火山爆發改變人類歷史

原文網址：www.sciencedaily.com/releases/2015/07/150708133858.htm

Volcanic eruptions that changed human history

Researchers find new evidence that large eruptions were responsible for cold temperature extremes recorded since early Roman times

火山爆發改變人類歷史

研究人員發現新的證據顯示自羅馬時代早期以來，歷史紀錄中的極端寒冷事件的罪魁禍首為大型火山噴發

It is well known that large volcanic eruptions contribute to climate variability. However, quantifying these contributions has proven challenging due to inconsistencies in both historic atmospheric data observed in ice cores and corresponding temperature variations seen in climate proxies such as tree rings.

眾所皆知的是，大型火山噴發會導致氣候動盪。然而，要定量化它們的影響卻相當困難，這是由於從冰心中觀察到的大氣成分歷史紀錄，對應到樹輪這類氣候指標中的溫度變化紀錄時，會有不一致的情形發生。

Published today in the journal Nature, a new study led by scientists from the Desert Research Institute (DRI) and collaborating international institutions, resolves these inconsistencies with a new reconstruction of the timing and associated radiative forcing of nearly 300 individual volcanic eruptions extending as far back as the early Roman period.

刊登於今日《自然》(Nature)期刊上的新研究中，科學家以新方法重建了最早可追溯至羅馬時代早期的300次火山噴發事件的發生時間與相關輻射驅動力(radiative forcing)，而解決了這些不一致。本研究由沙漠研究中心(Desert Research Institute，DRI)的科學家協同其他國際機構的科學家進行。

"Using new records we are able to show that large volcanic eruptions in the tropics and high latitudes were the dominant drivers of climate variability, responsible for numerous and widespread summer cooling extremes over the past 2,500 years," said the study's lead author Michael Sigl, Ph.D., an assistant research professor at DRI and postdoctoral fellow with the Paul Scherrer Institute in Switzerland.

「利用這些新紀錄，我們可以顯示熱帶與高緯度區域的大型火山噴發事件為氣候變化的主要推手，導致了過去2,500年來許多次的大規模極端冷夏，」此研究的第一作者Michael Sigl博士說，他是DRI的研究助理教授及瑞士保羅謝爾研究所(Paul Scherrer Institute)的博士後研究員。

"These cooler temperatures were caused by large amounts of volcanic sulfate particles injected into the upper atmosphere," Sigl added, "shielding the Earth's surface from incoming solar radiation."

「這些比平常還要低的溫度的肇因為火山往高層大氣噴射的大量硫酸鹽粒子。」Sigl補充，「它們會阻擋地表接收來自太陽的輻射。」

The study shows that 15 of the 16 coldest summers recorded between 500 BC and 1,000 AD followed large volcanic eruptions -- with four of the coldest occurring shortly after the largest volcanic events found in record.

此研究顯示從西元前1,500年至西元1,000年間記錄到的16次最冷夏季中，有15次發生在大型火山噴發之後—其中最冷的四次緊接在紀錄中最大的火山噴發事件過後。

This new reconstruction is derived from more than 20 individual ice cores extracted from ice sheets in Greenland and Antarctica and analyzed for volcanic sulfate primarily using DRI's state-of-the-art, ultra-trace chemical ice-core analytical system.

這些新的重建結果建立於DRI最先進的超微量化學冰芯分析系統(ultra-trace chemical ice-core analytical system)，對採自格陵蘭與南極冰層的二十幾根冰芯中火山硫酸鹽的分析結果。

These ice-core records provide a year-by-year history of atmospheric sulfate levels through time. Additional measurements including other chemical parameters were made at collaborating institutions.

這些冰芯可以提供過往大氣中硫酸鹽含量的年度紀錄。包括其他化學指標的更多測量則由其他合作機構進行。

"We used a new method for producing the timescale," explained Mai Winstrup, Ph.D., a postdoctoral researcher at the University of Washington, Seattle. "Previously, this has been done by hand, but we used a statistical algorithm instead. Together with the state-of-the-art ice core chemistry measurements, this resulted in a more accurate dating of the ice cores."

「我們利用新的方法來建立時間序列。」西雅圖華盛頓大學(University of Washington, Seattle)的博士後研究員，Mai Winstrup博士說。「過往這得以人工來完成，但現在我們改用統計演算法，加上最先進的冰芯化學測量技術，我們得以對冰芯做出更精準的定年。」

"Using a multidisciplinary approach was key to the success of this project," added Sigl

「採用跨領域的研究方法為這項計畫的成功關鍵。」 Sigl補充。

In total, a diverse research group of 24 scientists from 18 universities and research institutes in the United States, United Kingdom, Switzerland, Germany, Denmark, and Sweden contributed to this work -- including specialists from the solar, space, climate, and geological sciences, as well as historians.

總的而言，這個多元化的研究團隊包含了18所大學及研究機構的24名科學家，分別來自美國、英國、瑞士、德國、丹麥與瑞典。這些專家的研究領域包含了太陽能、宇宙、氣候、地質與歷史。

The authors note that identification of new evidence found in both ice cores and corresponding tree rings allowed constraints and verification of their new age scale.

作者強調從冰芯與對應的樹輪辨識出來的新證據，可以用來界定與証實他們新建立的時程表。

"With the discovery of a distinctive signature in the ice-core records from an extra-terrestrial cosmic ray event, we had a critical time marker that we used to significantly improve the dating accuracy of the ice-core chronologies," explained Kees Welten, Ph.D., an associate research chemist from the University of California, Berkeley.

「從冰芯紀錄中發現的來自地外宇宙射線事件的獨特訊號，可以當作特定的時間標記，讓我們大幅增加冰芯定年的精準度。」Kees Welten博士說，他是加州大學柏克萊分校(University of California, Berkeley)的化學副研究員。

A signature from this same event had been identified earlier in various tree-ring chronologies dating to 774-775 Common Era (CE).

在定年結果為公元774至775年的許多樹輪中，於更早之前也有辨識出同一事件的訊號。

"Ice-core timescales had been misdated previously by five to ten years during the first millennium leading to inconsistencies in the proposed timing of volcanic eruptions relative to written documentary and tree-ring evidence recording the climatic responses to the same eruptions," explained Francis Ludlow, Ph.D., a postdoctoral fellow from the Yale Climate & Energy Institute.

「過往定年第一個千禧年間的冰芯時會有五到十年的誤差，這會造成冰芯顯示的火山爆發時間，與歷史文獻及樹輪紀錄中由同一事件造成的氣候變化時間，兩者之間出現不一致的情形。」耶魯大學氣候能源研究中心(Yale Climate & Energy Institute)的博士後研究員，Francis Ludlow說。

Throughout human history, sustained volcanic cooling effects on climate have triggered crop failures and famines. These events may have also contributed to pandemics and societal decline in agriculture-based communities.

綜觀人類的歷史，持續的火山冷卻效應對氣候的影響會導致作物歉收與饑荒。這些事件可能會造成農業社會爆發瘟疫與社會衰敗。

Together with Conor Kostick, Ph.D. from the University of Nottingham, Ludlow translated and interpreted ancient and medieval documentary records from China, Babylon (Iraq), and Europe that described unusual atmospheric observations as early as 254 years before Common Era (BCE). These phenomena included diminished sunlight, discoloration of the solar disk, the presence of solar coronae, and deeply red twilight skies.

協同諾丁漢大學(University of Nottingham)的Conor Kostick博士，Ludlow翻譯與解讀來自中國、巴比倫(伊朗)與歐洲各地古代及中世紀文獻中，所描述的異常大氣現象。這些文本的年代最早可追溯至公元前254年。異常大氣現象包括陽光減弱、日輪(solar disk)顏色異常、肉眼可見日冕以及深紅色的日暮。

Tropical volcanoes and large eruptions in the Northern Hemisphere high latitudes (such as Iceland and North America) -- in 536, 626, and 939 CE, for example -- often caused severe and widespread summer cooling in the Northern Hemisphere by injecting sulfate and ash into the high atmosphere. These particles also dimmed the atmosphere over Europe to such an extent that the effect was noted and recorded in independent archives by numerous historical eyewitnesses.

像是發生在公元536年、626年及939年的熱帶或北半球高緯地區(如冰島與北美)的大型火山噴發，會往高層大氣噴出大量的硫酸鹽與火山灰，經常導致北半球發生大區域的嚴酷冷夏。這些粒子也會造成歐洲上空的大氣變得十分朦朧不清，而被歷史上的許多人目擊，記載在各自獨立的文獻中。

Climatic impact was strongest and most persistent after clusters of two or more large eruptions.

連續二個或以上的大型噴發會對氣候造成最強烈與最持久的影響。

The authors note that their findings also resolve a long-standing debate regarding the causes of one of the most severe climate crises in recent human history, starting with an 18-month "mystery cloud" or dust veil observed in the Mediterranean region beginning in March, 536, the product of a large eruption in the high-latitudes of the Northern Hemisphere.

作者認為他們的發現也解決了長久以來，對人類近代史中最嚴重的氣候危機之一的成因的爭論。此事件始於從西元536年三月開始，在地中海地區觀察到長達18個月的「神秘雲」或塵罩，其為北半球高緯度地區的大型噴發事件產物。

The initial cooling was intensified when a second volcano located somewhere in the tropics erupted only four years later. In the aftermath, exceptionally cold summers were observed throughout the Northern Hemisphere.

僅僅四年後，發生在某個熱帶地區的另一次火山噴發，加強了最初的冷化現象。結果導致了整個北半球地區都能觀察到的異常冷夏。

This pattern persisted for almost fifteen years, with subsequent crop failures and famines -- likely contributing to the outbreak of the Justinian plague that spread throughout the Eastern Roman Empire from 541 to 543 CE, and which ultimately decimated the human population across Eurasia.

這種氣候模式持續了將近15年之久，伴隨而來的作物歉收與飢荒可能導致了公元541年至543年，襲捲東羅馬帝國全境的查士丁尼瘟疫(Justinian plague)，最終導致歐陸人口的銳減。

"This new reconstruction of volcanic forcing will lead to improved climate model simulations through better quantification of the sensitivity of the climate system to volcanic influences during the past 2,500 years," noted Joe McConnell, Ph.D., a DRI research professor who developed the continuous-flow analysis system used to analyze the ice cores.

「透過更精確的定量過去2,500年間氣候系統受火山活動的影響程度，這項重建火山活動的全新結果可以改良氣候模型的模擬成效。」DRI的研究教授，Joe McConnell博士指出，他發展出用來分析冰芯的連續流動分析系統。

"As a result," McConnell added, "climate variability observed during more recent times can be put into a multi-millennial perspective -- including time periods such as the Roman Warm Period and the times of significant cultural change such as Great Migration Period of the 6th century in Europe."

「結果上而言，」McConnell補充，「我們應將最近觀測到的氣候變化納入數千年的尺度中，這段時期包括了像是羅馬溫暖期(Roman Warm Period)以及某些重大的文化變遷時期，如發生在6世紀時的歐洲民族大遷徙時期(Great Migration Period)。」

This reconciliation of ice-core records and other records of past environmental change will help define the role that large climatic perturbations may have had in the rise and fall of civilizations throughout human history.

化解冰芯紀錄與其他過去環境變遷的紀錄之間的不一致，有助於確立在人類歷史裡，強烈的氣候變動在文明的興衰中扮演何種角色。

"With new high-resolution records emerging from ice cores in Greenland and Antarctica, it will be possible to extend this reconstruction of volcanic forcing probably all the way back into the last Ice Age," said Sigl.

「有了來自格陵蘭與南極冰芯中的高解析紀錄，我們或許能重建遠至上次冰河期的火山作用。」Sigl說。

This research was largely funded by the U.S. National Science Foundation's Polar Program; with contributions from additional funding agencies and institutions in Belgium, Canada, China, Denmark, France, Germany, Iceland, Japan, Korea, The Netherlands, Sweden, Switzerland, and the United Kingdom.

此研究大部分由美國國家基金會的極地計畫資助，其他資金來源包括比利時、加拿大、中國、丹麥、法國、德國、冰島、日本、韓國、荷蘭、瑞典、瑞士及英國的資金補助機構與研究機構。

引用自：Desert Research Institute. "Volcanic eruptions that changed human history: Researchers find new evidence that large eruptions were responsible for cold temperature extremes recorded since early Roman times." ScienceDaily. ScienceDaily, 8 July 2015.