虽然大气层中的二氧化碳给地球起到保温作用，维系了生命，但浓度过高将导致温度升高，即全球气候变暖。科学家称，二氧化碳浓度升高最主要的原因是人类活动，其中以化石燃料燃烧为甚。

关键词：科普；二氧化碳浓度；大气层；译文

    There’s only one metric that really matters — and it’s telling us we’ve done less than zero to combat climate change

  只有一个指标是真正重要的 - 它告诉我们，我们在应对气候变化方面所做的努力远远不够

    The coal-fired Plant Scherer, one of the nation's top carbon dioxide emitters, in Juliette, Georgia.

  位于乔治亚州朱丽叶特的燃煤电厂舍尔是美国最大的二氧化碳排放者之一。

    AP/REX/Shutterstock

    Last week, an exquisitely sensitive instrument located in a metal shack on the top of Mauna Loa, a 13,679-foot-high volcano in Hawaii, recorded a terrifying human achievement: Thanks to our ever-increasing addiction to burning fossil fuels, the level of carbon dioxide in the Earth’s atmosphere has risen to 415 parts per million. This is the highest level it has been since human beings have lived on Earth. And it is further evidence (as if further evidence were needed) of just how hell-bent we are on cooking the planet we live on.

  上周，夏威夷海拔13,679英尺高的火山，莫纳罗亚山顶的一个传感器检测到了一个惊人的数据：由于我们对化石燃料需求的不断增加，地球大气层中二氧化碳的浓度已经超过了415 ppm。这是自人类在地球上生活以来的最高水平。这是进一步的证据(似乎还需要更进一步的证据)，证明我们是如何拼命地烹饪我们赖以生存的地球。

    For the planet itself, 415 ppm is no BFD. Over the past 4 billion years or so, it’s been much, much higher. But for us humans, 415 is a very dangerous number. The last time CO2 levels were at 415 ppm, during the Pliocene period about 3 million years ago, there was plenty of life on Earth, but the Earth itself was a radically different place. Beech trees grew near the South Pole. There was no Greenland ice sheet, and probably not a West Antarctic ice sheet, either. Sea levels were 50 or 60 feet (or more) higher.

  对于地球本身，415ppm并不是BFD。在过去40亿年左右的时间里，这个数字要高得多。但对我们人类来说，415是一个非常危险的数字。上一次二氧化碳浓度达到415ppm是在大约300万年前的上新世时期，当时地球上有很多生命，但地球本身是一个完全不同的地方。山毛榉树生长在南极附近。那里没有格陵兰冰盖，可能也没有南极西部的冰盖。海平面上升了50或60英尺(或更高)。

    That’s the world we’re creating for ourselves by pushing carbon dioxide levels to 415 ppm. Right now, a lot of atmospheric warming is being absorbed in the oceans. But those oceans are like a big flywheel, and the heat will be radiated out. That means, among other things, goodbye ice sheets, hello condo diving in Miami.

  这就是我们通过将二氧化碳浓度提高到415 ppm为自己创造的世界。现在，大量的大气变暖正被海洋吸收。这些海洋就像一个大飞轮，将热量散发出去。这意味着，除了别的以外，我们将再也见不到冰盖，可以在迈阿密的公寓中潜水。

    One way to think about carbon dioxide levels in the atmosphere is as a thermostat for the planet. As you’ll remember from third-grade science class, carbon dioxide is exhaled by animals, including humans, and inhaled by plants. It is also released when plants and animals decay, volcanoes erupt, and, most importantly, when we burn fossil fuels. Last year, we dumped about 37 billion tons of carbon dioxide into the atmosphere by burning fossil fuels. The more coal, oil and gas we burn, the faster that number rises. Before the Industrial Revolution, the level of carbon dioxide in the atmosphere was 280 ppm. Sixty years ago, it was 315 ppm. For the past few years, it has been rising by about 2 or 3 ppm a year 

  考虑大气中二氧化碳含量的一种方法是把它当作地球的恒温器。你会记得在三年级的科学课上，二氧化碳被动物包括人类呼出，被植物吸入。当动植物腐烂，火山爆发，最重要的是，当我们燃烧化石燃料时，它也会被释放出来。去年，我们通过燃烧化石燃料向大气排放了370亿吨二氧化碳。我们燃烧的煤、石油和天然气越多，这个数字增长得就越快。在工业革命之前，大气中的二氧化碳含量为280ppm。60年前，这个数字是315ppm。在过去的几年里，二氧化碳浓度每年上升2到3个ppm。

    That might not sound like much. However, carbon dioxide molecules happen to be very good at trapping heat in the atmosphere. Scientists have understood this very well since the 19th century. Carbon dioxide molecules are like the prison guards of the Earth’s atmosphere — they let sunlight in, but they don’t let heat out. Scientists argue about exactly how efficient carbon dioxide is at warming the Earth, but there is basic agreement that a doubling of carbon dioxide levels from 280 ppm will warm the Earth’s atmosphere by 2 to 3 degrees Celsius.

  这听起来可能不多。然而，二氧化碳分子恰好非常善于在大气中捕获热量。自19世纪以来，科学家们就非常了解这一点。二氧化碳分子就像地球大气层的狱警——它们让阳光进来，却不让热量出去。科学家们争论二氧化碳到底有多有效地使地球变暖，但基本的共识是，二氧化碳浓度从280ppm增加一倍，将使地球大气层升温2至3摄氏度。

    Right now, at 415 ppm, the climate has already warmed about one degree. And you don’t need to be a scientist to see the impacts: glaciers are melting, sea levels are rising, wildfires are growing more frequent, hurricanes and typhoons are growing more intense. The changes are so fast and so profound that, as a recent U.N. report suggested, more than a million species of animals and plants are at risk for extinction.

  现在，在415ppm的浓度下，气候已经变暖了一度。你不需要成为一名科学家就能看到这些影响：冰川正在融化，海平面正在上升，野火越来越频繁，飓风和台风越来越猛烈。变化如此之快、如此之深，正如联合国最近的一份报告所指出的那样，有100多万种动植物面临灭绝的危险。

    Measuring the level of carbon dioxide in the atmosphere is one of the great and underappreciated scientific accomplishments of our time. And most of the credit goes to Charles Keeling, a quiet geochemist from Scranton, Pennsylvania, who, in the 1950s, wondered if it would be useful to have a baseline measurement of the levels of carbon dioxide in the Earth’s atmosphere. In the 1950s, the heat-trapping properties of CO2 were well understood, but the link between burning fossil fuels and climate change was still tenuous. And actually measuring carbon dioxide levels in the atmosphere was more complex than it seemed, largely because carbon dioxide is a trace gas, measured in parts per million, and because the levels of carbon dioxide vary with local conditions, depending on plant life and the emissions of nearby power plants and other fossil fuel burning devices.

  测量大气中二氧化碳的含量是我们这个时代最伟大的科学成就之一，但却没有得到充分的重视。这主要归功于查尔斯·基林，一位来自宾夕法尼亚州斯克兰顿的地球化学家，在20世纪50年代，他想知道是否有必要对地球大气中的二氧化碳水平进行基线测量。在20世纪50年代，二氧化碳的吸热特性得到了很好的理解，但燃烧化石燃料与气候变化之间的联系仍然很薄弱。和实际测量大气中二氧化碳水平是比看起来复杂，主要是因为二氧化碳是一种微量气体，以ppm衡量，因为二氧化碳的浓度受当地条件影响，取决于植物和附近的电厂的排放以及其他化石燃料燃烧设备。

    In 1955, Keeling camped out at Big Sur State Park in California, collecting samples of air in flasks to measure their carbon dioxide content. Three years later, seeking even clearer air, he lugged his instruments up Mauna Loa in Hawaii and began taking measurements there.

  1955年，基林在加利福尼亚州的大苏尔州立公园露营，收集瓶子里的空气样本，以测量它们的二氧化碳含量。三年后，为了寻找更清洁的空气，他把仪器拖到夏威夷的莫纳罗亚山，开始在那里进行测量。

    Keeling quickly made two important discoveries. The first was that the Earth, in effect, breathes. As the seasons change, carbon dioxide levels in the atmosphere oscillate slightly. He immediately understood that this was the result of the seasonal growth of plants, especially trees. As trees sprouted leaves and grew over the spring and summer, carbon dioxide levels fell slightly. As the trees shed leaves in the fall and winter and the leaves began to decay, the carbon dioxide levels rose.

  基林很快有了两个重要的发现。首先，地球实际上是呼吸的。随着季节的变化，大气中的二氧化碳水平会轻微地波动。他立刻明白这是植物，尤其是树木，季节性生长的结果。随着树木在春季和夏季长出新叶，二氧化碳水平略有下降。随着树木在秋季和冬季落叶，树叶开始腐烂，二氧化碳水平上升。

    His second, and more ominous and consequential finding was that each year, the peak level of carbon dioxide in the atmosphere was a little higher than the year before. And that increase, it was clear, was due to the combustion of fossil fuels.

他的第二个、也是更不祥和更重要的发现是，大气中二氧化碳的峰值水平每年都略高于前一年。很明显，这种增长是由于化石燃料的燃烧。

 “It became clear very quickly that his measured CO2 increase was proportional to fossil fuel emissions and that humans were the source of the change,” James E. Hansen, director of NASA’s Goddard Institute for Space Studies, told the New York Times. “He altered our perspectives about the degree to which the Earth can absorb the human assault.”

  NASA戈达德太空研究所所长詹姆斯E.汉森对《纽约时报》表示:“很明显，他测量到的二氧化碳排放量与化石燃料排放成正比，而人类是这种变化的来源。”“他改变了我们对地球能够承受人类攻击的程度的看法。”

    Sixty-one years have now passed since Keeling took his first measurement on Mauna Loa (Keeling died in 2005; the work has now been taken over by his son, Ralph Keeling, a professor at Scripps Institution of Oceanography, which operates the Mauna Loa observatory), and the data over those years can be charted in what’s now known as the Keeling Curve, which measures the yearly growth of carbon dioxide levels in the atmosphere.

  自从基林在莫纳罗亚山进行第一次测量以来，已经过去了61年(基林于2005年去世;基林于2005年去世；工作现在已经被他的儿子，负责运营接管纳罗亚山天文台的斯克里普斯海洋研究所的教授拉尔夫·基林接管)，在过去的几年里，和数据可以绘制在现在称为林曲线，测量大气中二氧化碳含量的增长。

    When you look at this curve, two things are obvious. First, it is a smooth upward curve, with no breaks or dips or plateaus. Despite the decline in the cost of solar power, despite all the climate marches in the streets, despite the wildfires and melting glaciers and increasing summer heat, it is very obvious that, by the only metric that really matters, we have done less than zero to reduce the levels of carbon dioxide in the atmosphere.

  当你看这条曲线时，有两件事是显而易见的。首先，这是一条平稳向上的曲线，没有间断、下跌或平稳。尽管太阳能发电成本的下降，尽管气候在街上游行，尽管野火，融化的冰川和增加夏季炎热，很明显，通过真正重要的唯一指标，我们做不到零减少大气中二氧化碳的水平。

    The second thing you notice is that not only is the curve continuing to rise, but it is rising faster than ever before.

  你注意到的第二件事是，曲线不仅在继续上升，而且上升得比以往任何时候都快。

    Among other things, the Keeling curve is a perfect record of Homosapiens’ self-destructive impulse. We have known for precisely 61 years now that burning fossil fuels is warming the Earth’s atmosphere and putting the stability of our Goldilocks climate – the not-too-warm-not-too-cold world that has allowed humans to thrive over the last 10,000 years – at risk. And we have done nothing about it. In this sense, the Keeling Curve may turn out to be a kind a civilizational snuff film, a gruesome story, told in cool scientific fact, of our destruction of life as we know it on Earth.

  基林曲线是人类自我毁灭冲动的完美记录。61年前，我们就已经知道，燃烧化石燃料正在使地球的大气层变暖，的宜居气候 - 在过去的一万年里，这个不太温暖不太冷的世界使人类得以繁衍 - 的稳定性受到威胁。我们什么也没做。从这个意义上说，基林曲线可能是一部文明电影，一个可怕的故事，用冷静的科学事实讲述了我们对地球上生命的毁灭。

（责任编辑：李露）

（版权说明，转载自;科学猫科普）