第三講歷史環(huán)境變遷講義

第三講地球環(huán)境歷史變遷錢維宏北京大學(xué)第三講

地球環(huán)境歷史變遷錢維宏Monsoon&EnvironmentResearchGroup北京大學(xué)物理學(xué)院錢維宏Monsoon&EnvironmentResearchGroup物理學(xué)院北京大學(xué)一基本概念層次理論相似理論動力系統(tǒng)層次理論時間層次季節(jié)內(nèi)變化；年際變化；年代際變化；世紀變化，全球增暖，小冰期空間層次時間層次與空間層次的匹配不同空間尺度系統(tǒng)之間的關(guān)系相似理論銀河系太陽系地月系土星與土星光環(huán)臺風(fēng)地球的演化動力系統(tǒng)系統(tǒng)的特征氣候系統(tǒng)氣候動力系統(tǒng)模式系統(tǒng)動力系統(tǒng)的數(shù)學(xué)描述二．氣候要素

——溫度代表平流層，對流層，地面，海洋和冰川

各個方面溫度因子的長期變化珊瑚

RarotongaIsland(21.5°S,159.5°W)

鉆孔溫度其他一些代用資料樹木年輪冰芯黃土黃土與全球變化

黃土在這里是指構(gòu)成中國黃土高原的"風(fēng)塵堆積系"，主要由黃土與紅土和夾于其中的古土壤層組成。全球變化是指人類活動和地質(zhì)營力所引起的地球環(huán)境系統(tǒng)的變化。中國黃土高原的地質(zhì)研究說明，全球變化是地球環(huán)境系統(tǒng)演化的普遍規(guī)律。地球環(huán)境演化可以劃分為“人類世全球變化”和“前人類世全球變化”兩個階段。也可以稱為人類全球變化和地質(zhì)全球變化。地質(zhì)全球變化是人類全球變化的基礎(chǔ)和放大。人類全球變化是加速了的地質(zhì)全球變化。

中國黃土高原地質(zhì)研究還表明黃土作為一種大陸沉積，它與地球兩極的冰蓋和大洋沉積都是新近地球環(huán)境變化的檔案庫。它們保存著地球環(huán)境演化歷史和過程的許多信息。最近研究發(fā)現(xiàn)中國“風(fēng)塵堆積系”可能提供較極地冰芯和一般深海沉積時間更長、內(nèi)容更為完整的、2200萬年以來全球變化的記錄。它為認識全球變化提供了新的證據(jù)和觀點。

全球陸地平均表面氣溫,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.

全球和不同緯帶一百多年來的變化趨勢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．氣候要素

——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．冰雪圈的環(huán)境變化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)大陸雪蓋1966年以來的北半球年平均雪蓋面積有減少趨勢。但是下降是不均勻的，在下降趨勢上迭加有7～8a振蕩。前期下降明顯，1980s中以來約減少10%（平均25.3×106km2）。雪蓋面積的減少主要出現(xiàn)在春、夏兩季。這可能是氣溫上升的結(jié)果。雪蓋面積與積雪區(qū)氣溫的相關(guān)系數(shù)達到-0.60。重建的雪蓋序列表明最近10a春夏雪蓋可能是20世紀的最低值。但是北美冬季的雪蓋可能有增加的趨勢，前蘇聯(lián)雪蓋也有類似的變化。這可能反映由于氣候變暖北半球中緯度冬季降水增加。山岳冰川根據(jù)世界范圍冰川資料,20世紀之前只有緩慢的后退，20世紀初后退加速，到20世紀末不少冰川后退了1～3公里。近20～30年熱帶的冰川后退迅速。近20年熱帶雪線上升約100m，這大約相當溫度上升0.5℃。此外，挪威、新西蘭的一些冰川有前進趨勢，這可能是氣候變暖近海地區(qū)降水增加所致MonthlyAntarcticsea-iceextentanomalies,relativeto1973-1996.ObserveddecreaseofNHseaiceextentduringthepast25years.

ObservedandmodeledvariationsofannualaveragesofNHseaiceextent..海冰1973年以來衛(wèi)星觀測北極的海冰面積也有下降趨勢。同時有5～6年的振蕩。自1978年至今，北極海冰面積可能減少2.8%。重建的20世紀北半球海冰序列表明20世紀后半，夏季海冰面積減少趨勢明顯。冬、春的減少出現(xiàn)在1970s中后期以后，秋季變化不明顯。盡管南極也在變暖，但是，1979～1996年南極海冰面積變化不大，或者甚至略有增加，速率約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．中國與東亞氣候與環(huán)境變化

人吃人蝗水淹城門大水秋旱春夏無雨歷史文獻DecadallyaveragedDrought/floodIndex(a)andsummerrainfall(b)anomaliesforthemid-lowervalleyChangjiangRiver.Incurvea,theanomaliesarewithrespecttowholeperiodAD1000-1999.(Wangetal,2000)近1.2ka中國東部（a）、西部（b）及全國（c）年平均氣溫對20世紀的偏差（分辨率50a）,虛線為整個序列的平均值(王紹武等2000)北京石筍紋層厚度中國西北樹木年輪黃河－長江－華南干濕變化長江流域干濕變化漢城降水中國各區(qū)氣溫變化中國各區(qū)降水變化干旱指數(shù)東亞季風(fēng)環(huán)流的年代際變化十年區(qū)域干旱頻率分布十年區(qū)域洪澇頻率分布七．米蘭科維奇理論地球在圍繞太陽公轉(zhuǎn)時發(fā)生偏心率的變化，具有１００ka和４１０ka的平均周期；地球旋轉(zhuǎn)軸傾斜角度也具平均周期為４１ka的變化；地球軌道也表現(xiàn)著歲差旋回，平均周期為２１.７ka〔1〕。地球軌道參數(shù)這種周期性的變化被稱之為米蘭科維奇旋回或節(jié)律。地球軌道旋回(米蘭科維奇節(jié)律)研究進展

早在19世紀初就有學(xué)者提出地球軌道參數(shù)的變化可以在地史時期的沉積記錄中觀察到，并開始細致地分析宇宙機制導(dǎo)致地球氣候變化的可能性，認為冰期主要是由于地－月距離變化所造成的認識〔1〕。通過研究科羅拉多州奈厄布拉勒(Niobrara)白堊中的灰?guī)r－頁巖韻律，首次將沉積旋回和地球軌道參數(shù)變化聯(lián)系在一起，認為除了天體運動狀態(tài)變化的控制因素外陸地上沒有任何作用能夠?qū)е氯绱擞幸?guī)律的節(jié)律。同時，將該認識延伸為地球軌道參數(shù)變化導(dǎo)致的氣候變化控制沉積物中灰?guī)r－頁巖韻律形成，并且這種對氣候變化敏感的沉積節(jié)律可以利用為“年代計”〔2〕。20世紀初萬年間隔沉積旋回的研究得到了２１３６年的周期，它們屬兩分點的歲差旋回〔3〕。米蘭科維奇系統(tǒng)研究了地球軌道參數(shù)的變化規(guī)律，定量給出了軌道參數(shù)與日射量變化的對應(yīng)關(guān)系，認為地球軌道參數(shù)變化是控制地球氣候變化的重要機制，但主要強調(diào)了三個軌道旋回準周期，即２１ka的歲差、４１ka的軸斜率和１００ka的偏心率旋回〔4〕。地球軌道旋回(米蘭科維奇節(jié)律)研究進展同時，他提出了第四紀冰期－間冰期氣候波動成因的天文學(xué)假說，推動了第四紀氣候研究，也為前第四紀地層旋回性沉積記錄的研究提供了可借鑒的理論。應(yīng)用深海鉆孔沉積物中有孔蟲介殼和極地冰川中氧和碳同位素的變化可以估計不同地史時期表層海水溫度的變化以及測算年代間隔，這些研究也發(fā)現(xiàn)，深海沉積物中氧同位素的浮動與日照值變化密切相關(guān)。珊瑚礁及深海沉積物精確的測年及深海鉆孔和冰川中氧同位素研究也發(fā)現(xiàn)了它們與日照值變化的高度耦合關(guān)系，同時證實更新世海平面升降具有２萬年的歲差周期。大量研究擴展了長周期偏心率旋回的概念，認為可能還存在603、1294、2035和3416ka的周期。上述翔實的實際資料和數(shù)據(jù)以及70年代以來穩(wěn)定同位素分析和計算機數(shù)據(jù)處理水平的提高使米蘭科維奇理論得到了有力的