在地球磁場的維持上月球也許具有關鍵地位

原始網址：www.sciencedaily.com/releases/2016/04/160401075118.htm

The Moon may play a major role in maintaining Earth's magnetic field

在地球磁場的維持上月球也許具有關鍵地位

The Earth's magnetic field permanently protects us from the charged particles and radiation that originate in the Sun. This shield is produced by the geodynamo, the rapid motion of huge quantities of liquid iron alloy in the Earth's outer core. To maintain this magnetic field until the present day, the classical model required the Earth's core to have cooled by around 3,000 °C over the past 4.3 billion years. Now, a team of researchers from CNRS and Université Blaise Pascal[1] suggests that, on the contrary, its temperature has fallen by only 300 °C. The action of the Moon, overlooked until now, is thought to have compensated for this difference and kept the geodynamo active. Their work is published on 30 march 2016 in the journal Earth and Planetary Science Letters.

地球磁場長久以來保護我們免受來自太陽的帶電粒子和輻射所造成的傷害。這道屏障是由「地球發電機」(geodynamo)產生，此效應是因地球外核中的巨量液態鐵合金迅速流動而造成的。傳統模型認為要讓地球磁場維持至今日，地核必須在43億年的歲月中降溫將近3000°C。相反地，法國國家科學研究中心和克萊蒙費朗第二大學的研究人員近日提出的學說認為，地核溫度僅需降溫300°C就能維持地球磁場。他們認為彌補這個溫度差以及維繫地球發電機運作的關鍵因素是直到現在才被注意到的月球運動。這項研究刊登於2016年3月30日的《地球與行星科學通訊》期刊。

The classical model of the formation of Earth's magnetic field raised a major paradox. For the geodynamo to work, the Earth would have had to be totally molten four billion years ago, and its core would have had to slowly cool from around 6800 °C at that time to 3800 °C today. However, recent modeling of the early evolution of the internal temperature of the planet, together with geochemical studies of the composition of the oldest carbonatites and basalts, do not support such cooling. With such high temperatures being ruled out, the researchers propose another source of energy in their study.

傳統模型在解釋地球磁場如何形成時具有一個重大的矛盾。若要讓地球發電機運轉，地球在四十億年前必須要處於完全熔融的狀態，在這之後地核得從將近6800°C的高溫緩緩降溫至現今的 3800 °C。然而，最近模擬早期地球內部溫度如何演變的結果，以及對最古老的碳酸岩(carbonatite)和玄武岩成分進行的地球化學研究，皆不支持這樣的冷卻過程。由於上述結果排除掉如此高溫為可能的能量來源，所以這些研究人員在他們的研究之中提出了另外一種來源。

The Earth has a slightly flattened shape and rotates about an inclined axis that wobbles around the poles. Its mantle deforms elastically due to tidal effects caused by the Moon. The researchers show that this effect could continuously stimulate the motion of the liquid iron alloy making up the outer core, and in return generate Earth's magnetic field. The Earth continuously receives 3,700 billion watts of power through the transfer of the gravitational and rotational energy of the Earth-Moon-Sun system, and over 1,000 billion watts is thought to be available to bring about this type of motion in the outer core. This energy is enough to generate the Earth's magnetic field, which together with the Moon, resolves the major paradox in the classical theory. The effect of gravitational forces on a planet's magnetic field has already been well documented for two of Jupiter's moons, Io and Europa, and for a number of exoplanets.

地球的外型略呈扁平且以一根傾斜的轉軸為軸心自轉，而這根自轉軸本身也會繞著一個圓圈晃動；另外，地函內部也會發生塑性變形。以上的作用或多或少都跟月球造成的潮汐力有關。研究人員顯示這個作用力同樣也能促使組成外核的液態鐵合金不斷運動，進而產生地球磁場。在地球-月球-太陽系統中，重力和彼此繞行時產生的能量會持續轉換至地球身上，功率高達3兆7000億瓦。研究人員相信這些能量當中有超過1兆瓦被用來驅動外核中的這類運動，而如此龐大的能量足以產生地球磁場。因此將月球這項因子考量在內，便能夠解決傳統理論中的重大矛盾。在木星的兩顆衛星，木衛一「埃歐」及木衛二「歐羅巴」，還有一些地外行星上已經詳細記錄到這種重力對星球磁場的影響。

Since neither the Earth's rotation around its axis, nor the direction of its axis, nor the Moon's orbit are perfectly regular, their combined effect on motion in the core is unstable and can cause fluctuations in the geodynamo. This process could account for certain heat pulses in the outer core and at its boundary with the Earth's mantle.

既然地球自轉、地軸指向以及月球軌道這三者都並非是照著完美的規律運作，它們聯合起來對地核流動造成的效應就不會是穩定的，因此會造成地球發電機內部發生擾動。這可以用來解釋外核內部以及核幔邊界處發生的部分熱能高漲現象。

Over the course of time, this may have led to peaks in deep mantle melting and possibly to major volcanic events at the Earth's surface. This new model shows that the Moon's effect on the Earth goes well beyond merely causing tides.

長久下來，這種現象可能使深部地函的頂部熔融，並在地球表面造成重大的火山噴發事件。這個新模型顯示月球對地球造成的影響之大可不僅只有潮汐而已。

[1] At the Laboratoire Magmas et Volcans (CNRS/IRD/Université Blaise Pascal), part of the Observatoire de Physique du Globe de Clermont-Ferrand, the Institut de Recherche sur les Phénomènes Hors-équilibre (CNRS/Aix-Marseille Université/Ecole Centrale Marseille) and the Institut de Recherche en Astrophysique et Planétologie (CNRS/Université Toulouse III -- Paul Sabatier).

來源自：CNRS. "The Moon may play a major role in maintaining Earth's magnetic field." ScienceDaily. ScienceDaily, 1 April 2016.  

印尼的「哈比人」也許比之前認為的還要早滅絕

原文網址：www.sciencedaily.com/releases/2016/03/160330135304.htm

Indonesian 'Hobbits' may have died out sooner than thought

印尼的「哈比人」也許比之前認為的還要早滅絕

An ancient species of pint-sized humans discovered in the tropics of Indonesia may have met their demise earlier than once believed, according to an international team of scientists who reinvestigated the original finding.

根據一個國際科學家團隊重新調查的結果，於熱帶印尼發現的一種矮小的古代人種，他們比當初發現時認為的還要早迎接滅亡。

Published in the journal Nature this week, the group challenges reports that these inhabitants of remote Flores island co-existed with modern humans for tens of thousands of years.

之前發表的論文認為這些住在遠離塵囂的佛羅勒斯島上的居民，曾經跟現代人共同生活了數萬年之久。但本周刊登於《自然》(Nature)期刊上的論文則對此說法提出了質疑。

They found that the youngest age for Homo floresiensis, dubbed the 'Hobbit', is around 50,000 years ago not between 13,000 and 11,000 years as initially claimed.

他們發現這些暱稱為「哈比人」的佛羅勒斯人(Homo floresiensis)年代最近的骨骸為距今50,000年前，而非原先聲稱的距今11,000年前。

Led by Indonesian scientists and involving researchers from Griffith University's Research Centre of Human Evolution (RCHE) the team found problems with prior dating efforts at the cave site, Liang Bua.

這個團隊由印尼的科學家領導，並且有格里菲斯大學人類演化中心(RCHE)的研究人員參與其中。他們發現之前對這些骨骸出土的洞穴場址-梁布亞(Liang Bua)進行的定年方法有些問題。

"In fact, Homo floresiensis seems to have disappeared soon after our species reached Flores, suggesting it was us who drove them to extinction," says Associate Professor Maxime Aubert, a geochronologist and archaeologist at RCHE, who with RCHE's Director Professor Rainer measured the amount of uranium and thorium inside Homo floresiensis fossils to test their age.

「事實上，佛羅勒斯人似乎在我們所屬的物種到達佛羅勒斯島不久後就消失了。這意味著他們的滅亡是由我們促成的。」 RCHE的地質定年學家及考古學家 Maxime Aubert副教授說。他跟RCHE的計畫主持人， Rainer教授測量了佛羅勒斯人化石中的鈾和釷含量，以測得他們的生存年代。

"The science is unequivocal,'' Aubert said.

「這些科學證據可說無庸置疑。」Aubert說。

"The youngest Hobbit skeletal remains occur at 60,000 years ago but evidence for their simple stone tools continues until 50,000 years ago. After this there are no more traces of these humans."

「年代最近的哈比人化石大約是距今60,000年前，而他們遺留下來的粗糙石器則證明了他們直到55,000年前仍生活於此。然而在這之後就再也沒有這些人類生存於此的蛛絲馬跡了。」

While excavating at the limestone cave of Liang Bua in 2003, archaeologists found bones from diminutive humans unlike any people alive today. The researchers concluded the tiny cave dwellers evolved from an older branch of the human family that had been marooned on Flores for at least a million years. It was thought that this previously unknown population lived on Flores until about 12,000 years ago.

考古學家於2003年挖掘了位於梁布亞的石灰岩洞穴，並發現這些跟現今生存的人們截然不同的矮小人類骨骸。研究人員得出的結論認為這些矮小的穴居人是從人屬中古老的一支演化而來，他們漂流並孤立在佛羅勒斯島上至少已有100萬年的歷史。過去認為這群前所未見的人種至少在距今12,000年前都還生活在佛羅勒斯島上。

But the site is large and complex and the original excavators dug only a tiny portion of it. Years of further excavation has led to a much clearer understanding of the order of archaeological layers. It is now evident that when the original team collected samples for dating the main layer containing Hobbit bones they mistakenly took them from an overlying layer that is similar in composition, but far younger.

然而，最初開挖工作挖掘的只不過是這個巨大且複雜的遺址的一部分而已。經過數年的後續開挖工作後，研究人員更加瞭解了這些考古地層的年代先後順序。現在他們確知原先的團隊在定年含有哈比人化石的主要岩層時，他們誤從上覆的岩層採集樣品，雖然成分相似，然而年代卻年輕了許多。

"This problem has now been resolved and the newly published dates provide a more reliable estimate of the antiquity of this species,'' Aubert said.

「我們現在已經解決了這項問題。在新發表的論文中，我們提供了對這個物種的年代更可信的預估結果。」

But the mystery of what happened to these creatures remains.

然而，這個物種遭遇的一切仍然是個懸而未解的謎團。

RCHE archaeologist Dr Adam Brumm, who also participated in the study, said Hobbits are likely to have inhabited other Flores caves which may yield more recent signs of their existence. He believes Homo floresiensis probably suffered the same fate that befell Europe's Neanderthals -- our species simply out-competed and replaced them within a few thousand years.

同樣參與了此研究的RCHE考古學家，Adam Brumm教授說哈比人很可能也曾在佛羅勒斯島上的其他洞穴居住過，而我們或許能從中取得他們生活過的證據，且比先前的年代還要更近。他相信佛羅勒斯人遭受的厄運跟降臨在歐洲尼安德塔人身上的相同-我們這個物種在幾千內便淘汰並徹底取代了他們。

"They might have retreated to more remote parts of Flores, but it's a small place and they couldn't have avoided our species for long. I think their days were numbered the moment we set foot on the island."

「他們相當有可能撤離到佛羅勒斯島上更加隱密之處，但那蕞爾之地並不足以讓他們逃離我們這個物種的威脅太久。我想當我們登上這座島嶼的那一刻開始，他們的喪鐘就已經響起了。」

引用自：Griffith University. "Indonesian 'Hobbits' may have died out sooner than thought." ScienceDaily. ScienceDaily, 30 March 2016. 

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.