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Which Came First: Low CO2 or an Ice Age?
二氧化碳含量變低和冰河世紀(jì)哪個(gè)先來？
What starts an Ice Age? Clues exist in the remains of coccolithophores, a type of marine algae with a shell.
冰河世紀(jì)開始的原因是什么？線索在顆石藻化石中，顆石藻是一種帶殼的海洋藻類。
A study finds that some seven million years ago, the algae had to adapt to low levels of carbon dioxide in the atmosphere. They pulled CO2 from the surrounding seas for photosynthesis as well as bicarbonate—commonly known as baking soda. The study is in the journal Nature.
一份研究發(fā)現(xiàn)大約700萬年前，顆石藻必須適應(yīng)大氣中的低二氧化碳含量。他們從從周圍的海洋中和碳酸氫鹽中吸收二氧化碳用于光合作用。碳酸氫鹽俗稱小蘇打。這份研究發(fā)表在《自然》雜志上。
At that same time, sea surface temperatures were dropping, plants that were more efficient at using CO2 came to predominate on land and vast glaciers began to expand on the continents—an Ice Age was underway. The low concentrations of greenhouse gases in the atmosphere were thus linked to the era’s cool climate.
同時(shí)，海洋表面溫度也在下降，二氧化碳利用效率更高的植物得以主導(dǎo)大陸，大量的冰河開始在陸地上擴(kuò)張，冰河世紀(jì)即將來臨。溫室氣體二氧化碳在大氣中的低含量也就跟冰河世紀(jì)的冰冷氣候扯上了關(guān)系。
That situation is now reversed thanks mostly to fossil fuel burning. And the change is happening at least 30,000 times faster this time. In May, atmospheric concentrations of CO2 touched 400 parts-per-million for the first time in human existence. When they touch 500 ppm, the algae might no longer need the bicarbonate trick.
冰河世紀(jì)結(jié)束了，主要是由于化石燃料的燃燒。這次氣候改變速度比以前快至少30000倍。五月，在人類存在時(shí)期，二氧化碳大氣中含量首次變成0.04%。當(dāng)二氧化碳含量變成0.05%的時(shí)候，海藻可能不再需要小蘇打了。
—David Biello
