2013年6月30日 星期日

DDS019-「災變氣候」與「中國歷史」(V)

〔承前文DDS018-「災變氣候」與「中國歷史」(IV)〕

在前面四篇短文中,我把中國歷史上,所有「史實記載有據」的社稷紛擾(即民變和外族入侵)及王朝興替,摘其精要,做了一個簡要的回顧,而這些事件的發生,又和當時氣候惡化下,所引發的災變(如長期大旱和飢荒)岌岌相關。從這個角度來看,中國歷史可以歸納出以下三個特點:

第一、自周室東遷(西元前 770年,周平王遷都洛邑)以來,歷代王朝的興替,都是發生在中國氣候急劇惡化的時候,而且每一個王朝,都是直接間接亡於所謂的「農民起義」或「外族入侵」〔例如,西漢末年的綠林、赤眉軍,東漢末年的黃巾軍,唐朝末年的黃巢軍,北宋末年的金(女真族) ,南宋末年的元(蒙古族) ,元朝末年的紅巾軍,明朝末年的李自成農民軍,和後來的滿清〕;

第二、中國歷史上最混亂的時代以及所有短命的王朝(春秋、戰國時代、三國、魏、西晉、東晉、南北朝、隋、五代十國及元朝),都是建立在氣候條件最為嚴峻的時代;

第三、中國歷代王朝建立的次序,都是先「西」後「東」(例如,先是「西周」再是「東周」、先是「西漢」再是「東漢」、先是「西晉」再是「東晉」)或是先「北」後「南」(例如,先是「北宋」再是「南宋」),這種由「西、北」向「東、南」的王朝更迭, 也都是因為中國特有的自然地理條件和氣候型態使然。

為了進一步闡明「災變氣候」和「中國歷史」間的這種因果關係,我以下圖(即前文提到的「概念模型(conceptual model)」)做一總結。如前文所述,中國這種歷史發展的「宿命」,主要是肇因於中國「自然地理(physiography)」上的特有「格局」。中國的氣候和地形,大略可依一「東北-西南」走向,劃分為西北、東南兩大區塊,西北地區,地勢高,多山多丘陵,氣候寒旱,而東南地區則地勢低緩,多平原、湖泊,氣候暖濕。這種不同的氣候型態,使得我們先民,依其生活方式逕分為遊牧(西北地區)和農耕(東南地區)兩大民族。這種截然不同的氣候型態,直接造成了這兩大民族,在文化、性格上的巨大差異,間接也影響了整個中國的文化內涵和歷史進展。俗話說「環境決定個性,個性決定命運」,對個人如此,對兩千多年來,中國歷史上的各個王朝,更是如此。


在所謂「氣候正常」下的平常年間,這兩個民族,尚能和睦相向,各自謀活,甚至通好結盟。但遇上天災荒年時,西北地區,糧草嚴重不足,人饑馬荒,遊牧民族本性又饒勇善戰,每每越境掠奪財物生畜,甚而攻城掠地,若遇官民抵抗,則是殺人縱火,兵戎相向。例如,明萬曆四十六年(西元 1618年),「奴爾哈赤」領兵進犯「大明」,主要就是因為遼東女真地區,發生嚴重災荒,兵民糧草不足,無法維生。〔註一:其實,當年「奴爾哈赤」並無滅「明」之心,他曾再三告誡子孫:「我們女真部族人口只有 300 萬,而「大明」人口總數已逾 1 1 千萬!」他曾提出,願以長江為界,與「大明」南、北分治;註二:「明」祟禎皇帝在得知此訊息後,也曾召開庭議,奈因重臣意見分岐,再加上先錯殺名將「袁祟煥」,後又有「吳三桂」的引清兵入關(山海關),再加上「李自成」農民軍的進逼,所謂「前有狼、後有虎」,「大明」國勢危於旦夕,於西元 1,644 年(歲次甲申)亡; 註三:祟禎皇帝,和歷代先皇相比,算是一個勤政愛民的好皇帝,他不近聲色,常常憂心國政,徹夜不眠,歷史上也給他相當正面的評價。他最終在「煤山(今北京景山)」壽皇亭自縊身亡,死時「自去冠冕,以髪披面」,自況「生時無用,死時可悲,愧對列祖列宗,不敢終於正寢」,並留遺言給「李自成」:「朕與你留宮殿、你與朕留太廟,朕與你留倉庫、你與朕留百姓」,讀者可以想像,祟禎皇帝此時內心的悲憤和無奈,即使一個好皇帝,最終還是「天命難違」,落得一個「亡國之君」的歷史駡名,誠所謂「天不殊心」;註四:下面的照片,是筆者當年,在北京地質大學蘇新教授盛邀和安排下,考察「李自成」入京時的故址史磧時,在景山當年祟禎皇帝自縊處,憑悼時所攝,照片中聳立的樹,已不是原來的樹,而是後來在原址,以同樣樹種重新種植的。〕


由於遊牧民族的頻頻入侵,華夏農耕民族被迫,不得不向東南撤遷,另立王室(例如,周室東遷和北宋南遷),嚴重時甚或淪於外族(例如,元、清兩朝之入主中原)。而在東南農耕地區,若逢連年災荒,農作歉收,百姓生活頓失依靠,加以官府無能,濟助無方,民怨長久累積下來,一觸即發。這時,若有人藉端鬧事,甚或舉著反朝廷的名號,掲竿而起,百姓一想,不反肯定是餓死,反了說不定還能殺出一條活路,自然馬上風起雲湧而來,這就是為什麼「農民軍」極盛時,動輒號稱有數十萬、百萬之眾,這時的朝廷,若還是祭不出有效辦法加以解決,那就只有等著覆亡。此外,中國歷史上常言:「大兵之後必有大災」,指的就是由於戰爭,造成更多的農田廢置,作物更是難以收成,造成更大的飢荒,餓殍遍野,甚至引發瘟疫,如此惡性循環,不知胡底,造成人口的極遽銳減,學者研究即曾指出,「元朝」時期(西元 13 14 世紀)和「明朝」末年,(西元 1,620 1,650 年)中國的總人口數,分別銳減 50%5,500 萬)和 43%7,000 萬)。

等到這一段「天災人禍」的大亂過後,舊的王朝被推翻而新的王朝也建立了。此時,氣候逐漸回復正常,而新王朝也能記取前朝教訓,勵精圖治,與民休養,社會秩序因而慢慢恢復,百姓又開始安居樂業,人口也隨著增加,天下也再度呈現出,一片欣欣向榮的景象,直到下次氣候又開始急劇惡化時為止。整個中國兩千多年來王朝的興替,就在這萬般無奈的輪迴中渡過,周而復始,屢試不爽。因此,氣候引起的災變,不但是歷代王朝揮之不去的夢魘,更是決定歷代王朝興衰、起滅的主要因素。

我們活在現今科技昌明的時代,當然和先民的農耕社會型態截然不同,尤其在面對「災變氣候」時的應變能力,更是大大增强了,但是「極端氣候」造成人類社會生命財物的破壞,還是時有所聞,如近日發生在印度、加拿大和歐洲的洪災,已令上萬人喪生,百萬人無家可歸。事實上,「聯合國環境委員會(United Nations Environment ProgrammeUNEP)」早就預警,到西元 2,050 年,全球所謂的「氣候難民(climate refugees)」,預估將高達 1 5,000 萬人。在其「地球危機(planet in peril)」報告中,有關「氣候」的危機,即佔全部 14 個危機中的 6 個。經濟學家更指出,往後這個世代的經濟,已進入一「全球變遷經濟(global change economy)」的時代,任何經濟規劃和發展(包括個人、群體、國家),都必需將「氣候」這個因素考慮進去。

         另外,我們也活在一個號稱文明的「地球村」世代,教育和專業素養,讓我們每個人(或國家),在溫飽條件下,自然是「理性」掛帥,但當環境(例如「氣候」)的壓迫,超過了我們的忍受度,底層的「人性」就開始顯露,個人(或集體的國家)為了「存活(survival)」,「資源(resources)」的獲得和擁有,就變成唯一的真理。在國與國間,這種生存的需求,必然造成地緣政治(geopolitics)上的緊張,甚至引發軍事上的對立和衝突〔註:說穿了,近來周邊國家,對我國東海、南海的覬覦和挑釁,即是典型的例子〕,這種情勢若持續發展下去,其下場為何,毋須我多贅言,聰明的讀者自應瞭然於心。歷史的可貴,在於後人可以「以史為鑑」,歷史的無情,卻往往是在人們的記憶快要忘卻時,又重複地發生。人類的歷史,就是這麼折騰,放眼現今世界,不論大國或小邦,對政治人物來說,要是不能有這種歷史的視野,整天還在「小鼻子、小眼睛」(這是台灣那些不入流的政客和名嘴,最常慣見的醜態,年青的讀者朋友,若你還認我是你老師的話,就千萬別學!)「內鬭內行、外鬬外行」,那就是百姓你我的悲哀,至於讀者的你,從我這連續五篇的短文中,又能得到多少啓發呢?(全文完)

2013年6月23日 星期日

DDS018-「災變氣候」與「中國歷史」(IV)

〔繼前文 DDS017-「災變氣候」與「中國歷史」(III)〕


為了便於讀者閱讀,我將前文末之「溫度異常曲線」再置於文首。要注意的是,我在該圖上方橫軸,也標記出自西漢末年以來,歷史上清楚記載的,所有平民起義(或稱農民革命)的名稱及其起迄時間。細心的讀者,立即可以發現,這些「起義」或「革命」幾乎都是發生在,氣候急遽惡化〔見圖中黃色粗線,由正值(暖)急速變成負值(冷)〕的時期,而且它們發生的時間,也大概就是宣告該王朝氣數已盡,到了該「改朝換代」的時候了,例如,「西漢(西元前 202 至西元 25 年)」末年時的「綠林赤眉(西元 21 至西元 25 年)」義軍;「東漢(西元 25 至西元 220 年)」末年時的「黃巾之亂(西元 184 至西元 204 年)」;「唐朝(西元 617 至西元 907 年)」末年時的「黃巢之亂(西元 867 至西元 884 年)」;「元朝(西元 1,279 至西元 1,367 年)」末年時的「紅巾之亂(西元 1,351 至西元 1,367 年)」和「明朝(西元 1,367 至西元 1,644 年)」末年時的「張獻忠、李自成農民軍(西元 1,630 至西元 1,644 年)」。

此外,由該「溫度異常曲線」也可看出,從西元 221 617 年間,全中國進入一低於平均溫,長達約 400 年之久的冷期,伴隨此冷期而來的惡化氣候條件(嚴寒和大旱),使得全中國在「兩漢」之後,又進入一兵戎相見、小國林立、割據分裂的局面,這段期間的王朝,基本上都是一些「短命」的王朝〔註:除「東晉」因短暫的回暖,國祚有百年之久外,其他王朝都是數十年就夭折〕,例如,「三國時期(西元 221 263 年)」、「魏朝(西元 263 280 年)」、「西晉(西元 280 316 年)」、「東晉(西元 316 417 年)」、「南北朝時期(西元 417 589 年)」及「隋朝(西元 589 617 年)」。同樣地,中國歷史上另一個極端混亂的時代(即「五代十國」;西元 907 960 年),和另一短命朝代「元朝(西元 12791367年)」,也都是因為氣候惡化的肆虐使致之的。

另外,「溫度異常曲線」所揭示的嚴寒時期(pronounced cold spells),包括「南北朝」、「唐朝」末年、「北宋」和「南宋」末年、「明代」中葉和末年、「清朝」初期,也和後來科學家們研究,石灰岩洞中的石筍(stalagmite),其所代表的氣候指標相合。其中尤以「明」、「清」時期的三個冷期,與發生在 15 18 世紀間的全球性「小冰期(Little Ice Age)」同步,因此,這些分別發生於西元 1,5001,650 1,850 年前後的劇冷期,古氣候學上分別稱之為「中國的第四、五、六次小冰期(Chinese Little Ice AgeCLIA)」(參見上圖)。也因為這種嚴寒又乾旱的氣候,使得「宋」、「元」、「明」、「清」四朝的整體國力,在歷史上的評價,也遠遠比不上所謂的「漢唐盛世」。但是,即使是盛世,還是逃脫不了,其末年時天候急速惡化,所帶來的惡運,誠所謂,氣候災變下「國恆亡」的歷史鐵律。

以上謹就中國「歷代王朝興衰」的歷史和「災變氣候」間的關連性,做了一個快速而簡要的描述,為了便於讀者進一步瞭解,這種氣候因素驅動下的歷史進展軌跡,我將以一「概念模型(conceptual model)」的方式來總結說明:「災變氣候」如何主導著中國歷史上各王朝的興亡交替。這個「模型」主要強調的是,這種發生在中國「歷史」和「氣候」間的糾纏(interweaving)和耦合(coupling),絶非「宿命」,更非「偶然」,它主要還是源自於,中國自古以來,特有的「人文社會型態」和「自然地理(physiography)條件」。

首先,我們都知道,中華文化,始自黃河流域,源遠流長,從黃帝紀元元年(西元前 2697 年)或夏王朝(中國第一個王朝,建於西元前 2070 年)算起,迄今已歷 4000 多年,是現今世上,唯一綿延不墜的文明故國。其次,中國國土幅員遼濶〔註:中國歷代王朝的疆域,雖因分裂或吞併,各有消長,但整體而言,自西漢以來,和目前中國領土相較,只大不小。以現今中國領土而言(見下衛星輿圖;資料來源:WikipediaFile: China 100.78713E 35.63718N),西起東經 74 度,東至東經 135 度,南起北緯 18 度,北至北緯 53 度,總面積約 960 萬平方公里,東西橫跨 5,200 公里,南北長達 5,500 公里〕,其中西北部,山脈連綿,峻嶺、高原、丘陵甚或沙漠交替(約佔總面積的三分之二),而其餘三分之一的東南部,則多為平原、湖泊、漥地。這種疆域遼邁,地形又高低起伏多變的特性,再加上季風(monsoon)交替,使得中國的氣候型態自是複雜多變,例如,若以「東北-西南」走向的 45o 角來區分(見下衛星輿圖),全中國的氣候型態,在西北地區大都以「乾、冷」為主,而東南地區則以「濕、暖」為主〔註:傳統上,中國的氣候帶以「秦嶺-淮河」一線為界,以北統稱北方,以南稱南方,西部則泛稱邊壃,南方暖濕,北方乾旱,冬季嚴寒。此「秦嶺-淮河」的軸線,和中國一月平均溫的 0 oC 等溫線及 800 釐米的等降雨線一致。〕,這種截然不同的氣候條件,也導致我們先民兩種不同的生活和居住形式:(1)世居於中國中部、黃河中游地區,以農耕為主的華夏(漢)民族以及(2)在西、北部,以狩、牧為生,「逐草而居」的游牧民族。


當氣候宜人時,整個中國沐浴在「物產豐饒」的情況下,不但在中原地區的華夏農耕百姓「豐衣足食」,地處西北塞外的游牧民族,也是「草長馬肥」,兩者間自是相安無事、融洽相向。但到了兇年,氣候惡化時,游牧民族,為了活命(包括人和牲畜),不得不越界掠奪,若遇頑抗,甚或刀刃相向,進而殺人刼奪糧草財物,造成華夏民族的巨大災難,這種兩大民族間的爭鬬,貫穿著整個中國歷史,其中尤以發生在西元 316 436 年,長達 120 年的「五胡亂華」〔註:「五胡」指的是匈奴、鮮卑、羯、羌、氐五族〕,最具代表性,其他還包括後來「北宋」時期的契丹和女真部族以及「明」末的滿州人。前文已提過,這種與中國歷代華夏王朝,如影隨形的「共業」,逼的各王朝不得不自西元前六世紀開始,歷經 2,200 多年,至十六世紀的「明」朝,築成長約 21,200 公里的「萬里長城」〔註:201265日,國家文物局宣布,歷經近5年的調查和認定,中國歷代長城總長度為21196.18公里,這是中國首次以科學方法,有系統地測量歷代長城的總長度。〕

          由於這種「西北」、「東南」氣候型態的強烈對比,當中國「氣候」開始全面惡化時,也是先由「西北」再向「東南」逐步漫延,此時的西北「游牧民族」自是首當其衝,進而和中原「農耕民族」間的對立、征伐也變的更加尖銳,套句現在的用語,那就是「力度、強度」加大了,這時中原的「華夏王朝」,也因氣候日趨惡化,早已是內亂民變不斷,「危如累卵」,那還經得起這些來自西北塞外「遊牧民族」的折騰(越界掠奪、殺伐),最後為了苟安自保,不得不先暫時退避東南,以求日後或能東山再起。這種謀國的權宜之計,直接反應在中國歷代「王朝交替」上的是:先「西」後「東」、先「北」後「南」,最終亡於「東、南」。歷史清楚記載:先有「西」周,後有「東」周,先有「西後有「先有「西」晉後有「東」晉,先有「北」宋後有「南」宋,最後覆亡的是「東」周、「東」晉、「南」宋。這種在氣候因素驅動下的中國歷史鐵律,即使在科技昌明的現今社會,還是足以發人深省的!(待續)

2013年6月16日 星期日

DDS017-「災變氣候」與「中國歷史」(III)

   註:我的好友,台大白書禎教授,針對我前文(DDS016)中,有關「蝗災」的敍述,提供了一些補充資料,謹摘錄於下,以餉讀者:

蘇軾在錢塘時見蝗災「上翳日月,下掩草木,遇其所落,彌望蕭然。」「飛蝗來時半天黑。」中國歷史上迭起蝗災,受災區多集中於河北、河南、山東三省,江蘇、安徽、湖北等省亦有分佈,嚴重時可能遍及整個黃土高原。鄧雲特《中國救荒史》統計,秦漢蝗災平均每 8.8 年一次,兩宋為 3.5 年,元代為 1.6 年,明、清兩代均為 2.8 年,受災範圍、受災程度堪稱世界之最。

白教授也提出了一個「大哉問」:「如果蝗災這般頻繁,如何能用來做為氣候變遷的 marker (指標)?」

敬覆如下:

1)「蝗災」是「氣候惡化(disastrous climate)」(特別是早期農耕社會)的指標,但並不足以用來做為「氣候變遷(climate change)」的指標。前文中的「蝗災」,指的是那些大規模成群飛離其原滋生地,越境侵襲作物的蝗蟲及其所造成的危害。因為只有這種數量大、範圍廣,甚至發生次數頻繁又集中的飛蝗肆虐,才足以造成大量作物的嚴重損失,使得賴以為生的務農百姓難以苟活。至於那些侷限於其滋生地、小規模、偶發性的,僅能歸之於一般所謂的蟲害(任何作物都有不同的蟲害),為了和「蝗災」區別,姑稱之為「蝗害」。這裡不得不佩服,中國文字的精妙,常言「災害」、「災害」,「災」在前,「害」在後,「災」大「害」小,尊卑有序,亂不了套的。

2)我未曾拜讀過鄧雲特先生著的《中國救荒史》,我不清楚作者使用的數據來源和統計方式,但相信這是一項辛苦又有價值的研究,我個人在此謹向鄧先生,致上最高敬意。但要注意的是其使用「年平均值」這個數字的意涵,以及使用它來研究或解讀「氣候議題」時的侷限。就災害性的氣候參數(如此處的「年平均蝗災次數」及其他如「年平均溫度」、「年平均降雨量」等等)而言,「平均數值」的高低並不重要,重要的是其「高值」,在一年間出現的「頻率」和是否集中。因為,只有發生頻率高,強度大又集中的事件(events),才足以釀成災難。同樣的例子,我的好友,中央研究院汪中和教授,在其研究台灣降雨量時,就曾指出,近年來全台灣地區的「平均降雨量」,並無明顯的改變,但急暴雨的強度和天數,卻明顯的增加和集中了,因此才會醸成許多前所未有的「土石流(泥石流)」災變(包括如前些年「小林村」的不幸悲劇)。

〔承前文 DDS016-「災變氣候」與「中國歷史」(II)〕

前文提到「秦」自統一中國到覆亡,僅僅存活了 15 年(西元前 221 205 年),這似乎也預告了往後中國歷代各王朝,其「興興滅滅」(興起、滅亡)的魔咒和宿命。果不其然,由於氣候的持續惡化,「兩漢」(即「西漢(西元前 206 至西元 25 年)」和「東漢(西元 25 221 年)」)末期,除遭逢大旱和嚴寒的氣候襲虐外,北疆遊牧民族更是不時侵擾進犯,在這種「內外交廹」的情況下,使得「兩漢」王朝疲於奔命,最終還是不敵「天命」,先後分別於西元 25 221 年覆亡。歷史文獻清楚的記載著,西漢末年(西元 17 年),「荊州」地區,發生前所未有的大飢荒(史稱「荊州大飢」),「綠林、赤眉」義軍,群起發難,歷經 8 年,「西漢」亡。無獨有偶,同樣的戲碼、同樣的悲劇又在「東漢」時期上演,史書清楚記載,「東漢」王朝,潰亡於長達 20 年之久(西元 184 204年)的「黄巾之亂」。

為了便於讀者了解自「西漢」以後,歷代王朝興亡和氣候之關連性,我把中國過去兩千年來的「溫度異常曲線」(資料來源:Yang et al.,  Geophys. Res. Lett. 29, doi:10.1029/2001GL014485, 2002 ),依時間尺度疊置於各王朝起迄年代之上(見下圖)。該「溫度異常曲線」咸被認為是,最能代表過去兩千年來,全中國「年平均溫變化」的趨勢,因為它不但整合了來自冰蕊、樹輪、湖泊沉積物的各種溫度指標和歷史文獻記錄,更重要的是它也將一般重建古氣候、古溫度所面臨最困難的「數據時空分佈」問題也儘可能考量進去。


上圖下方橫軸為時間,縱軸為溫度,在溫度為零時的細黑橫線,代表的是平均溫度,而黃色的粗線,代表的則是溫度異常的變化幅度,「正值」表示「熱、暖」,「負值」表示「冷、寒」。由圖可知,全中國在過去兩千年間溫度的變化幅度,大約均在 ± 1.5 oC 之間。不要小看這區區的 ± 1.5 oC,它可是決定了秦統一中國後,兩千多年來所有歷代王朝的興亡,這條「溫度異常曲線」,我在多次的學術公開演講裡,稱之為中國歷史上的「致命曲線」,甚或就是中國的「生命線」。(待續)

2013年6月13日 星期四

DDS016-「災變氣候」與「中國歷史」(II)

承前文 DDS015-「災變氣候」與「中國歷史」(I

時序推移,地表氣候渡過了,持續近五千年的「全新世氣候最適期」後,好日子也就差不多過完了,接下來又回到如同「8,200-年事件」時的冷期,這個冷期持續了約一千伍百多年,到西元前 2,000 年,才又回到另一暖期,但這暖期也是命運多舛,大約在西元前 1,300 年時,又被一短暫的冷期打斷(請參見前文 DDS015 中,1990 IPCC Report 的溫度曲線。)

中國花粉化石的研究進一步指出,從西元前 1,000 770 年,中國也和全球氣候同步,開始進入第一次「中國小冰期」,平均溫度較往常下降了約 1 oC 左右,今天並不結冰的長江和漢水,這時的河面卻都被厚厚的浮冰所覆蓋。這種急遽的氣候惡化,也導致了西元前 858 722 年間的大規模乾旱。事實上,中國歷史上,有文字記載的第一次大規模「蝗災」,即是發生在西元前 707 年(註一:蝗災是氣候惡化的最好指標,因為氣候異常、澇旱交替、四時脫序,最適合其幼虫滋長和漫;註二:歷史上記載大規模「蝗災」之景況,常以「飛蝗敝天」來形容,指的就是當大規模蝗蟲飛越農田時,把太陽也摭蓋掉了,使得白晝頓時變成黑夜,你不要以為這是誇張之辭,前不久,北京沙塵暴來襲時,也是白晝變成黑夜;註三:其過境時的慘況,有詩為證:「飛蝗敝天日無色,野老田中淚垂血,牽衣頓足捕不能,大枝全空小枝折;註四:這種蝗災危害之慘烈,在往後的中國歷史中,屢見不鮮,例如光緒三年(1877年)至四年(1878年)"山西全境大旱,赤地千里,草根樹皮剝掘殆盡,愚民易子而食";註五:中國自古以農立國,對那些以農耕維生的百姓,每天日出起床,眼巴巴望著的,就是那些地上長出來的作物,氣候異常帶來的蝗災肆虐,使得生活頓失依靠,為了苟活,命也可以輍出去,這時只要有人登高一呼,揭桿而起,群起效尤,這也就是為什麼,後來歷史上所謂「農民起義」時,「農民軍」人數動軋百萬計,其中最著名的例子,就是明末李自成滅明所領的義軍,這是後話,就此打住,以後文中再與你詳述。)

這次大規模氣候惡化所帶來的乾旱,連西北塞外的犬戎等遊牧民族,也無法倖免(註:春秋時期,除中原的「華夏農耕民族」外,尚有盤聚四方的戎、狄、蠻、夷四大遊牧民族。依其分佈方位,分別稱為「東夷」,「南蠻」,「西戎」和「北狄」。在「春秋」時期,「戎」和「狄」主要是分布在今黄河流域或更北和西北地區。)由於遊牧民族固有的習性和生活方式,為了掠奪草原(牛、羊、馬放牧所需)、牲口和糧食,便不時大舉入侵中原,這種來自西北塞外遊牧民族的侵擾殺伐,是歷代各王朝揮之不去的夢魘,為了抵禦這些遊牧民族的入侵,從西元前六世紀開始,至十六世紀明朝末年止,整整兩千兩百多年來,歷代皇帝,可以啥都不做,就是不能不修、築「長城」,因為在冷兵器時代,城牆是兩軍對峙時的最重要防禦工事,下面兩幅照片,即是作者多年前造訪西安,在安芝生院士悉心安排下,考察「明城牆」原址(上)及城牆上角樓(下)時所攝。在這「內憂外患」的情況下,逼的「西周」王朝(周平王),不得不於西元前 770 年,將國都由「鎬京」往東遷到「雒邑(今洛陽)」(史學家稱之為「周室東遷」),此後的「周」朝,史學上稱之為「東周」,自此之後,全中國進入了分裂割據,戰亂紛爭不斷的「春秋戰國」時代。



依史書記載,「東周」王朝實則前後可分為「春秋」(西元前 771 475 年)和「戰國」(西元前 475 221 年)兩個截然不同的時期,特別就氣候上來說,「春秋」早、中期較為暖濕,適合農耕,社會也相較融洽、和諧、富足。前文提到的「春秋」(中國第一部編年體的史書),記載的就是從西元前 722 479 年間,發生在這段期間的要事,例如歷史上黃河的第一次改道,即是發生在西元前 602 年。另外,春秋時期,秦、晉兩國為求通好,相約彼此信守「晉飢則秦濟,秦飢則晉濟」的原則,有年晉國舉國大飢荒,秦國依約予以濟助,但過後不久,在西元前 647 年,秦國也鬧了飢荒,請晉國濟糧,晉國不但沒有回報,按約濟助,甚至還阻絶運補,引發秦國不滿,舉兵伐晉,晉國不敵,兵敗國亡,這是中國歷史上第一次,因「災變氣候」所引發的國與國間的戰爭。

延至「春秋」末期,氣候又開始日漸惡化,旱災頻傳,為了糧食、農作和土地的各種因素,使得「魯國」和其他諸侯國間的衝突日益加劇,最後「魯國」國勢一落千丈,名存實亡,歷史也從此正式進入所謂的「戰國」時期,到了「戰國」末期,整個中國更是由「戰國七雄(西方的秦,中原以北的晉,東方的齊、燕,南方的楚、吳、越)」割據分佔。這種氣候持續惡化的情況,直到西元前 221 年,「秦」統一中國後,亦難倖免。儘管「秦」帝國挾其一統中國之勢,內政方面採高壓極權的統治,惡化氣候伴隨而來的大規模飢荒,使得「秦」帝國也只能延續 15 年,就被以「陳勝」和「吳廣」為首,在大澤鄉的起義所推翻(西元前 209 年),這次起義也是中國歷史上,第一次大規模的平民起義。下圖所示,即是將以上所述的主要歷史和氣候事件,依其發生的時間敘列。


既然說到了「春秋戰國」,就容我多講幾句。我個人始終認為,不要小看這個時期,雖然它前後只歷經了 550 年,但對往後整個中國文明思想的奠基和躍進,絶非後來自秦統一中國後,所有歷代王朝,加起來超過 2,200 年的積澱所能比擬。白話點說,「秦」之前這 550 年是「放山雞」,「秦」之後的 2,200 多年則是十足的「來亨雞」,你說:「這是啥意思?」我先不點破,有智慧的你,就自個兒去慢慢細嚼、領悟、體會吧!要不我就建議你,到市場雞販那,問問這兩種雞有何不同?說正經的,今天你的所思、所想、所學、所活,大都受惠於出生在那個大時代的先聖古賢,以及他們歷久彌新的思想和睿智。別的不說,看看這個時期,那些叫得出名號的人物(其人其事):「春秋」時代的「孔子」、神醫「扁鵲」(皇帝內經)、「孫武」(孫子兵法)、吳王「夫差」、越王「句踐」「莊子(莊周)」、「老子(李耳)」(道德經)、「管仲(管子)」、「范蠡(陶朱公)」等;「戰國」時代的「孟子」、名將「吳起」、「孫臏」和「龐涓」、「商鞅」變法、「鬼谷子」(縱橫家鼻祖)、「蘇秦」(合縱)、「張儀」(連橫)、「屈原」、「李冰」(都江堰)、「呂不韋」(呂氏春秋)、「藺相如」、「魯仲連」等。此外,如計算工具「算籌」、「古六曆」和「閏月」、中國古樂的「十二律體」、「詩經」、「尚書」、「山海經」、最早運籌學中的「博弈論」、世上最古老的天文巨著「甘石星經」、地理巨著「禹貢」、計時工具「漏滴(又稱漏刻)」等等,都是「春秋戰國」這個時期的劃時代產物。(待續)

2013年6月10日 星期一

DDS015-「災變氣候」與「中國歷史」(I)

我將本文的題目訂為「災變氣候與中國歷史」,把「災變氣候」和「中國歷史」擺在同等的地位,對我而言,是一種極大的挑戰,也是一種前所未有的大膽嚐試。因為,我們學校所學或平日談論「歷史」的方式,要不就是依循紀元排序的脈絡(如編年史、斷代史等),要不就是專注於特定的主題(如文化史、戰爭史、貨殖史等等),而本文想要傳遞給讀者的信息則是:我們其實也可以,從引發大規模災變的「氣候」因素切入,來重新審視整個中國歷史的框架和進程,屬於一種「巨觀」思維的歷史見解。

尤其是自西元前 221 年,秦統一中國後,兩千多年來,所有歷代王朝的覆亡更迭(即改朝換代),除了大家熟知的各種皇權、朝政、官府等內部問題外,主要還是來自「災變氣候」這個外在的因素。說白了就是:「氣候」打著拍子,「歷史」隨之起舞,成也氣候,敗也氣候。中國歷史中,記述各代帝王的「無道」、「暴虐」或「霸業」、「盛治」,說穿了只是「氣候」搭了舞台,各個帝王視其自個兒能耐,盡情演出罷了。「氣候」好時,老百姓收成好,府庫稅收、糧倉飽足,四處歌功頌德,自是得個「國泰民安」盛世榮景的美名;「氣候」不好時,農作歉收,蝗災肆虐,民不聊生,怨聲四起,自是落得「暴虐無道」、「苛政猛於虎」的下場。在後者的場景下,端看這時舞台上主角(即當時在位的帝王)演出的戲碼如何,要是還是「嬉皮笑臉」,繼續「脫序演出」,下場就明白不過了,不但害了自身,連老祖宗的江山也不得不拱手讓人。要不就是擺姿作態,做出「苦民所苦」之狀(管他是真是假),若罩不住、擺不平,只好再頒個「罪己詔」、「誥天文」,表面上似乎萬分自責,骨子裡是把「老祖宗」和「老天爺」一齊拿來當墊背,唬哢下那些死老百姓,運氣好,也就能蒙混過關,朝代也得以苟延,運氣差,那就只好「改朝換代」了。史磧斑斑,歷歷可考,也就是所謂的「自作孽,猶可違,天作孽,不可活」。從這個角度脈絡來看,整部兩千多年來的「中國歷史」,記錄的其實是一部「中國氣候的災變史」,也就是華夏農耕民族,在中華大地上,所進行的一部「人與天爭的血淚史」。

說到這,我的老毛病又犯了,不得不再話幾句,喜歡我這調調的讀者,拍案叫絕,直說就是這個味,討厭的讀者,就說我又在鬼扯,天馬行空,言不及義,沒點正經的。好在這畢竟是「部落格」文,讓你可以揮灑自如,窩心又自在。我想提醒的只有兩點:(1)凡是「在位子」上的人,真的要注意,在未來面對「極端氣候」,所可能帶來的各種災變,必須提早因應(包括決策面和行動面)。(2)「人定勝天」這些老掉牙的話,說說就好,千萬不要當真(特別對小朋友),整個人類歷史,什麼時候,你見過「人」能勝過「天」的?!我當然知道,這句話在精神面上的意義,但在我們活生生的現實世界裡(特別是小孩子的未來世界裡),還是好好教會他們,什麼叫著務實負責,才是正道。同樣道理,有天你家孩子在學校被打了個黑眼圈,或是玩具或皮球,被其他同學無理霸佔搶走了,回家向你哭訴抱怨,這時我常聽父母開導小孩說:「吃虧就是佔便宜」,小孩聽了,一臉茫然,我更是一頭霧水,眼圈被打的腫黑,玩具或球被搶了,擺明就是吃了「虧」,那來的「佔便宜」?你會問我說:「那我該怎麼說?在文明社會裡,我們總不該以暴制暴,要我家小孩打回去或是搶回來吧?!」坦白講,我也不知道該怎麼說才好,不過有你這種文明父母,我先給你按個「讚」,現今中國社會什麼都不缺,就缺像你這樣文化水平高的父母。但這不是我的重點,我想說的是,許多我們老祖宗留下來的「格言雋語」,其中育涵的「智慧」,你要嘛不說,要說就說清楚,不要只是一時檢現成,拿來唬哢打發你的孩子,他們是永遠搞不懂也學不到什麼的。

閒話已表過,現在就回到正題上來。當地球脫離了「上次冰期最盛期(LGMlast glacial maximum;距今約18,000 年前)」,來到「全新世(Holocene;距今約 10,000 年前)」時,地表氣候開始漸趨暖化,而且平均溫度變化大都維持在 ± 2 oC 之間(見下圖;from IPCC 1990 report)。這「全新世」開始時的 10,000 年前,也標幟著中國古文明,從「舊石器時代(Paleolithic Age)」邁入了「新石器時代(Neolithic Age)」。這地表的溫暖氣候型態,大致維持了兩千多年左右,然後又回到一較冷的時期(古氣候學上稱之為 「8,200 年事件(8,200-year Event)」)。之後,地表氣候又回到一持續長達五千年(距今約 8,000 3,000 年前)的暖期(古氣候學上稱之為「全新世氣候最適期(Holocene Climate Optimum)」)。事實上,我們所熟知的古文明,如「美索布達米亞(Mesopotamian)」、「古埃及」和「古印度」文明,都是在這段期間,開始發軔並衍盛繁榮的。


中國做為一個古文明帝國,自不例外。在這持續五千年之久的「全新世氣候最適期」,研究指出,整片中國大地當時的溫度,比西元 1880 - 1970 年間的平均溫度高約 1.5 - 2 oC。考古場址出土的各種動物骨骸(距今約 6,000 - 5,600 年前),更証實這些動物遺骸,都出現在比牠們目前分佈的區域,更為北移,表示牠們當時生長地方的氣候,比今天為暖。另外,考古學者,在黃河中、下游和淮河流域,也挖掘出了 170 件農耕器具和堆積達一公尺厚的稻穀(距今約 7,000 年前),顯示先民原始社會部落,於此時早已存在。考古的證據進一步顯示,先民的製陶工藝和技術,在「全新世氣候最適期」這段時間裡,有著長足明顯的進步,主要是反應了,在溫暖氣候條件下,有利於農耕、部落社群的發展,進而需要更多能儲存糧食和水的陶器製品。這種陶器製作技術的快速發展,也代表著,中國古文明由「仰韶文化(又稱彩陶文化;距今約 6,000 - 5,500 年前)」步入「龍山文化(又稱黑陶文化;距今約 4,500 - 4,000 年前)」,研究那些刻蝕在陶器外表上的圖騰和文字記述,以及夯土牆的故址,考古學家們認為,這個時期,甚至已有早期初具「城市」規模型態生活方式的出現。

到了「全新世氣候最適期」的後期(距今約 4,500 - 3,000 年前),沿著黃河兩岸地區,始終還是浸潤在溫暖宜人的氣候型態,而中國的第一個王國(即黃帝),也就在西元前 2,697 年時建立,這一年咸被史學家視為是開「中國歷史」的第一年。之後,大約歷經了 600 年的動盪騷亂,在西元前 2070 年,中國第一個王朝(即夏王朝)正式成立,也開啟了往後中國歷史上,各朝代的綿延更迭。也就在這段期間,中國文字也由最早的「象形文字(hieroglyphs; 見下圖;來自「中國象形文字圖解大全」)」演化到後來的文字。有了這些文字的廣泛流傳和使用,中國官府的第一本曆書,即是在西元前 841 年(西周時期)正式發印製的,而最著名的編年史「春秋」,則是於西元前 722 年(東周時期)開始登錄的。有了這些詳實的文字記錄,數千年來的中國歷史中各朝代的興衰,才得以讓我們後人一窺其貌,也提供了本文,探討「災變氣候」對中國歷代王朝,興衰影響的最直接有利的時序記錄。(待續)



2013年6月6日 星期四

DDS014-「Disastrous climate change and the history of China」


註:這篇論文是我多年來,悉心研究「中國歷史」與「氣候變遷」的一些心得,為求審慎負責並便予更多的國際同好、學者、專家分享,謹以英文期刊論文的格式書寫。對於習於中文的讀者,我將於往後的「部落格」文中,以「科普」的方式另予重新整理陳述,敬請期待並不吝惠予指正。

David D. Sheu 

Institute of Marine Geology and Chemistry, National Sun Yat-Sen University, Kaohsiung 804, Taiwan, Republic of China
daviddsheu@gmail.com
  
Abstract

Disastrous climate change accompanying prolonged droughts has been considered to play a key role in the collapse of human societies and ancient civilizations.  By using well-documented historic records and superimposing the years of the rises and falls of all dynasties in Chinese history on the reported temperature anomaly trend during the past two millennia, I show that the successive change of dynasties in Chinese history is no exception to this causative link and the entire history of China can be viewed as a series of devastating climate oscillations in China.  When temperatures plunged sharply from the norm, the long-lived dynasties were all overthrown by rebellions, mostly peasants, fleeing their homelands in search of food sources and shelters when large-scale famine and chaos occurred under such devastating climate conditions.  The shorter-lived dynasties, which represent the most turbulent periods in Chinese history, also all coincided with recurrent severe droughts when temperatures dropped and consistently remained well below the mean during prolonged cold episodes.  The case of China revealed in this study thus provides a real example of the potential threat of disastrous climate change to current and future societal stability and human civilizations.

Introduction

The potential impact of continuing increases in atmospheric CO2 on the future climate has been a subject of intensive studies at different levels (IPCC, 2007). The abrupt and disastrous changes in climate accompanying prolonged droughts have been shown to play key roles in the downfall of ancient Akkadian, Andean, Mesopotamian and Mayan societies and civilizations (Weiss et al., 1993; Hodell et al., 1995; Binford et al., 1997; Cullen, et al., 2000; deMenocal, 2001; Weiss and Bradley, 2001; Hauq et al., 2003). The recorded history of China spans more than 2800 years, and the years of the rises and falls of all dynasties in Chinese history are well documented in chronological order (Feng, 2003; Kuo, 2003). Furthermore, China retains a variety of instrumental meteorological information sources, including the Local Chronicles, the Official Weather Reports and the Official Historical Documents, which can be used to identify extreme climatic events and help establish semi-quantitatively the overall climate variability in China (Wang and Zhang, 1988; Zhang and Crowley, 1989; Zhang, 1991; Song, 2000; Qian and Zhu, 2002; Ge et al., 2003; Qian et al., 2003).  Studies of paleoclimate proxy records derived from ice cores, tree rings, lake sediments, peat cellulose and laminated stalagmites provide further evidence of climate variations in China during the preceding 2-3 millennia (Lin et al., 1995; Sun et al., 1998; Sun, 2000; Wang and Gong, 2000; Wang et al., 2001; Hong et al., 2001; Yang et al., 2002; Paulsen et al., 2003; Tan et al., 2003; Xu, 2003; Yang et al., 2004).

Most of these studies however emphasize only climate fluctuations (mainly cold vs. warm temperatures and/or drought vs. flood) and broad temperature variation trend in China with scant attention to the impact of recurrent disastrous climates on the rise and fall of all dynasties throughout the full history of China. Here I use historic documents and superimpose the years of the rise and fall of each dynasty in Chinese history on the reconstructed “weighted” temperature anomaly trend (Yang et al., 2002) in China during the last two millennia to show that the successive changes of dynasties in Chinese history are, with no exceptions, coherent with a series of disastrous climate events in China, and that the entire history of China can be compiled in the context of disastrous climate changes in China.

Prehistory of China (pre-Qin dynasty)

A sketch of the important historic and climate-mediated events during the ancient Chinese history from 0 to 3,000 BC is presented chronologically in Figure 1. From 4,500 to 3,000 BP, the region along the bank of Huanghe (Yellow River) continued basking in the mild weather, and the first Chinese Kingdom, i.e., Huang-Te, was founded in 2,697 BC (the year generally regarded as the commencing year of Chinese history) (Feng, 2003; Kuo, 2003). After some 600 years of turmoil, the first dynasty of the Chinese empire, i.e. the Xia dynasty, was established in 2,070 BC. During this period, Chinese characters evolved from the earliest forms of hieroglyphs to modern words. The first year documented by the Official Almanac was dated in 841 BC during the Western Zhou dynasty, and the famous ancient chronicle, the Autumn-Spring, began documenting historical records from 722 BC during the Eastern Zhou dynasty (Kuo, 2003). The entire history of China has been well documented in script since then, and the years of the rise and fall of all successive dynasties have been dated in chronological order. Studies of fossil pollens reveal that, from 1,000 to 770 BC, during a cold period classified as the first Chinese Little Ice Age (CLIA I) by paleoclimatologists, the temperature in China plunged ~1.0 oC below average and many areas, including Yangtze and Han rivers, became deeply frozen (Liu, 1994). A rapidly deteriorating climate was evidenced by extended and repeated droughts (from 858 BC to 722 BC), and widespread crop failure and food shortage due to damage by huge swarms of locusts were first reported in 707 BC (Kuo, 2003). These factors led to prolonged violence from devastated peasants and invasion by the nomadic tribes from the north (Hong et al., 2001; Yang et al., 2002), forcing the Western Zhou dynasty to move eastward and ultimately succeed to the Eastern Zhou dynasty in 771 BC. According to historic records, the Eastern Zhou dynasty consisted of two distinct periods: the Spring and Autumn Annals (771-475 BC) and the Warring States Periods (475-221 BC). Historical documents further reveal that the climate was generally warm and wet during the Spring and Autumn Annals. However, towards the end of the period, the mild climate was punctuated by severe droughts. Such hostile climate led to further intense conflicts among various kingdoms and regional warlords and the Spring and Autumn Annals was ultimately succeeded by the Warring States Periods.


Dynastic changes in Chinese history (from the Qin to the Qing dynasty)

The fluctuating climate continued as the Qin dynasty rose to form the first unified Chinese empire in 221 BC. Due to the continuously worsening climate and widespread famine across the county, the Qin dynasty lasted merely 15 years despite its dictatorial rule and was overthrown by rebellions led respectively by Chenshan and Wukuang (Liu, 1994; Feng, 2003; Kuo, 2003). This was the first uprising of devastated peasants (209 BC) against the ruling empire documented in Chinese history (Fig. 1). During the Western Han (206 BC-AD 25) and the Eastern Han (AD 25-AD 221) dynasties, in addition to severe droughts and freezing temperatures, the Chinese empire suffered from invasions of various nomadic tribes along the northern border. The domestic turmoil and diplomatic wrangling together led to the end of the Western Han (AD 25) and the Eastern Han (AD 221) dynasties. Historical documents clearly record a large-scale famine (the Ginzhou famine) occurring in AD 17 until the uprising of the Lulin-Chimei rebellion that ousted the Western Han emperor in AD 25 (Kuo, 2003). From AD 109 to 194, severe weather conditions continued and the Eastern Han dynasty was overthrown by a 20-year rebellion, Huang-Jin, from AD 184 to 204. The Eastern Han dynasty collapsed in AD 221 (Fig. 2).

In this study, I superimpose the years of the rises and falls of all dynasties since the Eastern Han on the “weighted” temperature anomaly trend in China during the past two millennia as reconstructed by (Yang et al., 2002) (Fig. 2). The composite trend is thought to best represent the overall temperature variations in China because it is constructed by combining multiple paleoclimate proxy records obtained from ice cores, tree rings, lake sediments and historical documents, and takes into account the uneven spatial and temporal distribution of proxy records. As depicted, temperatures in China were above the mean between AD 0-250 with two peaks—one occurring around AD 25 and the other in AD 100-250—then decreased rapidly and stayed mostly below the mean until AD 600. From AD 600 to 1400, temperatures in China are characterized by decadal to centennial variability around the mean but the climate was noticeably punctuated with several severe cold periods centered around AD 900, 1150, and 1300. From AD 1400 to 1920, China entered the so-called Little Ice Age period, with prominent cold peaks around AD 1500, 1650 and 1850. Since the AD 1920s, temperatures have been rising rapidly. The rapid transitions between cold and warm periods over the past 2000 years that are revealed by this anomaly trend broadly match the winter half-year temperature fluctuations in the middle and lower reaches of the Yellow and Yangtze Rivers reconstructed by Ge et al. (2003) using phenological cold/warm events recorded in Chinese historical documents.


Figure 2 (above) further shows that, without exception, all major dynasties collapsed and were overthrown by rebellions during times when temperatures dropped sharply, namely, the Western Han dynasty (202 BC- AD 25) by the Lulin-Zhimei rebellion (AD 21-25), the Eastern Han dynasty (AD 25-220) by the Huang-Jin rebellion (AD 184-204), the Tang dynasty (AD 617-907) by the Huang-Chao rebellion (AD 867-884), the Yuan dynasty (AD 1279-1367) by the Hong-Jin rebellion (AD 1351-1367) and the Ming dynasty (AD 1367-1644) by the Zhang and Li (AD 1630-1644) rebellions. It also shows that the short-lived dynasties from 221 to 617 AD, including the Three Kingdoms (AD 221-263), Wei (AD 263-280), Western Jin (AD 280-316) and Eastern Jin (AD 316-417), Northern and Southern Dynasties (AD 417-589), Sui (AD 589-617) and the Five Dynasties and Ten Kingdoms (AD 907-960)—the most turbulent periods in Chinese history—all coincided with severe droughts and cold episodes when temperatures were well below the mean. The pronounced cold spells during the Northern and Southern Dynasties (AD 417-589), the late Tang dynasty and the mid-Ming dynasty are revealed by the 2,650-year stalagmite record from Shihua Cave, Beijing, China (Tan et al., 2003). The prolonged cold phases during the Ming and early Qing dynasties with the three prominent cold peaks (Fig. 2) are commonly referred to the Chinese Little Ice Age IV to VI (CLIA IV-VI) (Liu, 1994; Lin et al., 1995; Wang et al., 2001; Qian and Zhu, 2002) that occurred between fifteenth and nineteenth century. The three cold peaks shown in Figure 2 are also identified in the 1,270-year high-resolution d18O stalagmite record from Buddha Cave, China (Paulsen et al., 2003).

A conceptual model for understanding the dynastic changes

Figure 3 depicts a conceptual model for helping explain how severe climate variability could have affected prehistoric China and the dynastic changes in modern Chinese history. The model emphasizes the importance of the physiography of China (Zhang and Crowley, 1989; Sun et al., 1998; Sun, 2000). The present-day China borders span 74oE to 135oE and 18oN to 53oN, covering a vast land mass of ~9.6 x 106 km2 that stretches over 5,200 km from east to west and over 5,500 km from north to south. Two-thirds of the total land area is occupied by high mountain ranges, hills, plateaus and deserts in the north and west, while eastern and southern China is predominated by lowlands and plains. Because of China’s extensive territory and complex geomorphology, the climate in China is highly variable and diversified.  With the additional effect of alternating dry and wet monsoons, the climate in China can be divided diagonally from northeast to southwest into two highly contrasting patterns: the western and northwestern part of the country is dominated by dry, cold weather, while eastern and southeastern China is mostly wet and warm. The climatic divide in China preordains the dynastic succession from the west to the east (e.g., the Western Zhou to the Eastern Zhou, the Western Han to the Eastern Han, and the Western Jin to the Eastern Jin dynasties) and from the north to the south (e.g., the Northern Song to the Southern Song dynasties). This is owing to the fact that when the climate starts to deteriorate, it always begins from the northern and western parts of China, then spreads southeastwardly across the entire country.


The contrasting climate patterns have also led the ancient Chinese to develop two distinct living styles and types of settlements, namely (1) the agriculture-oriented Han race that nurtured ancient Chinese civilization around the middle reach of the Huang He (Yellow River) in the central part of China and established the first Chinese empire (i.e., the Xia dynasty) in 2,070 BC, and (2) the nomadic tribes that occupied and roamed the northern and western parts of China. When the climate was mild, the nomadic tribes settled separately from and at peace with the Han race. Once the climate deteriorated, however, the nomads were forced to cross borders to invade the Chinese empire for food sources and shelters. The conflicts between nomadic tribes and the Chinese empire have pervaded Chinese history, including the most famous example that lasted nearly 120 yr (AD 316 to 436) of the attacks by the five major nomadic tribes (the Shung-Ru, Shang-Bei, Jei, Dee and Zharng) along the northern border of the Eastern Jin dynasty (Feng, 2003; Kuo, 2003). Additional examples of invasions by nomads include those by Zhi-Dan and Ru-Jen during the Northern Song dynasty and by the Mongolians during the late Ming dynasty (Liu, 1994). The endless confrontation is evidenced by the construction of the Great Wall, which was intended to be used for protecting the northern borders of the Chinese empire from invasion by nomads and had a history of more than 2,200 yr of construction from individual, small defensive fortifications built in the 6th century BC to its present-day length of over 6,700 km in the AD 16th century during the Ming dynasty (Fig. 1).

As can be seen in Figure 2, all of these turbulences coincide with the most devastating climates in Chinese history. The rapidly deteriorating climate conditions have resulted in widespread crop failures and subsequent large-scale famines in the homeland ruled by Chinese emperors, and consequently effectuated war and conflict between the Han race and various nomadic tribes along the northern and western borders. Indeed, the wars, starvation and epidemics led to the two worst demographic disasters in Chinese history during the Yuan dynasty (13th-14th century) and the late Ming dynasty (AD 1620-1650), in which the population declined sharply by 50% (~55 million decline) and 43% (~70 million decline), respectively (Zhang et al., 2007). During these critical periods of time, as long as someone (e.g., the leaders of rebellions) advocated violence to challenge the sovereign of the ruling emperor, the massive number of refugees would quickly join together as rebellions and jeopardize the governance of the Chinese empire. The turmoil would further worsen the political stability of an empire already plagued by corruption, persecution and incapable rule.  In the end, the ruling emperor would be disposed of and replaced by a new dynasty. Such cause-and-effect repeats throughout the entire history of China. It thus appears that riots instigated by rebellions and invasions by nomads, both mediated largely by disastrous climate changes, are two major causes responsible for successive changes of dynasties in Chinese history and that disastrous climate change plays a key role in the shaping of the history of China.

Conclusion

Upon close examination of Chinese history in conjunction with associated climate oscillations, the succession of dynastic regimes throughout the history of China should be viewed from a global perspective to provide a better understanding of the potential threat of climate change to current and future societal stability and human civilization. This study shows that the entire history of China can be compiled in accordance with the associated series of disastrous climate changes in China.  More specifically, this study shows that the link between climate change and the rise and fall of each dynasty from Western Zhou (771 BC) to Ming (AD 1,644) through the history of China is not correlative but rather causative, as each dynasty was demolished by a rebellion arising due to severe climate changes.

We live in a shrinking world. Any regional geopolitical instability due to hostile climate changes may heighten a nation’s level of tension with neighboring countries as well as pose a threat to the lives and welfare of humankind. Although we are living in an era that is very different from ancient times and modern advancement of science and technology has advanced our flexibility to respond to climate changes, lessons can still be learned from the climate-mediated rise and fall of dynasties occurring throughout the history of China.

Acknowledgements

I thank S. W. Wang, D. Zhang and A. E. Sheu for constructive discussion and providing valuable references and W. P. Hou for preparing figures. This manuscript was benefited greatly by the critical reviews and comments by D. J. Meltzer and M. Williams.  I am also indebted greatly to the late C. C. Biq and T. S. Liu for their moral support and inspiration.

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Figure Captions

Fig. 1. Important historic and climate-mediated events during the ancient Chinese history from 0 to 3000 BC.

Fig. 2. The correlation between the dynastic changes in Chinese history and the reconstructed temperature anomaly trend in China during the last two millennia (see details in text). The temperature anomaly trend is redrawn from Yang et al. (2002).  Bold vertical dash lines mark the years of the beginning and the end of each major dynasty, whereas thin dotted lines denote the short-lived dynasties, the Three Kingdoms (AD 221-263), Wei (AD 263-280), Western (AD 280-316) and Eastern (AD 316-417) Jin, Northern and Southern Dynasty (AD 417-589), and Sui (AD 589-617), in chronological order. Separation of the Song dynasty into the Northern and Southern Song in AD 1,127 is also marked by a thin dotted line. FDTK stands for the Five Dynasties and Ten Kingdoms (AD 907-960). The zero horizontal line (thin dashed) is the mean temperature anomaly trend of the reconstructed series. Names and durations of rebellions that lead to the fall of each dynasty are shown on the top of the panel. Also shown are the durations of the three major cold episodes known as Chinese Little Ice Ages (CLIA IV to VI).

Fig. 3. The conceptual model used in this study for understanding the role of severe climate fluctuations in ancient Chinese civilization and the collapse of each dynasty throughout the entire history of China.