回到上新世？氣候變化或讓南極洲變“綠洲”

科學家警告，如果再不採取行動，南極洲的皚皚白雪將被綠色植被所取代。上一次出現“南極綠洲”是在300萬年前的上新世時期。如果人類還是無動於衷，那麼到2100年，地球將回歸恐龍時代的狀態。

Man-made climate change could turn Antarctica green, with plants colonising the land as ice sheets shrink, scientists have warned.

科學家警告說，人爲的氣候變化可能會讓南極洲“變綠”，隨着冰川消退，南極洲大陸上將會被植被覆蓋。

Experts believe clues about the future of the planet can be gleaned from the Pliocene period three million years ago, the last time carbon dioxide levels in the atmosphere were as high as they are today.

專家認爲，地球未來演變的趨勢可以從300萬年前的上新世時期找到線索，當時地球大氣中的二氧化碳水平和現在一樣高。

glean[ɡlin]: v. 收集

Carbon dioxide levels in the atmosphere reached 400 parts per million (ppm) on average in 2015 for the first time since records began, World Meteorological Organisation figures show.

世界氣象組織的數據顯示，2015年大氣中的二氧化碳平均水平達到了百萬分之400，是有記錄以來的最高水平。

There is likely to be a “lag” before the true effects of reaching such a threshold are felt, Professor Martin Siegert, co-director of the Grantham Institute at Imperial College said.

帝國理工學院格蘭瑟姆研究所的聯合主任馬丁·西格特說，人們對達到這樣一個臨界點的真實後果的感知會有一個“滯後期”。

However, he added, looking to the Pliocene era could offer clues as to how humans might deal with the challenges this creates.

但是，他補充說，人類要如何應對二氧化碳水平過高帶來的挑戰，可以從上新世時期找到線索。

During this period, sea levels were around 15 metres higher and temperature estimated to be between 2C and 3.5C warmer than now.

在這一時期，海平面上升了約15米，溫度比現在高出2到3.5攝氏度。

"[If] you put your oven on at home, and set it to 200C, the temperature doesn’t get to that immediately,” Prof Siegert said. “It takes a bit of time, and it's the same with the climate.”

西格特教授說：“如果你在家裏打開爐子，把溫度調到200度，不會立刻達到這一溫度。這需要一段時間，氣候也是一樣。”

Professor Dame Jane Francis, director of the British Antarctic Survey, said remnants of the forests of Antarctica have been found, which are probably dated to the Pliocene age.

英國南極觀測站的站長德蒙·簡·弗朗西斯教授說，南極洲森林的遺蹟已經被找到，這些森林很可能來自上新世時期。

"The really important significance of this is that we've got 400 ppm now, and if we had 400 ppm in the past, this is maybe where we are going back to,” she said. “Which is the ice sheets are going to shrink at times, not all the time but at times... which may allow plants to colonise in Antarctic land again.”

她說：“這些森林遺蹟之所以非常重要，是因爲我們現在的二氧化碳水平已經達到百萬分之400，如果過去地球的二氧化碳水平也曾經達到百萬分之400，這也許就是地球將回歸的狀態。冰川時不時地會消退，不是一直消退而是偶爾消退，這可能會讓植被重新覆蓋南極洲大陸。”

Before the industrial revolution in 1850 carbon dioxide levels were about 280 ppm and since then the temperature has increased globally by around 1C, Prof Siegert added.

西格特教授補充說，在1850年工業革命之前，二氧化碳水平約爲百萬分之280，自那以後全球溫度上升了約1攝氏度。

"What it means is that by the end of this century, we might expect another 1C,” he said.

他說：“這意味着到本世紀末，全球溫度將再上升1攝氏度。”

If carbon dioxide emissions continue at current rates, levels could soar to 1000 ppm by 2100, he added.

他還說，如果二氧化碳排放量以目前速度持續下去，到2100年，大氣中的二氧化碳水平將高達百萬分之1000。

This is the same as estimated levels around 100 million years ago, when dinosaurs roamed the earth and Antarctica was warmer and much greener.

屆時二氧化碳水平將和1億年前持平，那時候的地球恐龍橫行，南極洲比現在更溫暖，也綠得多。

He called for global action to reduce the amount of carbon dioxide in the atmosphere.

西格特教授呼籲全球採取行動來降低大氣中的二氧化碳水平。

"The consequences of what we have done over 150 years will continue into the future, so it's up to us to do something,” Prof Siegert said. “We will be judged in history on how well we respond to this issue, and at the moment we're not doing a very good job.”

西格特教授說：“過去150多年來人類的所作所爲造成的後果將會在未來持續發酵，我們有責任做些事情來防止全球變暖。後人會評判我們對氣候變化問題的應對方式，而眼下我們做的並不好。”