这样的地球，我们从未生活过

在人类历史上，我们从未在这样的大气中生活过

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.

我们人类正式进入了未知领域。在人类在地球上行走的250万年里，我们从未经历过这样的大气层。

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.

对古代土壤的最新研究已经证实，过去60年的二氧化碳水平是人类历史上最高的。

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.

在整个更新世时期——25.8万年前开始——作者发现二氧化碳的浓度平均约为百万分之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，在过去60年左右的时间里，这种一致性似乎迅速瓦解。今天，研究结果表明，我们的星球在250万年来首次达到了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.

德州农工大学的地球科学家张一格解释说：“根据这项研究，从第一批直立人到1965年，我们生活在一个低二氧化碳的环境中——浓度低于百万分之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，目前的高二氧化碳环境不仅是对气候和环境的试验，也是对我们自己的考验。”

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.

要想知道我们要去哪里，首先需要知道我们去过哪里。张一格说，研究过去的气候可以提供一些这样的视角，并有望帮助我们驾驭不确定的未来。

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.

由于冰芯能捕获微小的气泡，气候科学家经常用它来记录地球大气中二氧化碳的历史含量。但这些样本只能追溯到几十万年前，而不是几百万年前。

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.

为了深入研究地球的历史，张一格和他的同事们转向了土壤。作为地球碳循环的自然组成部分，土壤在形成时会产生碳酸盐，这些微小的痕迹可以作为过去气候的指示。

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.

通过分析中国黄土高原化石土壤中的碳酸盐，该团队得以重建数百万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.

张一格说:“黄土高原是一个不可思议的地方，可以看到风、尘土和土壤的堆积。”

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

“该高原上最早发现的尘埃来自2200万年前。所以，它有非常长的记录。”

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.

虽然土壤碳酸盐岩确实只是古代气候的一个代表，但黄土高原的结果似乎与用冰芯和蓝冰记录得出的其他估计相符。

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，张一格和他的团队仍然不满意。他们计划改进他们的土壤分析技术，以进一步提高他们的估计，有可能在2300万年前的土壤上使用这项技术。

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

“地球有着悠久的历史，从气候、生命和环境等很多方面都发生了变化......，古气候对我们了解过去和预测未来很重要。”

The findings were published in Nature Communications.

研究结果发表在《自然通讯》杂志上。