這樣的地球，我們從未生活過

在人類歷史上，我們從未在這樣的大氣中生活過

We humans have officially entered uncharted territory. In the roughly 2.5 million years our kind has walked the Earth, never before have we endured such an atmosphere.

我們?nèi)祟愓竭M入了未知領(lǐng)域。在人類在地球上行走的250萬年里，我們從未經(jīng)歷過這樣的大氣層。

New research on ancient soil has now confirmed that carbon dioxide levels in the past sixty years are the highest we've experienced in all of human history.

對古代土壤的最新研究已經(jīng)證實，過去60年的二氧化碳水平是人類歷史上最高的。

Throughout the entire Pleistocene era - which started 2,580,000 years ago - the authors found concentrations of CO2 were, on average, roughly 250 parts per million.

在整個更新世時期——25.8萬年前開始——作者發(fā)現(xiàn)二氧化碳的濃度平均約為百萬分之250。

Yet in the past sixty years or so, that consistency has appeared to rapidly unravel. Today, the findings suggest, our planet has reached 415 ppm for the first time in 2.5 million years.

然而，在過去60年左右的時間里，這種一致性似乎迅速瓦解。今天，研究結(jié)果表明，我們的星球在250萬年來首次達到了415 ppm。

"According to this research, from the first Homo erectus, which is currently dated to 2.1 to 1.8 million years ago, until 1965, we have lived in a low-carbon dioxide environment - concentrations were less than 320 parts per million," explains geoscientist Yige Zhang from Texas A&M University.

德州農(nóng)工大學(xué)的地球科學(xué)家張一格解釋說：“根據(jù)這項研究，從第一批直立人到1965年，我們生活在一個低二氧化碳的環(huán)境中——濃度低于百萬分之320。”

"So this current high-carbon dioxide environment is not only an experiment for the climate and the environment - it's also an experiment for us, for ourselves."

“因此，目前的高二氧化碳環(huán)境不僅是對氣候和環(huán)境的試驗，也是對我們自己的考驗。”

To figure out where we are going, first requires us to know where we've been. Studying past climates, Zhang says, can help provide some of that perspective and hopefully help us navigate our uncertain future.

要想知道我們要去哪里，首先需要知道我們?nèi)ミ^哪里。張一格說，研究過去的氣候可以提供一些這樣的視角，并有望幫助我們駕馭不確定的未來。

Because they trap tiny bubbles of air, ice cores are often used by climate scientists as a record of the historical CO2 levels in our planet's atmosphere. But these samples only go back hundreds of thousands of years and not millions.

由于冰芯能捕獲微小的氣泡，氣候科學(xué)家經(jīng)常用它來記錄地球大氣中二氧化碳的歷史含量。但這些樣本只能追溯到幾十萬年前，而不是幾百萬年前。

To dive deeper into Earth's history, Zhang and his colleagues turned to soil. As a natural part of the carbon cycle on Earth, soil creates carbonates when it is formed, and these tiny traces can be useful as indicators of past climates.

為了深入研究地球的歷史，張一格和他的同事們轉(zhuǎn)向了土壤。作為地球碳循環(huán)的自然組成部分，土壤在形成時會產(chǎn)生碳酸鹽，這些微小的痕跡可以作為過去氣候的指示。

Analysing carbonates in fossil soils from the Loess Plateau in China, the team was therefore able to reconstruct CO2 levels from millions of years ago.

通過分析中國黃土高原化石土壤中的碳酸鹽，該團隊得以重建數(shù)百萬年前的二氧化碳水平。

"The Loess Plateau is an incredible place to look at aeolian, or wind, accumulation of dust and soil," says Zhang.

張一格說:“黃土高原是一個不可思議的地方，可以看到風(fēng)、塵土和土壤的堆積。”

"The earliest identified dust on that plateau is from 22 million years ago. So, it has extremely long records."

“該高原上最早發(fā)現(xiàn)的塵埃來自2200萬年前。所以，它有非常長的記錄。”

While it's true that soil carbonates are only a proxy for ancient climates, the results from the Loess Plateau appear to match other estimates, which were made using ice cores and blue ice records instead.

雖然土壤碳酸鹽巖確實只是古代氣候的一個代表，但黃土高原的結(jié)果似乎與用冰芯和藍冰記錄得出的其他估計相符。

Zhang and his team, however, are still not content. They plan on refining their techniques for soil analysis to improve their estimates even more, potentially using the technique on soils as old as 23 million years.

然而，張一格和他的團隊仍然不滿意。他們計劃改進他們的土壤分析技術(shù)，以進一步提高他們的估計，有可能在2300萬年前的土壤上使用這項技術(shù)。

"Earth has a long history, and a lot of things from climate and life and environment have changed. ..

“地球有著悠久的歷史，從氣候、生命和環(huán)境等很多方面都發(fā)生了變化......，古氣候?qū)ξ覀兞私膺^去和預(yù)測未來很重要。”

The findings were published in Nature Communications.

研究結(jié)果發(fā)表在《自然通訊》雜志上。