludeuncertaintiesduetourbanisationbutnotduetouncertaintiesinthermometerexposures.TheNCDCcurveistheweightedaverageofthetwohemispheresaccordingtotheareasampled,whichaccountsformostofthedifferencesfromtheCRUcurve.

Trendsinannualdiurnaltemperaturerange(DTR,°C/decade),from1950to1993,fornon-urbanstationsonly,updatedfromEasterlingetal.(1997).Decreasesareinblueandincreasesinred.

Cloudcover(solidline)andDTR(°C,dashedline)forEurope,USA,Canada,Australia,theformerSovietUnion,andeasternChina(fromDaietal.,1997a).NotethattheaxisforDTRhasbeeninverted.Therefore,apositivecorrelationofcloudcoverwithinvertedDTRindicatesanegativecloudcover/DTRcorrelation.

Testsofbiasadjustmentstoseasurfacetemperature(SST)usingaclimatemodel(Follandetal.,2001).Blackline-annualmeanobservedlandsurfaceairtemperature(SAT)anomaly(°C)froma1946to1965average(Jones,1994),aperiodbeforemajoranthropogenicwarming.Redline–annualaveragesoffoursimulationsofSATanomaliesusinguncorrectedSSTdata,1872to1941,andanaverageofsixsimulationsfor1941to1998.Blueline–averageofsixsimulationsofSAT,forcedwithSSTdatacorrectedupto1941.

全球和不同纬带一百多年来的变化趋势Smoothedannualanomaliesofglobalaverageseasurfacetemperature(°C)1861to2000,relativeto1961to1990(bluecurve),nightmarineairtemperature(greencurve),andland-surfaceairtemperature(redcurve).ThedataarefromUKMetOfficeandCRUanalyses(adaptedfromJonesetal.,2001,andParkeretal.,1995).Thesmoothedcurveswerecreatedusinga21-pointbinomialfiltergivingnear-decadalaverages.Alsoshown(inset)arethesmootheddifferencesbetweentheland-surfaceairandseasurfacetemperatureanomalies.

Smoothedannualanomaliesofcombinedland-surfaceairandseasurfacetemperatures(°C),1861to2000,relativeto1961to1990,for(a)NorthernHemisphere;(b)SouthernHemisphere;and(c)Globe.Thesmoothedcurveswerecreatedusinga21-pointbinomialfiltergivingnear-decadalaverages.Optimallyaveragedanomalies(Follandetal.,2001)–solidcurves;standardareaweightedanomalies(adaptedfromJonesetal.,2001)–dashedcurves.Alsoshownaretheunsmoothedoptimumaverages–redbars,andtwicetheirstandarderrors–widthdenotedbyblack“I”.NotethatoptimumaveragesfortheSouthernHemispherearealittlewarmerbefore1940,whenthedataaresparse,thanthearea-weightedaverages.However,thetwotypesofaveraginggivesimilarresultsintheNorthernHemisphere.

Smoothedannualanomaliesofglobalcombinedland-surfaceairandseasurfacetemperatures(°C),1861to2000,relativeto1961to1990,andtwicetheirstandarderrors.Thesmoothedcurvesandshadedareaswerecreatedusinga21-pointbinomialfiltergivingnear-decadalaverages,withappropriateerrors.Optimallyaveragedanomaliesanduncertainties(Follandetal.,2001)–solidcurveanddarkshading;standardareaweightedanomaliesanduncertainties(adaptedfromJonesetal.,1997b,2001)–dashedcurveandlightshading.Notethatuncertaintiesdecreaseafter1941duetothecessationofuncertaintiesduetobiascorrectionsinseasurfacetemperature.Ontheotherhand,uncertaintiesduetourbanisationofthelandcomponent,assessedaszeroin1900,continuetoincreaseafter1941toamaximumin2000.

Time-seriesfor1948to1998ofoceanheatcontentanomaliesintheupper300mforthetwohemispheresandtheglobalocean.Notethat1.5x1022Jequals1watt-year-m-2averagedovertheentiresurfaceoftheearth.Verticallinesthrougheachyearlyestimateare±onestandarderror(Levitusetal.,2000b).

(a)Seasonalanomaliesofglobalaveragetemperature(°C),1958to2000,relativeto1979to1990forthelowertroposphere,asobservedfromsatellites(MSU2LT)andballoons(UKMO2LT),andforthesurface(adaptedfromJonesetal.,2001).Alsoshown(bottomgraph)arethedifferencesbetweenthesurfacetemperatureanomaliesandtheaveragesofthesatelliteandballoon-basedobservationsofthelower-tropo-spherictemperatureanomalies.(b)As(a)butforthetemperatureofthelowerstratosphere,asobservedfromsatellites(MSU4andSSU15X)andballoons(UKMO4).ThetimesofthemajorexplosiveeruptionsoftheAgung,ElChichonandMt.Pinatubovolcanoesaremarked.Alsoshown(bottomgraph)arethedifferencesbetweentheMSU4andUKMO4basedtemperatureanomalies.

(a)AnomaliesofmonthlysnowcoverovertheNorthernHemispherelands(includingGreenland)betweenNovember1966andMay2000.

(b)Seasonalsnowcoveranomalies(inmillionkm2)versustemperatureanomalies(in°C).

MonthlyArcticsea-iceextentanomalies,1973to2000,relativeto1973to1996.

Time-seriesofannualandseasonalsea-iceextentintheNorthernHemisphere,1901to1998,

MonthlyAntarcticsea-iceextentanomalies,1973to2000,relativeto1973to1996.

Meanicethicknessatplaceswhereearlycruiseswere(nearly)collocatedwithcruisesinthe1990s.

Reconstructedglobalgroundtemperatureestimatefromboreholedataoverthepastfivecenturies,relativetopresentday.Shadedareasrepresent±twostandarderrorsaboutthemeanhistory(Pollacketal.,1998).

MillennialNorthernHemisphere(NH)temperaturereconstruction(blue)andinstrumentaldata(red)fromAD1000to1999,adaptedfromMannetal.(1999).SmootherversionofNHseries(black),lineartrendfromAD1000to1850(purple-dashed)andtwostandarderrorlimits(greyshaded)areshown.

Comparisonofwarm-season(Jonesetal.,1998)andannualmean(Mannetal.,1998,1999)multi-proxy-basedandwarmseasontree-ring-based(Briffa,2000)millennialNorthernHemispheretemperaturereconstructions.

Time-seriesillustratingtemperaturevariabilityoverthelastabout400ky(updatedfromRosteketal.,1993;Schneideretal.,1996;MacManusetal.,1999;Reilleetal.,2000).Theuppermosttime-seriesdescribesthepercentageoftreepollenthatexcludespollenfrompinetreespecies.Thehigherthispercentage,thewarmerwastheclimate.

RecordsofclimatevariabilityduringtheHoloceneandthelastclimatictransition,includingthe8.2kyBPevent

Variationsoftemperature,methane,andatmosphericcarbondioxideconcentrationsderivedfromairtrappedwithinicecoresfromAntarctica(adaptedfromSowersandBender,1995;Blunieretal.,1997;Fischeretal.,1999;Petitetal.,1999).

三．气候要素

——降水

Trendsinannualmeansurfacewatervapourpressure,1975to1995,expressedasapercentageofthe1975to1995mean.

Annuallyaveragedtrendsinsurfaceto500hPaprecipitablewaterat0000UTCfortheperiod1973to1995.

四．ExtremeEventsAnexample(fromGroismanetal.,1999)ofthesensitivityofthefrequencyofheavydailyrainfalltoashiftinthemeantotalrainfall,basedonstationdatafromGuangzhou,China.Thisexampleusesathresholdof50mmofprecipitationperday.Itshowstheeffectsofa10%increaseanda10%decreaseinmeantotalsummerrainfall,basedonagammadistributionoftherainfallwithaconstantshapeparameter

Lineartrends(%/decade)ofheavyprecipitation(abovethe90thpercentile)andtotalprecipitationduringtherainyseasonovervariousregionsoftheglobe.

Topfigure,decadalvariationsinhurricanesmakinglandfallintheUSA(updatedfromKarletal.,1995).Bottomfigure,interannualvariabilityinthenumberofmajorhurricanes(Saffir-Simpsoncategories3,4,and5)andthelong-termaverageacrosstheNorthAtlantic(fromLandseaetal.,1999).

Annualtotalnumberofverystrongthroughviolent(F3-F5)tornadoesreportedintheUSA,whicharedefinedashavingestimatedwindspeedsfromapproximately70to164ms-1.

五．冰雪圈的环境变化SnowCoverSnowCoverAboveFigure:(a)AnomaliesofmonthlysnowcoverovertheNorthernHemispherelands(includingGreenland)betweenNovember1966andMay2000.Alsoshownaretwelve-monthrunninganomaliesofhemisphericsnowextent,plottedontheseventhmonthofagiveninterval.AnomaliesarecalculatedfromNOAA/NESDISsnowmaps.Meanhemisphericsnowextentis25.2millionkm2forthefullperiodofrecord.thecurveofrunningmeansisextrapolatedbyusingperiodofrecordmonthlymeansfor12monthsinthelate1960sinordertocreateacontinuouscurveofrunningmeans.MissingmonthsfellbetweenMayandOctober,andnowintermonthsaremissing.June1999toMay2000valuesarebasedonpreliminaryanalyses.(b)Seasonalsnowcoveranomalies(inmillionkm2)versustemperatureanomalies(in°C).Bothsnowandtemperatureanomaliesareareaaveragesovertheregionforwhichclimatologicalvaluesofseasonalsnow-coverfrequency(basedonthe1973to1998period)arebetween10and90%.Seasonisindicatedatthetopofeachpanel.Axisforsnowanomalyontheleft-hand-sideyaxis,axisfortemperatureanomalyisontheright-hand-sideyaxis.Barplotindicatestime-seriesofsnowcoveranomalies.Continuouscolourcurveindicatesnine-pointweightedaverageofsnow-coveranomaly.Dashedblackcurveindicatestime-seriesofnine-pointweightedaverageofareaaveragetemperatureanomaly.Snow-covercalculationsarebasedontheNOAA/NESDISsnowcoverdatafortheperiod1973to1998(updatedfromRobinsonetal.,1993).TemperaturecalculationsarebasedontheJonesdataset,henceanomaliesarewithrespecttothetimeperiod1961to1990.Snowanomaliesarewithrespecttothetimeperiod1973to1998.Correlationcoefficient(r)betweenseasonalsnowcoveranomaliesandtemperatureanomaliesisindicatedinparentheses.(FigurecontributedbyDavidA.RobinsonandAnjuliBamzai,RutgersUniversity.)Sea-iceextentandthicknessSea-iceextentandthicknessAboveFigure:MonthlyArcticsea-iceextentanomalies,1973to2000,relativeto1973to1996.ThedataareablendofupdatedWalsh(Walsh,1978),GoddardSpaceFlightCentersatellitepassivemicrowave(ScanningMultichannelMicrowaveRadiometer(SMMR)andSpecialSensorMicrowave/Imager(SSM/I))deriveddata(Cavalierietal.,1997)andNationalCentersforEnvironmentalPredictionsatellitepassivemicrowavederiveddata(Grumbine,1996).UpdateddigitisedicedatafortheGreatLakesarealsoincluded(Assel,1983).Sea-iceextentandthicknessSea-iceextentandthicknessAboveFigure:Time-seriesofannualandseasonalsea-iceextentintheNorthernHemisphere,1901to1999,(AnnualvaluesfromVinnikovetal.,1999b;seasonalvaluesupdatedfromChapmanandWalsh,1993).Sea-iceextentandthicknessSea-iceextentandthicknessAboveFigure:MonthlyAntarcticsea-iceextentanomalies,1973to2000,relativeto1973to1996.ThedataareablendofNationalIceCenter(NIC)chart-deriveddata(Knight,1984),GoddardSpaceFlightCentersatellitepassive-microwave(ScanningMultichannelMicrowaveRadiometer(SMMR)andSpecialSensorMicrowave/Imager(SSM/I))deriveddata(Cavalierietal.,1997)andNationalCentersforEnvironmentalPredictionsatellitepassive-microwavederiveddata(Grumbine,1996).Itisuncertainastowhetherthedecreaseininterannualvariabilityofseaiceafterabout1988isrealoranobservingbias.Sea-iceextentandthicknessSea-iceextentandthicknessAboveFigure:Meanicethicknessatplaceswhereearlycruiseswere(nearly)collocatedwithcruisesinthe1990s.Earlydata(1958to1976)areshownbyopentriangles,andthosefromthe1990sbysolidsquares,bothseasonallyadjustedtoSeptember15.Thesmalldotsshowtheoriginaldatabeforetheseasonaladjustment.Thecrossingsaregroupedintosixregionsseparatedbythesolidlines.FromRothrocketal.(1999).MountainglaciersMountainglaciersAboveFigure:Acollectionoftwentyglacierlengthrecordsfromdifferentpartsoftheworld.Curveshavebeentranslatedalongtheverticalaxistomakethemfitinoneframe.Thegeographicaldistributionofthedataisalsoshown,thoughasingletrianglemayrepresentmorethanoneglacier.DataarefromtheWorldGlacierMonitoringService(http://www.geo.unizh.ch/wgms/)withsomeadditionsfromvariousunpublishedsources.AnomaliesofmonthlysnowcoverextentoverNorthernHemispherelands(includingGreenland)大陆雪盖1966年以来的北半球年平均雪盖面积有减少趋势。但是下降是不均匀的，在下降趋势上迭加有7～8a振荡。前期下降明显，1980s中以来约减少10%（平均25.3×106km2）。雪盖面积的减少主要出现在春、夏两季。这可能是气温上升的结果。雪盖面积与积雪区气温的相关系数达到-0.60。重建的雪盖序列表明最近10a春夏雪盖可能是20世纪的最低值。但是北美冬季的雪盖可能有增加的趋势，前苏联雪盖也有类似的变化。这可能反映由于气候变暖北半球中纬度冬季降水增加。山岳冰川根据世界范围冰川资料,20世纪之前只有缓慢的后退，20世纪初后退加速，到20世纪末不少冰川后退了1～3公里。近20～30年热带的冰川后退迅速。近20年热带雪线上升约100m，这大约相当温度上升0.5℃。此外，挪威、新西兰的一些冰川有前进趋势，这可能是气候变暖近海地区降水增加所致MonthlyAntarcticsea-iceextentanomalies,relativeto1973-1996.ObserveddecreaseofNHseaiceextentduringthepast25years.

ObservedandmodeledvariationsofannualaveragesofNHseaiceextent..海冰1973年以来卫星观测北极的海冰面积也有下降趋势。同时有5～6年的振荡。自1978年至今，北极海冰面积可能减少2.8%。重建的20世纪北半球海冰序列表明20世纪后半，夏季海冰面积减少趋势明显。冬、春的减少出现在1970s中后期以后，秋季变化不明显。尽管南极也在变暖，但是，1979～1996年南极海冰面积变化不大，或者甚至略有增加，速率约1.3%/10a.Tracksinbluearefrom1990'sscientificcruises.Tracksinredarefromearliermilitarymissions.

Despiteuncertainitesaboutlocationsandtiming,overallastunningresultemerged.Averagedover29widelyscatteredlocations,icethinnedmorethan40%inbarelythreedecades.Amountsofthinningdifferedindifferentregions,butanoverallthinningpatternwasclear.

AboveFigure:RecordsofclimatevariabilityduringtheHoloceneandthelastclimatictransition,includingthe8.2kyBPevent(adaptedfromJohnsenetal.,1992;Hughenetal.,1996;Thompsonetal.,1998;vonGrafensteinetal.,1999;Jouzeletal.,2001).Theshadedareasshowthe8.2kyBPevent,theYoungerDryaseventandtheAntarcticColdReversal.ThegreyscaleusedintheTropicalNorthAtlanticrecordisameasureofseasurfacetemperature,deducedfromthecolourofplanktonrichlayerswithinanoceansedimentcore.六．中国与东亚气候与环境变化

人吃人蝗水淹城门大水秋旱春夏无雨历史文献DecadallyaveragedDrought/floodIndex(a)andsummerrainfall(b)anomaliesforthemid-lowervalleyChangjiangRiver.Incurvea,theanomaliesarewithrespecttowholeperiodAD1000-1999.(Wangetal,2000)近1.2ka中国东部（a）、西部（b）及全国（c）年平均气温对20世纪的偏差（分辨率50a）,虚线为整个序列的平均值(王绍武等2000)北京石笋纹层厚度中国西北树木年轮黄河－长江－华南干湿变化长江流域干湿变化汉城降水中国各区气温变化中国各区降水变化干旱指数东亚季风环流的年代际变化十年区域干旱频率分布十年区域洪涝频率分布七．米兰科维奇理论地球在围绕太阳公转时发生偏心率的变化，具有１００ka和４１０ka的平均周期；地球旋转轴倾斜角度也具平均周期为４１ka的变化；地球轨道也表现着岁差旋回，平均周期为２１.７ka〔1〕。地球轨道参数这种周期性的变化被称之为米兰科维奇旋回或节律。地球轨道旋回(米兰科维奇节律)研究进展

早在19世纪初就有学者提出地球轨道参数的变化可以在地史时期的沉积记录中观察到，并开始细致地分析宇宙机制导致地球气候变化的可能性，认为冰期主要是由于地－月距离变化所造成的认识〔1〕。通过研究科罗拉多州奈厄布拉勒(Niobrara)白垩中的灰岩－页岩韵律，首次将沉积旋回和地球轨道参数变化联系在一起，认为除了天体运动状态变化的控制因素外陆地上没有任何作用能够导致如此有规律的节律。同时，将该认识延伸为地球轨道参数变化导致的气候变化控制沉积物中灰岩－页岩韵律形成，并且这种对气候变化敏感的沉积节律可以利用为“年代计”〔2〕。20世纪初万年间隔沉积旋回的研究得到了２１３６年的周期，它们属两分点的岁差旋回〔3〕。米兰科维奇系统研究了地球轨道参数的变化规律，定量给出了轨道参数与日射量变化的对应关系，认为地球轨道参数变化是控制地球气候变化的重要机制，但主要强调了三个轨道旋回准周期，即２１ka的岁差、４１ka的轴斜率和１００ka的偏心率旋回〔4〕。地球轨道旋回(米兰科维奇节律)研究进展同时，他提出了第四纪冰期－间冰期气候波动成因的天文学假说，推动了第四纪气候研究，也为前第四纪地层旋回性沉积记录的研究提供了可借鉴的理论。应用深海钻孔沉积物中有孔虫介壳和极地冰川中氧和碳同位素的变化可以估计不同地史时期表层海水温度的变化以及测算年代间隔，这些研究也发现，深海沉积物中氧同位素的浮动与日照值变化密切相关。珊瑚礁及深海沉积物精确的测年及深海钻孔和冰川中氧同位素研究也发现了它们与日照值变化的高度耦合关系，同时证实更新世海平面升降具有２万年的岁差周期。大量研究扩展了长周期偏心率旋回的概念，认为可能还存在603、1294、2035和3416ka的周期。上述翔实的实际资料和数据以及70年代以来稳定同位素分析和计算机数据处理水平的提高使米兰科维奇理论得到了有力的