許多瀕臨滅絕的物種有可能未留下化石紀錄就此消失

原始網址：www.sciencedaily.com/releases/2016/03/160321200445.htm

Many species now going extinct may vanish without a fossil trace

Human-made 'sixth extinction' may seem small compared to five prehistoric die-offs

許多瀕臨滅絕的物種有可能未留下化石紀錄就此消失

人類導致的第六次大滅絕規模與前五次史前大滅絕相比看似小了許多

Scientists struggle to compare the magnitude of Earth's ongoing sixth mass-extinction event with the five great die-offs of prehistory. A new study by three paleontologists shows that the species now perishing may vanish without a permanent trace -- and earlier extinctions may be underestimated as well.

科學家力圖比對地球上正在發生的第六次大滅絕和前五次史前大滅絕事件之間的差異。一項由三位古生物學家進行的新研究顯示，現今的瀕危物種可能不留下一絲能保存良久的記錄便就此消失，而我們或許也低估了過往大滅絕事件的規模。

"Comparing the current biodiversity crisis, often called the 'sixth extinction,' with those of the geological past requires equivalent data," says Roy Plotnick, professor of earth and environmental sciences at the University of Illinois at Chicago.

「我們需要對等的資料才能將現今發生的生物多樣性危機，又稱『第六次大滅絕』跟地質史上的其他次滅絕事件互相比較。」芝加哥伊利諾大學的地球與環境科學教授 Roy Plotnick說。

He and two colleagues compared the "Red List" of endangered species with several ecological databases of living species and three paleontological databases of catalogued fossils. They ran a statistical analysis to indicate which threatened species were most likely to disappear with no mark of their existence.

他和另外兩外同僚比對了編列瀕危物種的「紅皮書」(Red List)、數個紀錄現存動物的生態資料庫，以及三個記載已編目化石的古生物資料庫。接著他們進行統計分析以找出哪些受威脅的物種最有可能不留下牠們曾經存在的痕跡而永遠消失。

The researchers were shocked to find that more than 85 percent of the mammal species at high risk of extinction lack a fossil record. Those at highest risk have about half the probability of being incorporated into the fossil record compared to those at lower risk.

研究人員相當驚訝地發現高度瀕危的哺乳類物種中有85%以上會缺乏化石紀錄。面臨最高瀕危風險的物種成為化石紀錄一部分的機率，比那些處在較低風險的物種形成化石的機率低了一半。

Animals least likely to be found as fossils are "the small, cute and fuzzy ones, like rodents and bats," Plotnick said. "Body size is an obvious factor -- bigger things tend to leave a fossil record, as do things with larger geographical ranges."

動物中最難發現的化石便是那些「小巧可愛、毛茸茸的動物，像是齧齒類和蝙蝠」。 Plotnick說。「體型是相當明顯的要素，大型物種比較容易留下化石紀錄，而那些地理分布比較廣的也是。」

Viewed from the perspective of the fossil record alone, the magnitude of the current mammal die-off thus appears markedly reduced. The picture may be even more distorted for other land-dwelling vertebrates: only 3 percent of today's threatened bird species and 1.6 percent of threatened reptile species have a known fossil record.

若僅由化石紀錄的觀點來看，當今哺乳類的滅絕規模會顯得輕微了許多。對於其他陸生脊椎動物而言，從同樣的觀點出發可能會更加曲解牠們面臨的滅絕困境。今日備受威脅的鳥類中只有百分之3留下了為人所知的化石紀錄；而爬蟲類更是只有百分之1.6。

Comparing the scale of the current extinction episode, which is based primarily on terrestrial vertebrates, to earlier extinctions that are mostly calculated from the fossil record of hard-shelled marine invertebrates, is particularly problematic, Plotnick said, although ancient extinctions may also be underestimated by contemporary paleontologists.

Plotnick說現行的滅絕事件主要對象是陸生脊椎動物，然而過去滅絕事件的規模大多是利用具有硬殼的海生無脊椎動物化石紀錄來估算，因此要比較兩者的規模就會特別有問題。而現代的古生物學家也可能低估了古代滅絕事件的規模。

Nevertheless, fossils will provide the only reliable record of life on Earth for posterity.

然而，化石終究是地球生命留給後裔的紀錄中唯一可靠的。

"There are species going extinct today that have never been described," Plotnick said. "Others are going extinct that are known only because someone wrote it down." All such species would thus be unknown in the far future, he said, if the written historical record is lost -- as it might well be.

「今日許多邁向滅亡的物種是人們從來沒有記述到的。」 Plotnick說。「而其他消失的物種能夠為人所知僅僅是因為有人將牠書寫下來。」如果這些歷史文字紀錄消失，那麼所有這類物種在遙遠的未來都將被淡忘，而這確實很有可能發生，他說。

The fossil record, Plotnick points out, is much more durable than any human record.

Plotnick指出化石紀錄遠比人類所有的紀錄方式禁得起時間考驗。

"As humanity has evolved, our methods of recording information have become ever more ephemeral," he said. "Clay tablets last longer than books. And who today can read an 8-inch floppy?" he shrugged. "If we put everything on electronic media, will those records exist in a million years? The fossils will."

「隨著人類的進步，我們保存資訊的方式卻顯得越來越稍縱即逝。」他說。「泥片(clay tablet，巴比倫人將文字刻於其上)可以比書本流傳的更久。而今日又有誰能讀取8吋磁碟片？」他聳聳肩。「如果我們將所有事物都保存在電子裝置中，這些檔案可以存在百萬年之久嗎？無庸置疑的是化石絕對可以。」

Other authors on the study, published earlier this month in Ecology Letters, are Felisa A. Smith of the University of New Mexico and S. Kathleen Lyons of the National Museum of Natural History in Washington, D.C.

此篇本月稍早刊登於《生態學通訊》的論文的其他作者還包括了新墨西哥州大學的 Felisa A. Smith，以及華盛頓國立自然歷史博物館的 S. Kathleen Lyons。

引述自：University of Illinois at Chicago. "Many species now going extinct may vanish without a fossil trace: Human-made 'sixth extinction' may seem small compared to five prehistoric die-offs." ScienceDaily. ScienceDaily, 21 March 2016. 

分析遠達50億年前的氣候變遷

原文網址：www.sciencedaily.com/releases/2016/03/160316082942.htm

Climate variations analyzed five million years back in time

分析遠達50億年前的氣候變遷

When we talk about climate change today, we have to look at what the climate was previously like in order to recognise the natural variations and to be able to distinguish them from the human-induced changes. Researchers from the Niels Bohr Institute have analysed the natural climate variations over the last 12,000 years, during which we have had a warm interglacial period and they have looked back 5 million years to see the major features of the Earth's climate. The research shows that not only is the weather chaotic, but the Earth's climate is chaotic and can be difficult to predict. The results are published in the scientific journal, Nature Communications.

當我們討論眼下發生的氣候變遷時，我們必須要先研究過去的氣候是如何，這樣才能了解在自然情況下的氣候變化，而能夠與人類引發的變動之間做出區隔。波爾研究所的研究人員分析了過去12,000年以來，我們所處的溫暖間冰期中的自然氣候變化；他們同時也回顧了過去50億年以了解地球氣候的諸多重要特徵。研究顯示變化莫測的不只是天氣，地球氣候也是如此因而難以被人們預測。這項結果刊登於科學期刊《自然通訊》(Nature Communications)之上。

The Earth's climate system is characterised by complex interactions between the atmosphere, oceans, ice sheets, landmasses and the biosphere (parts of the world with plant and animal life). Astronomical factors also play a role in relation to the great changes like the shift between ice ages, which typically lasts about 100,000 years and interglacial periods, which typically last about 10-12,000 years.

地球氣候系統的重要特徵便是大氣、海洋、冰層、陸塊和生物圈(地球有動植物生活的部分)彼此之間複雜的交互作用。來自宇宙的因子也會參與一些重大的變動，像是冰期和間冰期的交替。前者通常會持續約100,000年，後者則通常歷時10至12,000年。

Climate repeats as fractals

氣候就像碎形(fractal)般不斷地重複

"You can look at the climate as fractals, that is, patterns or structures that repeat in smaller and smaller versions indefinitely. If you are talking about 100-year storms, are there then 100 years between them? -- Or do you suddenly find that there are three such storms over a short timespan? If you are talking about very hot summers, do they happen every tenth year or every fifth year? How large are the normal variations? -- We have now investigated this," explains Peter Ditlevsen, Associate Professor of Climate Physics at the Niels Bohr Institute at the University of Copenhagen. The research was done in collaboration with Zhi-Gang Shao from South China University, Guangzhou in Kina.

「你可以把氣候視作一種碎形，這種結構或模式會不斷地以越來越小的形式重複出現。如果你討論到百年強度的風暴，那麼在兩次事件之間的100年內還會再次出現這麼強的風暴嗎？或者你會突然發現在一段相當短的期間內就發生了三次強度相當的風暴？如果你提及了數個非常炎熱的夏季，那麼它們是每十年還五年就會發生一次嗎？『正常』的變化幅度究竟有多大？這是我們目前正在探討的。」哥本哈根大學波爾研究所的氣候物理學副教授 Peter Ditlevsen解釋。此研究在中國廣州南中國大學的 Zhi-Gang Shao協助下完成。

The researchers studied temperature measurements over the last 150 years, ice core data from Greenland from the interglacial period 12,000 years ago, for the ice age 120,000 years ago, ice core data from Antarctica, which goes back 800,000 years, as well as data from ocean sediment cores going back 5 million years.

研究人員探討了過去150年來的氣溫測量結果，和格陵蘭12,000年來的間冰期冰芯紀錄；而12萬年前的冰河期則以南極洲冰芯判讀，這最遠能追溯至80萬年前，最後還有可以回溯至50億年前的海洋沉積物岩芯資料。

"We only have about 150 years of direct measurements of temperature, so if, for example, we want to estimate how great of variations that can be expected over 100 years, we look at the temperature record for that period, but it cannot tell us what we can expect for the temperature record over 1000 years. But if we can determine the relationship between the variations in a given period, then we can make an estimate. These kinds of estimates are of great importance for safety assessments for structures and buildings that need to hold up well for a very long time, or for structures where severe weather could pose a security risk, such as drilling platforms or nuclear power plants. We have now studied this by analysing both direct and indirect measurements back in time," explains Peter Ditlevsen.

「我們僅僅擁有大約150年的氣溫直接測量紀錄，因此舉例來說，若我們想要預估在100年內氣溫的變化幅度可以有多大，我們就能參照這段時期的氣溫紀錄，但如果我們想要從1000年的氣溫資料中獲取任何訊息時，前述的百年紀錄就派不上用場了。然而若我們可以確知給定一段時間，當中的變化幅度就會有多大，那這種關係就可以讓我們作出預估。這種預測對於建築物或設施的安全評估來說相當重要，尤其是那些必須要長期維持在良好狀態，或是可能會面臨造成安全損害的惡劣天氣的建物或設施，像是鑽油平台或核電廠。我們現在利用分析過往的直接和間接測量記錄來研究這項議題。」 Peter Ditlevsen解釋。

The research shows that the natural variations over a given period of time depends on the length of this period in the very particular way that is characteristic for fractals. This knowledge tells us something about how big we should expect the 1000-year storm to be in relation to the 100-year storm and how big the 100-year storm is expected to be in relation to the 10-year storm. They have further discovered that there is a difference in the fractal behaviour in the ice age climate and in the current warm interglacial climate.

研究顯示在一段時間內的自然變動幅度取決於這段時間的長短，這種關係跟碎形的特徵十分相似。這項知識告訴我們千年強度的風暴會有多強，跟百年強度的風暴規模之間有所關聯；而百年強度的風暴會有多強，又跟十年強度的風暴規模之間有所關聯。他們更進一步的發現冰河期氣候的碎形行為，與目前溫暖間冰期氣候的碎形行為兩者之間有所不同。

Abrupt climate fluctuations during the ice age

冰河期的急遽氣候波動

"We can see that the climate during an ice age has much greater fluctuations than the climate during an interglacial period. There has been speculation that the reason could be astronomical variations, but we can now rule this out as the large fluctuation during the ice age behave in the same 'fractal' way as the other natural fluctuations across the globe," Peter Ditlevsen.

「我們可以看到冰河期時的氣候波動與間冰期的相比大了許多。之前有人猜測原因可能跟天文因子的變化有關，但我們現在可以排除這個可能性，因為冰河期內發生的大型波動，就『碎形』行為來說跟全球其他自然因子的變動一模一樣。」 Peter Ditlevsen說。

The astronomical factors that affect the Earth's climate are that the other planets in the solar system pull on the Earth because of their gravity. This affects the Earth's orbit around the sun, which varies from being almost circular to being more elliptical and this affects solar radiation on Earth. The gravity of the other planets also affects the Earth's rotation on its axis. The Earth's axis fluctuates between having a tilt of 22 degrees and 24 degrees and when the tilt is 24 degrees, there is a larger difference between summer and winter and this has an influence on the violent shifts in climate between ice ages and interglacial periods.

會影響地球氣候的天文因素像是地球會因為太陽系其他行星的重力而受到牽引，這會影響地球環繞太陽的軌道，使得它會在近乎圓形與傾向橢圓之間來回擺盪，進一步地影響地球受到的日照量。其他行星的重力也會施加在地軸上而影響地球自轉。地球自轉軸的角度會在22至24度之間擺動，當地軸傾斜24度時，夏季和冬季之間的差異便會增加，這造成的劇烈氣候變化使得冰河期和間冰期交替出現。

The abrupt climate changes during the ice age could be triggered by several mechanisms that have affected the powerful ocean current, the Gulf Stream, which transports warm water from the equator north to the Atlantic, where it is cooled and sinks down into the cold ocean water under the ice to the bottom and is pushed back to the south. This water pump can be put out of action or weakened by changes in the freshwater pressure, the ice sheet breaking up or shifting sea ice and this results in the increasing climatic variability.

冰河期時的急遽氣候變遷可能是因為數種機制作用在重要的海洋環流上而導致。這種環流譬如像是墨西哥灣流，它會將赤道溫暖的海水往北運輸至大西洋，在北大西洋海水會冷卻而下沉至冰層下的冰冷海底，並逐漸被推送回南邊。這種海水幫浦機制可能會因一些變動而弱化甚至停擺，像是淡水水壓、冰層崩解或是海冰移動，這會導致氣候變化幅度增加。

Natural and human-induced climate changes

自然與人為導致的氣候變遷

The climate during the warm interglacial periods is more stable than the climate of ice age climate.

在溫暖間冰期時的氣候較冰河氣的氣候要更加穩定。

"In fact, we see that the ice age climate is what we call 'multifractal', which is a characteristic that you see in very chaotic systems, while the interglacial climate is 'monofractal'. This means that the ratio between the extremes in the climate over different time periods behaves like the ratio between the more normal ratios of different timescales," explains Peter Ditlevsen

「事實上我們發現冰河期的氣候呈現出『多重碎形』(multifractal)，你可以在非常混亂的系統中發現這種特徵；而間冰期氣候則呈現『單一碎形』(monofractal)，這代表間冰期不同時段內極端氣候的比例，跟不同時間尺度下的正常比例之間更加相似。」Peter Ditlevsen解釋。

This new characteristic of the climate will make it easier for climate researchers to differentiate between natural and human-induced climate changes, because it can be expected that the human-induced climate changes will not behave in the same way as the natural fluctuations.

這項新發現的氣候特性可以讓氣候研究人員更輕易地分辨出自然與人為導致的氣候變遷，因為可以預期人類導致的氣候變遷的行為模式會跟自然波動之間有所差異。

"The differences we find between the two climate states also suggest that if we shift the system too much, we could enter a different system, which could lead to greater fluctuations. We have to go very far back into the geological history of the Earth to find a climate that is as warm as what we are heading towards. Even though we do not know the climate variations in detail so far back, we know that there were abrupt climate shifts in the warm climate back then," points out Peter Ditlevsen.

「我們發現的這兩個氣候狀態之間的差異也意味著如果這個系統被我們過度改變，我們就有可能進入一個截然不同的系統，而可能導致更大的變化發生。我們必須要探究地球地質史至十分久遠之處，才能找到與我們即將邁入的氣候同樣溫暖者。即便我們還不清楚那麼久以前氣候變化的細節，我們確實知道在過去的溫暖氣候下曾發生急劇的氣候變化。」 Peter Ditlevsen指出這點。

引用自：University of Copenhagen - Niels Bohr Institute. "Climate variations analyzed five million years back in time." ScienceDaily. ScienceDaily, 16 March 2016. 

地球早期也許十分寒冷

原始網址：www.sciencedaily.com/releases/2016/03/160317144620.htm

Early Earth may have been ice cold

地球早期也許十分寒冷

When Earth's first organisms were formed, it may have been in an ice cold ocean. New research, published in Science Advances, indicates that both land and ocean were much colder than previously believed.

地球最初的生命也許誕生在一座冰冷的海洋當中。刊登在《科學前緣》(Science Advances)的新研究指出，也許當時的陸地和海洋都較先前認為的要寒冷許多。

Many researchers believe that Earth's early oceans were very hot, reaching 80° Celsius, and that life originated in these conditions. New findings may prove the opposite to be true. Harald Furnes, Professor Emeritus at the Department of Earth Science, has analysed volcanic and sedimentary rocks in the Barberton Greenstone Belt, South Africa. The volcanic rocks were deposited at depths of 2 to 4 kilometres.

許多研究人員認為早期地球的海洋十分滾燙，溫度可達攝氏80度，而生命就在這種環境條件下誕生。新研究或許證明了相反的論述才是正確的。卑爾根大學地球科學系的榮譽教授 Harald Furnes分析了南非 Barberton綠岩帶的火山岩與沉積岩而得到了這項結論。這些火山岩的沉積深度為水深2至4公里處。

"We have found evidence that the climate 3.5 billion years ago was a cold environment," says Furnes.

「我們找到了証據指出35億年前的氣候環境十分寒冷。」 Furnes說。

Along with Professor Maarten de Wit from Nelson Mandela Metropolitan University, South Africa, Furnes has published the results in the journal Science Advances.

Furnes和納爾遜曼德拉都市大學的Maarten de Wit教授將他們的合作成果刊登於期刊《科學前緣》。

A cold globe

酷寒星球

The rocks analysed by Furnes and de Wit were formed at latitudes comparable with that of the Canary Islands. Some of the sedimentary rocks associated with the volcanic rocks, show a remarkable resemblance to those known from more recent ice ages.

Furnes和de Wit分析的岩石形成緯度位置大致與現今的加那利群島(北緯30度左右)相當。其中一些伴隨火山岩的沉積岩與在較為近代的冰河期形成的岩石之間有驚人的相似性。

"This may indicate that Earth, 3.5 billion years ago, experienced an extensive, perhaps global, ice age," Furnes says.

「這或許意味著35億年前冰河曾經十分廣布，甚至全球皆進入了冰河期。」 Furnes說。

Past ocean temperatures are measured by analysing the relations between oxygen isotopes in rocks known as "chert," a rock composed of pure silicium-oxide. These South African rocks have been exposed to high temperatures. Even so, this is related to hydrothermal activity, or springs of extremely hot water, pumped from the ocean bed.

分析一種幾乎由純矽氧化物組成的岩石，即一般所稱的「燧石」(chert)中氧同位素之間的關係，可以得知過去海洋的溫度。結果顯示這些南非的岩石曾經位處高溫環境。然而這跟從海床上湧出的熱泉活動，也就是溫泉或著極高溫的水有關。

Similar to present climate

與現在的氣候雷同

Additionally, the researchers found more proof indicating that these rocks had been exposed to cold water. By examining finely grained sedimentary rocks (originally a claylike mud), that exists along with the deep-submarine volcanic rocks, the researchers found gypsum. Gypsum is produced under high pressure and at very cold temperatures, as in the present deep ocean.

除此之外，研究人員發現了更多證據顯示這些岩石曾位處冷水當中。研究人員檢驗了跟深海火山岩並存的細顆粒沉積岩(原先為黏土狀的泥土)，發現其中有石膏。石膏生成於高壓低溫的環境中，譬如說現在的深海。

"In other words, we have found independant lines of evidence that the climate conditions at this time may have been quite similar to the conditions we have today," says Furnes.

「換言之，我們發現了數條獨立線索指出當時的氣候條件也許跟現在我們可見的環境十分相似。」 Furnes說。

Furnes thinks some researchers may have difficulties accepting the new knowledge of an early, cold Earth. A paradigm shift in Earth Science is not to be expected, but he thinks the climate of the early earth will be seen in a new light.

Furnes認為部分研究人員也許很難信服這個冰冷的早期地球的新學說。他並不期待這會撼動地球科學的基本理論，但他認為未來要用全新的觀點來看待地球早期的氣候。

"I think that this will force research to go further," he says.

「我想這會促使未來的研究去更加深入探討。」他說。

引用自：University of Bergen. "Early Earth may have been ice cold." ScienceDaily. ScienceDaily, 17 March 2016. 

 

來自陸地的碳在上次冰河期消退時具有重要地位

原文網址：www.sciencedaily.com/releases/2016/03/160314161245.htm

Carbon from land played a role during last deglaciation

來自陸地的碳在上次冰河期消退時具有重要地位

As the Earth emerged from its last ice age several thousand years ago, atmospheric carbon dioxide increased and further warmed the planet. Scientists have long speculated that the primary source of this CO2 was from the deep ocean around Antarctica, though it has been difficult to prove.

自地球於數萬年前進入末次冰河期起，大氣中的二氧化碳便不斷累積而進一步暖化地球。雖然相當難以證實，但科學家長期以來猜測這些二氧化碳的主要來源是南極周圍的深海。

A new study published this week in Proceedings of the National Academy of Sciences confirmed that the ocean played a significant role in the rise of atmospheric carbon dioxide, but also documents the signature of land-based carbon sources in Antarctic ice cores that contributed to abrupt increases in CO2.

刊登於本周《美國國家科學院學報》(Proceedings of the National Academy of Sciences, PNAS)的新研究證實海洋的確在大氣二氧化碳濃度的上升中具有重要地位，但同時也論述南極冰芯中的碳有來自陸地的跡象，顯示陸地在二氧化碳的突然上升中佔有一席之地。

"There wasn't a steady rate of rising carbon dioxide during the last deglaciation," said Edward Brook, an Oregon State University paleoclimatologist and co-author on the PNAS study. "It happened in fits and starts. With the new precise techniques we developed to fingerprint the sources, it is apparent that the early carbon largely came from the ocean, but we think the system got a jolt from an influx of land-based carbon a few times as the climate warmed."

「在末次冰消期( last deglaciation)時二氧化碳的上升速率並非固定。」此篇刊於PNAS的研究的共同作者，奧勒岡州立大學的古氣候學家 Edward Brook說。「這起事件發生地時快時慢。利用我們研發可以追查二氧化碳來源的精準新技術，結果顯示碳起初大都來自海洋，但我們認為隨著氣候逐漸變暖，這個系統會屢次受到來自陸地的碳影響而擺盪。」

The study was funded by the National Science Foundation with support from the Marsden Fund Council in New Zealand.

這起研究的資金來自國家科學基金會，並由紐西蘭的Marsden基金委員會提供協助。

The breakthrough came from the comparison of carbon isotope ratios in pristine samples of ice mined from the Taylor Glacier in Antarctica. Although such isotopic fingerprinting strategies have been attempted before, the key was detailed work both in the field and in the laboratory that improved the precision to read the record in fine detail.

這起突破性的研究來自於完整冰芯樣本中的碳同位素比對結果，其採自於南極的Taylor冰河。雖然早已有人試過這種同位素測蹤技術，但這起研究的關鍵是他們的野外和實驗室作業皆相當詳盡，使得他們的精確度更加提高而能夠徹頭徹尾地解讀這些紀錄。

The study found that during the initial rise in atmospheric CO2 -- from 17,600 years ago to 15,500 years ago -- the light isotope 12-C increased faster than the heavier isotopes, pointing to a release of carbon from the deep ocean. However, at about 16,300 years ago and 12,900 years ago, there were abrupt, century-scale perturbations in the carbon ratio that suggested rapid release of carbon from land sources such as plants and soils.

研究發現從17,600至15,500年前大氣二氧化碳濃度剛開始上升的階段，較輕的同位素碳-12上升得比較重的同位素還要快，顯示碳從深海中釋放了出來。然而在16,300和12,900年前，碳同位素卻突然有些長達數百年的擾動，代表來自陸地(像是植物和土壤)的碳在這段期間迅速排放至大氣。

Although the region of the CO2 source is not clear, the scientists say, at least one of the two events may come from the tropics because methane from tropical swamps rose at the same time.

科學家說雖然這些二氧化碳的來源地區尚未明朗，但這兩起事件的其中之一可能出自熱帶，因為同一時間來自熱帶沼澤的甲烷量也提升了。

"One theory," Brooks said, "is that an influx of icebergs in the Northern Hemisphere at about 16,300 years ago -- from retreating ice sheets -- cooled the North Atlantic Ocean and pushed the tropical rain belt southward over Brazil, expanding the wetlands. Swamps in the Southern Hemisphere, in places like Brazil, may have become wetter and produced methane, while plants and soils in the Northern Hemisphere, in places like China, may have been hit by drought and produced CO2."

「有項理論認為在16,300年前因為冰棚退縮使得北半球冰山流入海洋的速率增加，造成北大西洋冷卻，並將熱帶雨帶推至巴西以南，濕地因而擴展。位處南半球，比如巴西的沼澤地或許會因此變得更加潮濕而製造更多甲烷；而在北半球，像是中國的植物和土壤卻可能因遭受乾旱而產生二氧化碳。」

During the next 4,000 years, the continued rise of atmospheric CO2 -- by about 40 parts per million -- was marked by small changes in the carbon-13 to carbon-12 ratio indicating additional sources of carbon from rising ocean temperatures. This CO2 source, analogous to the bubbles released from warming soda pop, may have added to the biological carbon sources.

在接下來4000年大氣二氧化碳濃度持續攀升約10億分之4的過程中，碳-13與碳-12的比例有幾處些微的變化，顯示有額外來源的碳因為海洋溫度升高而出現。這些碳的來源可以比喻成碳酸飲料加熱後冒出的氣泡，它們也許會加入那些來自生物的碳。

The application of this carbon isotope technique became possible because of a unique site along the margin of the Antarctic ice sheet where old ice that flowed from the interior is exposed at the surface of a large glacier -- Taylor Glacier -- named for a geologist on an early expedition to the frozen continent. Ice that normally would be a mile or more below the surface is available to easily sample in large quantities.

這種碳同位素技術得以運用的原因在於樣品來自得天獨厚的環境。這些樣品的採集地點為一處南極冰棚的邊緣地帶，這是一條大型冰川-Taylor冰川(以一位早期遠征此冰封大陸的地質學家命名)中的古老冰塊從內部流出至表面處，因此正常來說要在冰河表面下一英哩甚至更深處才能取得的冰可以在此輕易地大量採樣。

These large samples, laboriously cut from the exposed ice layers, allowed the precise measurements, the Oregon State researchers report.

據奧勒岡州立大學的研究人員描述，他們可以精確分析這些從出露的冰層上辛勤切割下的大量樣品。

"The isotope ratio technique gives us a sort of 'return address' for carbon dioxide," noted Thomas Bauska, a former Ph.D. student and post-doctoral researcher in OSU's College of Earth, Ocean, and Atmospheric Sciences, who was lead author on the PNAS study. "The technique is new, extremely precise and gives us one of the best windows into the Earth's past climate."

「同位素技術提供給我們的資訊有點像是二氧化碳的『寄件地址』。」此篇刊登於PNAS的研究的第一作者 Thomas Bauska如此解釋。他之前是奧勒岡州立大學地球、海洋暨大氣科學系的博士生及博士後研究員。「這項技術不但新穎且極度精確，還給了我們窺向地球過去氣候的絕佳管道。」

Bauska is now a post-doctoral researcher at the University of Cambridge in England.

Bauska現在是英國劍橋大學的博士後研究員。

That window into the past may provide hints at what may happen in the future under a new global warming regime, noted Alan Mix, an Oregon State oceanographer and co-author on the study. However, he cautioned, it isn't always simple to predict the future based on past events.

此篇研究的共同作者，奧勒岡州立大學的海洋學家 Alan Mix點出這個管道也許可以提供我們在新的全球暖化局勢下，未來可能會發生何種事物的蛛絲馬跡。然而，他也提醒以過去的事件來預測未來並非總是那麼單純。

"The rise of CO2 is a complicated beast, with different behaviors triggered at different times," Mix said. "Although the natural changes at the end of the ice age are not a direct analogy for the future, the rapid changes do provide a cautionary tale. Humanmade warming from CO2 pollution may trigger further release from 'natural sources,' and this could exacerbate greenhouse gases and warming."

「二氧化碳的上升是個相當錯綜複雜的過程，不同的時間點可能會有截然不同的反應發生。」 Mix說。「雖然上次冰河期末的自然變化並不能直接類推至將來，但這些迅速變化確實可成為借鏡。排放二氧化碳造成的人為暖化可能會進一步造成其他『自然來源』隨之釋放溫室氣體，而增加其濃度並加劇暖化。」

Other authors on the PNAS study include Daniel Baggenstos and Jeffrey Severinghaus, Scripps Institution of Oceanography; Shaun Marcott, University of Wisconsin-Madison; Vasillii Petrenko, University of Rochester; Hinrich Schaefer, National Institute of Water and Atmospheric Research in New Zealand; and James Lee, Oregon State University.

此篇PNAS的研究的其他作者還有斯克里普斯海洋研究所的 Daniel Baggenstos和Jeffrey Severinghaus；威斯康辛大學麥迪遜分校的 Shaun Marcott；羅徹斯特大學的 Vasillii Petrenko；紐西蘭國家水資源與大氣研究院的 Hinrich Schaefer及奧勒岡州立大學的 James Lee。

引用自：Oregon State University. "Carbon from land played a role during last deglaciation." ScienceDaily. ScienceDaily, 14 March 2016. 

新研究顯示人類對氣候的影響可追溯至1930年代

原文網址：www.sciencedaily.com/releases/2016/03/160308134917.htm

Human influence on climate dates back to 1930s, new research finds

新研究顯示人類對氣候的影響可追溯至1930年代

Humans have triggered the last 16 record-breaking hot years experienced on Earth (up to 2014), with our impact on the global climate going as far back as 1937, a new study finds.

新研究顯示人類導致了地球最近16個氣溫創新高的年份(至2014年為止)，而我們對全球氣候的影響最遠可追溯至1937年。

The study suggests that without human-induced climate change, recent hot summers and years would not have occurred. The researchers also found that this effect has been masked until recently in many areas of the world by the wide use of industrial aerosols, which have a cooling effect on temperatures.

此篇研究認為若沒有人類導致的氣候變遷，就不會發生近年來的熾熱夏季及年份。研究人員也發現這類影響在世上許多處可能因工業氣膠廣泛使用所造成的冷卻效應而被暫時掩飾，直到近幾年才展露出來。

"Everywhere we look, the climate change signal for extreme heat events is becoming stronger," said Andrew King, a climate extremes research fellow at the University of Melbourne, Australia and lead author of the study. "Recent record-breaking hot years globally were so much outside natural variability that they were almost impossible without global warming."

「不管我們觀察何處，極端高熱事件是氣候變遷的表徵可說是越來越明顯。」 此篇研究的第一作者Andrew King說，他是澳洲墨爾本大學極端氣候中心的研究員。「最近幾年發生在全球各處的破紀錄高溫遠遠超出了自然變化，其程度之大若無全球暖化幾乎不可能發生。」

The researchers examined weather events that exceeded the range of natural variability and used climate modelling to compare those events to a world without human-induced greenhouse gases. The study was accepted for publication yesterday in Geophysical Research Letters, a journal of the American Geophysical Union.

研究人員檢視這些超出自然變化範圍的氣候事件，並將這些事件以氣候模型來跟沒有人類排放溫室氣體的世界互相比較。這篇研究於昨日被美國地球物理學會的期刊《地球物理通訊》接受並刊登。

According to the new study, record-breaking hot years attributable to climate change globally are 1937, 1940, 1941, 1943-44, 1980-1981, 1987-1988, 1990, 1995, 1997-98, 2010 and 2014.

根據此研究，因全球氣候變遷導致的破紀錄高溫年份分別為 1937、1940、 1941、1943-44、1980-1981、1987-1988、1990 、1995、1997-98、2010和2014年。(為什麼這邊算起來只有15個)

"In Australia, our research shows the last six record-breaking hot years and last three record-breaking hot summers were made more likely by the human influence on the climate," King said. "We were able to see climate change even more clearly in Australia because of its position in the Southern Hemisphere in the middle of the ocean, far away from the cooling influence of high concentrations of industrial aerosols."

「我們認為澳洲最近六個破紀錄的高溫年份和最近三個破紀錄的高溫夏季很可能是因為人類對氣候的影響而導致。」King說。「我們在澳洲可以更清楚地看到氣候變遷的影響，這是因為它位處南半球的海洋中央，距高濃度工業氣膠造成的冷卻效應距離甚遠。」

Aerosols in high concentrations reflect more heat into space, thereby cooling temperatures. However, when those aerosols are removed from the atmosphere, warming returns rapidly. The researchers observed this impact when they looked at five different regions: Central England, Central Europe, the central United States, East Asia and Australia.

高濃度的氣膠能反射更多的熱量回太空，因而可以降低氣溫。然而，一旦將這些氣膠從大氣中排除，氣溫就會迅速回暖。研究人員檢視了以下五個不同地區而觀察到上述效應：英格蘭中部、歐洲中部、美國中部、亞洲東部和澳洲。

There were cooling periods, likely caused by aerosols, in Central England, the central United States, Central Europe and East Asia during the 1970s before accelerated warming returned, and aerosol concentrations also delayed the emergence of a clear human-caused climate change signal in all regions studied except Australia, according to the study.

根據此篇研究，在1970年代英格蘭中部、歐洲中部、美國中部和東亞在暖化重回而加劇之前，都可能有因為氣膠而導致的冷化時期。另外，除了澳洲之外，其他所有地區都因為氣膠濃度較高，而造成人為導致的氣候變遷的明確跡象延後出現。

"In regards to a human-induced climate change signal, Australia was the canary in the coal mine for the rest of the world," King said.

「就人類導致的氣候變遷跡象而言，澳洲對世上其餘地區而言就像是煤礦坑裡的金絲雀。」King說。

引用自：American Geophysical Union. "Human influence on climate dates back to 1930s, new research finds." ScienceDaily. ScienceDaily, 8 March 2016. 

「遠古之根」：科學家辨認出已知最早的陸地居民化石

原文網址：www.sciencedaily.com/releases/2016/03/160302082245.htm

'A load of old rot': Fossil of oldest known land-dweller identified

「遠古之根」：科學家辨認出已知最早的陸地居民化石

A fossil dating from 440 million years ago is not only the oldest example of a fossilised fungus, but is also the oldest fossil of any land-dwelling organism yet found. The organism, and others like it, played a key role in laying the groundwork for more complex plants, and later animals, to exist on land by kick-starting the process of rot and soil formation, which is vital to all life on land.

這具4億4千萬年前的化石不只是現存樣品中最古老的真菌化石，同時也是迄今發現的陸居生物化石中年代最久遠者。這種生物和它的同類開啟了陸地上的生物腐朽及土壤形成作用，這對所有陸生生物來說都至關重要。因此在讓後世的高階植物及動物隨後得以在陸地安身立命的基礎建設上，它們扮演了關鍵性的一環。

This early pioneer, known as Tortotubus, displays a structure similar to one found in some modern fungi, which likely enabled it to store and transport nutrients through the process of decomposition. Although it cannot be said to be the first organism to have lived on land, it is the oldest fossil of a terrestrial organism yet found. The results are published in the Botanical Journal of the Linnean Society.

這種稱作Tortotubus的遠古拓荒者身上有一種構造跟某些現代真菌的十分相似，可能可以幫助它們在進行分解作用時儲存和運輸養分。雖然無法斷定它們就是在陸地上生活的第一種生物，但卻是目前為止所能找到的最古老陸生生物化石。這項研究結果刊登於《林奈學會植物學雜誌》(Botanical Journal of the Linnean Society)。

"During the period when this organism existed, life was almost entirely restricted to the oceans: nothing more complex than simple mossy and lichen-like plants had yet evolved on the land," said the paper's author Dr Martin Smith, who conducted the work while at the University of Cambridge's Department of Earth Sciences, and is now based at Durham University. "But before there could be flowering plants or trees, or the animals that depend on them, the processes of rot and soil formation needed to be established."

「在這種生物存活的年代，幾乎所有的生命都侷限在海洋當中。陸地上尚未演化出比簡單的苔癬和地衣類更複雜的生物。」本篇論文的作者 Martin Smith教授說。目前就職於杜倫大學的他於劍橋大學地球科學系任職時進行了此篇研究。「在開花植物和樹木，還有以它們維生的動物出現之前，(陸地上)必須要先建立起一套分解作用和土壤形成作用。」

Working with a range of tiny microfossils from Sweden and Scotland, each shorter than a human hair is wide, Smith attempted to reconstruct the method of growth for two different types of fossils that were first identified in the 1980s. These fossils had once been thought to represent parts of two different organisms, but by identifying other fossils with 'in-between' forms, Smith was able to show that the fossils actually represented parts of a single organism at different stages of growth. By reconstructing how the organism grew, he was able to show that the fossils represent mycelium -- the root-like filaments that fungi use to extract nutrients from soil.

Smith研究了一群來自瑞典和蘇格蘭的極端微小化石，當中的每一具寬度都比毛髮還要細小。他企圖重建兩種在1980年代首度辨認出來的化石的生長模式。過去一度認為這兩種化石分屬於兩種不同生物的結構，但在辨識出一些跟兩者皆頗為相似的其他化石後，Smith得以下結論說這些化石其實是同一生物在不同生長階段的身體部位。在重建了這種生物的生長模式後，他認為這些化石代表了菌絲，一種真菌用來從土壤中吸收養分的根狀纖毛構造。

It's difficult to pinpoint exactly when life first migrated from the seas to the land, since useful features in the fossil record that could help identify the earliest land colonisers are rare, but it is generally agreed that the transition started early in the Palaeozoic era, between 500 and 450 million years ago. But before any complex forms of life could live on land, there needed to be nutrients there to support them. Fungi played a key role in the move to land, since by kick-starting the rotting process, a layer of fertile soil could eventually be built up, enabling plants with root systems to establish themselves, which in turn could support animal life.

由於化石紀錄中可以用來辨認出最早移居至陸地的生物為何者的證據相當稀少，因此很難精確指出生命首度從海洋遷往陸地的時間點。但學者一般認同在古生代早期生命開始往陸地邁進，約在5億至4億5000萬年前。而在任何複雜的生命形式能在陸地生活之前，陸上必須要先有養分才能夠餵養它們。在爬上陸地的過程當中，真菌扮演了關鍵腳色，這是因為它們能使分解作用開始運作，最終可以形成一層肥沃的土壤。具備根系的植物得以依此落腳維生，連帶使動物能夠生長。

Fungi play a vital role in the nitrogen cycle, in which nitrates in the soil are taken up by plant roots and passed along food chain into animals. Decomposing fungi convert nitrogen-containing compounds in plant and animal waste and remains back into nitrates, which are incorporated into the soil and can again be taken up by plants. These early fungi started the process by getting nitrogen and oxygen into the soil.

真菌在氮循環中為不可或缺的一環。在此循環當中，土壤裡的硝酸鹽會被植物根部汲取，並隨著食物鏈轉移至動物身上。能行使分解作用的真菌會將含氮的動植物排泄物和遺骸轉化回硝酸鹽，當它們重新回到土壤後便能再次被植物利用。這些早期的真菌藉由將獲取土壤中的氮和氧而開啟了這整個過程。

Smith found that Tortotubus had a cord-like structure, similar to that of some modern fungi, in which the main filament sends out primary and secondary branches that stick back onto the main filament, eventually enveloping it. This cord-like structure is often seen in land-based organisms, allowing them to spread out and colonise surfaces. In modern fungi, the structure is associated with the decomposition of matter, allowing a fungus colony to move nutrients to where they are needed -- a useful adaptation in an environment where nutrients are scarce and unevenly distributed.

Smith發現 Tortotubus具有跟某些現代真菌相當類似的繩索狀構造。這是種由主菌絲發散出的分支及更細的分支回貼在主菌絲身上，最終將其層層包覆而形成的構造。這種繩索狀構造通常見於陸生生物，這有助於它們附著在固體表面並往外擴散。在現生的真菌身上，此構造通常跟物質的分解有關。真菌菌落可以利用它們將養分移送至有需求的部分，這在營養稀少且不均勻分布的環境中是種相當實用的適應構造。

In contrast with early plants, which lacked roots and therefore had limited interaction with activity beneath the surface, fungi played an important role in stabilising sediment, encouraging weathering and forming soils.

原始植物由於缺少根部，因此它們難以跟地表之下的環境有所互動；相較起來，真菌在穩定環境、促進風化作用和形成土壤的過程中，皆具有更加重要的地位。

"What we see in this fossil is complex fungal 'behaviour' in some of the earliest terrestrial ecosystems -- contributing to soil formation and kick-starting the process of rotting on land," said Smith. A question, however, is what was there for Tortotubus to decompose. According to Smith, it's likely that there were bacteria or algae on land during this period, but these organisms are rarely found as fossils.

「我們從這些化石中看到在某些最原始的陸地生態系系統中，已經有相當複雜的真菌作用在進行著。它們的貢獻使土壤形成，並開啟了陸上的分解作用。」 Smith說。然而，有個問題是： Tortotubus究竟在陸地上分解著什麼物質。據 Smith說，在那段時期陸上可能已經有細菌或藻類存活，但這些生物很難以化石的形式發現。

Additionally, the pattern of growth in Tortotubus echoes that of the mushroom-forming fungi, although unambiguous evidence of mushrooms has yet to be found in the Palaeozoic fossil record. "This fossil provides a hint that mushroom-forming fungi may have colonised the land before the first animals left the oceans," said Smith. "It fills an important gap in the evolution of life on land."

此外，Tortotubus的生長模式也反映出當時可能已有會形成蕈菇的真菌了，雖然迄今我們仍尚未在古生代化石紀錄中確切發現蕈菇存在的證據。「這些化石暗示著會形成蕈菇的真菌定居在陸地的時間，也許比第一隻動物離開海洋還要來得早。」 Smith說。「這填補了陸地生命演化史上的一大空缺。」

The research was supported by Clare College, Cambridge.

本研究由劍橋大學克萊爾學院贊助。

引用自：University of Cambridge. "'A load of old rot': Fossil of oldest known land-dweller identified." ScienceDaily. ScienceDaily, 2 March 2016.