全球變暖，比我們預(yù)想的更嚴(yán)重

A new study based on evidence from past warm periods suggests global warming may be double what is forecast.

人們發(fā)現(xiàn)，全球變暖的規(guī)模可能是之前預(yù)測值的兩倍，這個(gè)結(jié)論是基于過去對溫暖期的研究得出的。
 

Future global warming may eventually be twice as warm as projected by climate models and sea levels may rise six metres or more even if the world meets the 2°C target, according to an international team of researchers from 17 countries.

一個(gè)由17個(gè)國家的研究人員組成的研究小組稱，即使世界實(shí)現(xiàn)了“2攝氏度”目標(biāo)，全球變暖可能是預(yù)測模型的兩倍，海平面也會上升不止六米。(“2攝氏度閾值”說是歐盟率先提出來的。其內(nèi)容是，相對于1750年工業(yè)化前的水平，全球平均氣溫升高2攝氏度是人類社會可以容忍的最高升溫，并由此引發(fā)出，為確保到本世紀(jì)末全球升溫不超過這個(gè)閾值，則全球在2050年以前必須將溫室氣體排放在1990年的基礎(chǔ)上至少減少50%，即所謂全球排放減半。)

The findings published last week in Nature Geoscience are based on observational evidence from three warm periods over the past 3.5 million years when the world was 0.5°C-2°C warmer than the pre-industrial temperatures of the 19th Century.

這項(xiàng)研究已經(jīng)發(fā)布在上周的《Nature Geoscience》上：據(jù)過去350萬年的三個(gè)溫暖期的觀測證據(jù)，這幾個(gè)時(shí)期的世界溫度比19世紀(jì)前工業(yè)化時(shí)期水平高0.5-2攝氏度不等。

The research also revealed how large areas of the polar ice caps could collapse and significant changes to ecosystems could see the Sahara Desert become green and the edges of tropical forests turn into fire dominated savanna.

該研究還表明，極地冰蓋可能會大面積崩潰，生態(tài)系統(tǒng)的重大變化可能會讓撒哈拉沙漠變成綠洲，而熱帶森林的邊緣之處也成了稀樹草原。(稀樹草原是炎熱、季節(jié)性干旱氣候條件下長成的植被類型，其特點(diǎn)是底層連續(xù)高大禾草之上有開放的樹冠層，即稀疏的喬木。世界最大片的稀樹草原見于非洲、南美洲、澳大利亞、印度、緬甸 -泰國地區(qū)和馬達(dá)加斯加。)

"Observations of past warming periods suggest that a number of amplifying mechanisms, which are poorly represented in climate models, increase long-term warming beyond climate model projections," said lead author, Prof Hubertus Fischer of the University of Bern."This suggests the carbon budget to avoid 2°C of global warming may be far smaller than estimated, leaving very little margin for error to meet the Paris targets."

來自伯恩大學(xué)的第一作者休伯特斯 · 費(fèi)希爾教授說：“對過去變暖期的觀察表明，氣候模型中代表性較差的一些放大機(jī)制，揭示了我們可能會經(jīng)歷長時(shí)間的溫暖期，這在當(dāng)初天氣模型的預(yù)測之外。而這就意味著，因?yàn)橹肮烙?jì)錯誤，所以2攝氏度目標(biāo)難以實(shí)現(xiàn)，而《巴黎協(xié)定》的誤差就得另當(dāng)別論了。”

To get their results, the researchers looked at three of the best-documented warm periods, the Holocene thermal maximum (5000-9000 years ago), the last interglacial (129,000-116,000 years ago) and the mid-Pliocene warm period (3.3-3 million years ago).

為了得出結(jié)論，研究人員觀察了三個(gè)記錄最佳的溫暖期，分別是全新世(5000 - 9000年前)、最后一次間冰期(129000 - 116000年前)和上新世中期暖期(330- 300)萬年前。

The warming of the first two periods was caused by predictable changes in the Earth's orbit, while the mid-Pliocene event was the result of atmospheric carbon dioxide concentrations that were 350-450ppm – much the same as today.

前兩個(gè)時(shí)期的變暖是由地球軌道變化引起的，這在我們的預(yù)料之中，而上新世中期變暖則是因?yàn)榇髿庵卸趸紳舛纫呀?jīng)達(dá)到了350-450ppm。

Combining a wide range of measurements from ice cores, sediment layers, fossil records, dating using atomic isotopes and a host of other established paleoclimate methods, the researchers pieced together the impact of these climatic changes.In combination, these periods give strong evidence of how a warmer Earth would appear once the climate had stabilized. By contrast, today our planet is warming much faster than any of these periods as human caused carbon dioxide emissions continue to grow. Even if our emissions stopped today, it would take centuries to millennia to reach equilibrium.

研究人員對冰芯、沉積物層、化石記錄進(jìn)行了研究，利用原子同位素測量和大量其他的測量方式，并對結(jié)果進(jìn)行了綜合性考量，最后得出：這些時(shí)期已經(jīng)足以說明，一旦氣候穩(wěn)定下來，地球?qū)兊煤?ldquo;溫暖”。 相比之下，今天的地球的變暖速度比以上任何一個(gè)時(shí)期都快，因?yàn)槎趸寂欧帕咳栽诔掷m(xù)增長。 即使我們在今天就停止排放，地球也需要幾個(gè)世紀(jì)甚至是幾千年才能達(dá)到平衡。

The changes to the Earth under these past conditions were profound – there were substantial retreats of the Antarctic and Greenland ice sheets and as a consequence sea-levels rose by at least six metres; marine plankton ranges shifted reorganising entire marine ecosystems; the Sahara became greener and forest species shifted 200 km towards the poles, as did tundra; high altitude species declined, temperate tropical forests were reduced and in Mediterranean areas fire-maintained vegetation dominated.

過去，地球發(fā)生了一系列的重大變化——南極和格陵蘭冰原大量退縮，因此海平面至少上升了6米; 海洋浮游生物使得整個(gè)海洋生態(tài)系統(tǒng)重組; 撒哈拉綠色區(qū)域更多了，森林物種向兩極移動200公里，苔原也不例外; 高海拔物種減少，溫帶熱帶森林減少，地中海地區(qū)也是以可燒林火的植被為主。

"Even with just 2°C of warming – and potentially just 1.5°C – significant impacts on the Earth system are profound," said co-author Prof Alan Mix of Oregon State University. "We can expect that sea-level rise could become unstoppable for millennia, impacting much of the world's population, infrastructure and economic activity."

俄勒岡州立大學(xué)的艾倫 · 米克斯教授是論文的合著者，她說:”不說2攝氏度，哪怕只有1.5攝氏度，對地球的影響也是巨大的?？梢韵胍姡谖磥淼那曛畠?nèi)，我們都無法阻止海平面上升，這對世界的人口、基層建筑、經(jīng)濟(jì)活動都有影響。”

Yet these significant observed changes are generally underestimated in climate model projections that focus on the near term. Compared to these past observations, climate models appear to underestimate long term warming and the amplification of warmth in Polar Regions.

然而，在氣候模型預(yù)測中，我們通常低估了這些重大的觀測變化，因?yàn)橹暗念A(yù)測往往集中短期時(shí)間內(nèi)的變化。與過去的觀測結(jié)果相比，氣候模型似乎低估了長期變暖效應(yīng)，也忽視了極地地區(qū)的升溫。

"Climate models appear to be trustworthy for small changes, such as for low emission scenarios over short periods, say over the next few decades out to 2100. But as the change gets larger or more persistent, either because of higher emissions, for example a business-as-usual-scenario, or because we are interested in the long term response of a low emission scenario, it appears they underestimate climate change," said co-author Prof Katrin Meissner, Director of the University of New South Wales Climate Change Research Centre."This research is a powerful call to act. It tells us that if today's leaders don't urgently address our emissions, global warming will bring profound changes to our planet and way of life – not just for this century but well beyond."

合著者新南威爾士大學(xué)氣候變化研究中心主任、卡特琳·邁斯納教授說：“氣候預(yù)測模型在預(yù)測小型變化時(shí)，還是可信的，比如短期內(nèi)(類似于從現(xiàn)在起到2100年)的低排放。不論是因?yàn)樘寂欧帕砍掷m(xù)增加，還是因?yàn)楝F(xiàn)在固有的商業(yè)模式，我們都低估了長遠(yuǎn)影響。而現(xiàn)在，這項(xiàng)研究就是一個(gè)強(qiáng)有力的號召。它告訴我們，如果今天不迫切地解決排放問題，全球變暖將給我們生存之地以及生活方式帶來重大變化，而且這種變化也不僅僅只影響我們這一個(gè)世紀(jì)。”