How Much CO2 Will We Have in the Air This Year?

ABSTRACT 摘要

“二氧化碳（CO2）是导致全球变暖的气体。当我们燃烧燃料时（如开车或发电），我们向空气中排放出更多的CO2，这就导致了气候变化。大自然十分善于除去空气中的 CO2。树木需要依靠它生长，海洋可以将它溶解。但并不是所有的CO2都能得以清除，因此，每年大气中CO2的含量都会增加。每年，我们都会试图预测CO2会增加多少。为了准确预测CO2，我们必须了解人类活动和自然生态系统是如何相互影响的。在这篇文章里，我们将解释如何进行这种预测。对于2020年，我们预测CO2的含量会比平均含量增长更快。

Carbon dioxide (CO2) is a gas that contributes to global warming. When we burn fuel (for example to drive cars or to generate power) we put more CO2 into the air, which contributes to climate change. Nature is very good at removing CO2 from the air. Trees need it to grow and the oceans can dissolve it. But not all the new CO2 is removed, so the amount in the air increases each year. Every year, we try to predict how much more CO2 we will have. For an accurate CO2 forecast, we must understand how human activity and natural ecosystems affect each other. In this article, we explain how we can make this forecast. For 2020, we predict that CO2 levels will increase faster than average.”

什么是碳循环？

WHAT IS THE CARBON CYCLE?

二氧化碳（CO2）在大气中天然存在。它是一种温室气体---你可能想从Jonny Williams的文章里读到更多关于它是如何导致气候变化的信息。CO2对植物的生长是不可或缺的。当植物生长时，它们从空气中吸收CO2。当植物凋零时，CO2会重新释放回大气中。这就所谓的碳循环。这有点像你可能已经知晓的水循环：当雨水落到陆地上时，水通过河流流向大海，然后水可以再次蒸发，再次以雨水的形式落下。水就是在一个大循环中转来转去。

Carbon dioxide(CO2) exists naturally in the earth’s atmosphere. It is agreenhouse gas—you might want to read more about this in Jonny Williams’s article [1] which explains more about how this causes climate change. It is also essential for plants to grow. When plants grow, they absorb CO2from the air. When they die, theCO2goes back to the atmosphere. This is known as thecarbon cycle. It is a bit like the water cycle, which you probably know about: when it rains on land, the water flows through rivers into the sea. Then it can evaporate again before falling once more as rain. The water just goes round and round in a big cycle.

类似的情况也发生在CO2上（图1）。它可以被陆地和海洋上的植物吸收（我们把生活在海洋里的那种微小植物称为浮游植物）。通过光合作用，植物将CO2转化成它们的树干、叶子或躯干生长时所需的碳元素。当植物凋零时，这些碳元素会回归土壤，在土壤里，细菌和许多微生物群会吃这些碳元素，并将其转化为CO2。大约200年前，在人类开始燃烧许多矿石燃料之前，碳在循环中的总量一直相等。但如今，人类大面积砍伐森林、燃烧煤和石油，增加了碳循环里的碳元素。

Something similar happens for CO2(Figure 1). It can be absorbed by both plants on land and in the ocean (tiny plants called phytoplankton). Via photosynthesis, plants turn the CO2 into the carbon needed to grow their trunks, leaves, or bodies. When the plants die, the carbon goes into the soil where bacteria and microbes eat it and turn it back into CO2. Before humans began to burn lots offossil fuels about 200 years ago, the total amount of carbon in the cycle remained the same. But now, humans have added more carbon to the carbon cycle by cutting down trees, called deforestation, and burning coal and oil.

图1-全球碳循环

树木和植物通过光合作用吸收二氧化碳并将其转化为生长所需的碳。当凋亡的植物和叶子腐烂时，碳以二氧化碳的形式回到大气中。海洋吸收碳并将其释放回大气中。人类活动，如燃烧矿石燃料和砍伐树木，会使更多的二氧化碳进入大气层。

Figure 1 - The global carbon cycle.

Trees and plants absorb CO2 and turn it into the carbon they need to grow, through photosynthesis. The carbon returns to the atmosphere as CO2 when dead plants and leaves decay. Oceans absorb carbon and release it back to the atmosphere. Human activities, like burning fossil fuels and cutting down trees, put more CO2 into the atmosphere.

空气中的CO2是如何随历史的变迁而变化的？

HOW HAS CO2 IN THE AIR CHANGED OVER HISTORY?

在1958年，科学家开始直接测量空气中的CO2。在成千上万年里，它一直保持不变。如果你检测一百万个空气分子，这些空气分子中有208个CO2分子---我们把这称为ppm（ 百万分之一），因此，我们会说在许多年来CO2的浓度一直聚集在280ppm。大约200年前，由于工业化的发展，人类开始砍伐越来越多的森林以及燃烧像煤和天然气的矿石燃料。这些行为使得更多的CO2排放到大气中。自大约1850年以来，CO2在空气中的浓度一直在增加。科学家们第一次测量空气中的CO2是在夏威夷岛的莫纳罗亚（Mauna Loa），那里有一座大火山，火山顶上有一个观测站。因为这里远离污染较严重的大面积陆地，所以这里是测量CO2的好地方。一个叫Charles Keeling的著名科学家一直在进行这些测量，如今我们可以观察到，从2016年开始，大气中CO2的浓度已经高于440ppm（图2）。这也是自工业革命以来，我们的气候变暖了1 °C左右的主要原因。

In 1958, scientists started to measure the CO2in the air directly. For thousands of years, it was constant. If you examined one million molecules of air, 280 of these would be CO2. We call this parts per million (ppm). So, we would say that the CO2concentration for many years was 280 ppm. About 200 years ago as industrialization began, humans started to cut down more and more forests and to burn fossil fuels, like coal and gas. These activities put more CO2into the air. Since about 1850, the concentration of CO2in the air has increased. Scientists first measured CO2in the air in Mauna Loa, Hawaii, where there is an observatory on top of a large volcano. This is a good place to measure CO2because it is away from large land areas where there is more pollution. A famous scientist called Charles Keeling kept these measurements going [2] and now we can see that, since 2016, CO2has reached more than 410 ppm (Figure 2). This is the main reason our climate has warmed by about 1°C since the industrial revolution.

图2 - 来自斯克里普斯海洋学研究所的科学家在夏威夷莫纳罗亚的一个观测站测量空气中的二氧化碳（照片）1。

图中显示，在人类活动开始向空气中释放更多二氧化碳之前，二氧化碳已经从大约280ppm增加到2020年的410ppm以上。

Figure 2 - CO2 is measured in the air at an observatory in Mauna Loa, Hawaii (photograph), by scientists from the Scripps Institute of Oceanography.1

The graph shows that CO2 has increased from about 280 ppm before human activity started to put lots more CO2 into the air, to more than 410 ppm in 2020.

是什么让大气中的二氧化碳含量发生变化？

WHAT MAKES THE AMOUNT OF CO2 IN THE ATMOSPHERE CHANGE?

我们知道人类活动向大气中排放了更多的CO2，但我们也知道碳循环会除去一部分CO2。这就使得了解有多少CO2会释放到大气中变得十分复杂。科学家们一直在努力测量CO2的变化，现在我们知道大约有一半的CO2排放会被截留在空气中。植物和海洋吸收了其余的部分。换言之，如果我们燃烧矿石燃料，制造了4吨的CO2，那么大约2吨的CO2会被截留在大气中，1吨被植物吸收，1吨被海洋吸收。

We know that human activity puts more CO2 in the atmosphere, but we also know that the carbon cycle removes some of it. This makes it quite complicated to understand how much more CO2 will continue to be added to the air. Scientists have worked very hard to measure what is happening with CO2, and now we know that about half of the CO2 emissions stay in the air. Plants and oceans absorb the rest. In other words, if we burn fossil fuels and create 4 tons of CO2, then about 2 tons will stay in the air, 1 ton will be absorbed by plants, and 1 ton by the oceans.

我们知道空气中CO2的含量每年都会增加。这个趋势是由于人类燃烧矿石燃料和砍伐森林造成的。我们也可看到，在某些年份CO2比其他年份增加得更快。哪怕我们燃烧燃料的量大致相同，但不同类型的天气一样会造成不同的结果。在某些年份天气偏炎热，而某些年份天气偏寒冷，这些天气的差异可以改变CO2被重吸收的量。一种被称为厄尔尼诺的天气现象大约每4年出现一次，它会使得某些地方比平常更炎热，更干燥。天气变炎热会减缓植物的生长以及引起更多的火灾，这就意味着空气中CO2的含量比平常多。图3显示出 CO2每年的变化---我们把这称为增长率。在炎热的年份，CO2的增长率会比寒冷的年份高。

We know that the amount of CO2 in the air increases every year. This trend is caused by people burning fuels and cutting down trees. We can also see that, in some years, CO2 increases more quickly than in others. This is true even if the amount of fuel we burn is about the same, and results from different types of weather. Some years are hot and some are cold. Weather differences can change the amount of CO2 that is absorbed. A weather pattern called El Niño happens approximately every 4 years, making some places hotter and drier than normal. The warmer weather can slow down plant growth and cause more fires, which means more CO2 in the air than normal. Figure 3 shows the changes in CO2 each year—we call this the growth rate. In hot years, the growth rate is greater than in cold years.

图3 - CO2增长率，即空气中二氧化碳每年增加的量，用黑线表示

蓝线表示太平洋热带地区温度高于或低于正常水平的程度。你可以看到，二氧化碳每年增加约2ppm，整个期间平均每年增长1.6ppm。从2000年开始，平均每年的增长速度是2.2ppm。如红色箭头所示，厄尔尼诺造成的炎热年份会导致二氧化碳增加。

Figure 3 - The CO2 growth rate, which is the amount that CO2 in the air increases every year, is shown with a black line.

The blue line shows how much the tropical Pacific Ocean temperature is above or below normal. You can see that CO2 increases by about 2 ppm each year, with an average growth of 1.6 ppm per year over this whole period. Since 2000, the average growth rate was 2.2 ppm per year. Hot years caused by El Niño lead to greater CO2 growth, as you can see by the red arrows.

CO2预测

CO2 FORECASTING

预测最终会有多少CO2排放到空气中的过程叫CO2预测。为了精确预测CO2的含量，我们必须明白三个问题：全世界使用了多少燃料，砍伐了多少树木，以及天气将如何改变自然过程。

The process of predicting how much CO2 will end up in the air each year is called CO2 forecasting. For accurate CO2 forecasting, we must understand three processes: how much fuel the world is using, how much forest is being cut down, and how the weather will change natural processes.

在2015年年末，我们从季节性天气预报中得知一个庞大的厄尔尼诺即将到来。所以，我们预计空气中CO2的增长速度会比先前快。我们做了一个预测，并写了一篇论文。在2016年年末，我们在莫纳罗亚对CO2进行了测量，以查核我们的预测是否准确。事实证明，我们的预测是正确的。那是有史以来CO2增幅最大的一次，CO2目前的浓度超过了400ppm。如今，我们每年都会再次对下一年CO2浓度进行预测。 

At the end of 2015, we knew from seasonal weather forecasts that a big El Niño was going to happen. So, we expected that CO2 in the air would grow more quickly than ever before. We made a forecast and wrote a paper about this [3]. At the end of 2016, we measured the CO2 at Mauna Loa to check whether our forecast was right. It turned out we had correctly predicted the biggest CO2 increase ever seen, and that CO2 was now more than 400 ppm. Now, every year, we repeat our CO2 forecast for the next year.2

在2020年，我们的季节性天气预报预测将会有一个小型的厄尔尼诺，这意味着CO2将比往常增长得更快，但这并不会成为一个记录。如果我们的预测是正确的，那这将是CO2的第四次大增长。同时我们也预计世界将燃烧与去年差不多的燃料量，释放出大约420吨的CO2（这相当于全球每人5吨多的二氧化碳）!当我们综合这些事实，我们便可预算到CO2浓度会增加2.74ppm，以及在2020年将达到414.2ppm。这是一百多万年以来CO2达到的最高水平。

For 2020, our seasonal forecast predicts that there will be a small El Niño. This means CO2 will grow faster than usual, but it will not be a record. If our forecast is correct, it will be the fourth biggest increase seen in CO2. We also expect that the world will burn about the same amount of fuel as last year [4], releasing about 42 billion tons of CO2, which is more than 5 tons of CO2 for every person in the world! When we combine these facts, we can predict that CO2 will increase by 2.74 ppm and the average for 2020 will be 414.2 ppm. This is the highest CO2 level for over a million years. 

你可能已经看到澳大利亚在2019年年末至2020年年初天气炎热，造成大型山火的新闻。山火使很多人、家以及动物受到影响，也烧毁了许多树木，向大气中排放出更多的CO2。从我们的分析来看，我们认为这些山火将CO2的增长速度比往年增加了2%。我们也知道，由于新冠肺炎的大流行，人们减少了燃料的使用，尤其是在交通上。这意味着2020年CO2的排放量会低一些，所以我们预计CO2浓度的增幅会减少0.03ppm。

You may have seen the news that Australia had some very hot weather at the end of 2019 and early 2020, which led to some huge fires. The fires affected lots of people, homes, and animals, but they also burnt down many trees, which put more CO2 in the atmosphere. We can use satellites to measure how many fires there were and to estimate how much CO2 this caused. From our analyses, we think that these fires made the CO2 increase about 2% faster than previous years. We also know that people have used less fuel, especially for transport, because of the Covid-19 pandemic. This means CO2 emissions might be a bit smaller in 2020 [5], so we expect about 0.3 ppm smaller growth3 of CO2.

为什么CO2如此重要？

WHY IS CO2 FORECASTING IMPORTANT?

我们知道，我们的气候正在发生变化，这些变化正对世界各地的人们带来一些毁灭性的影响。我们看到越来越多的风暴、旱灾以及越来越多像澳大利那样的山火。其中一些现象可能无论如何都会发生，但随着气候变化，它们会发生得越来越频繁。我们明白，竭尽全力阻止气候变化恶化尤为重要。为了阻止其恶化，我们应该减少新生CO2排放到空气中的含量。如果我们能理解自然过程是如何从大气中吸收CO2的，那么便可以计算出我们必须减少多少燃料的使用。我们把这称为碳预算。你在花钱时可能会有一个预算，这预算会告诉你在食物、衣服等等上要花多少钱。科学家可以通过计算得出一个碳预算，它可以衡量在气候变化变得过于危险前我们可以使用多少燃料。

We know that our climate is changing and that these changes are having some devastating effects on people around the world. We have seen more storms, more droughts, and more fires like those in Australia. Some of these might happen anyway, but with climate change we know they will happen more often. We know it is extremely important to try to stop climate change from getting even worse. To stop it from getting too bad, we should all try to reduce the amount of new CO2 we put in the air. If we can understand how natural processes take CO2 out of the atmosphere, then we can calculate how much we must reduce our use of fuel. We call this a carbon budget. You might have a budget for spending your money, which tells you how much to spend on food, clothes, and so on. Scientists can work out a carbon budget, which measures how much fuel we can use before climate change becomes too dangerous.

CO2的预测是帮助我们了解碳循环研究的一部分。如今我们知道，我们可以非常精确地预测世界碳循环1年的情况。这将帮助我们改善未来多年预测CO2增长的方式，这样可以帮助世界谋划避免气候变化带来危险的方法。

Our CO2 forecast is part of the research that we need to help understand the global carbon cycle. We now know that we can predict the world’s carbon cycle very accurately for 1 year. This will help us improve how we predict CO2 growth for many years in the future, which can help the world plan ways to avoid the dangers of climate change.

STRETCH AND CHALLENGE!

放轻松，尝试挑战一下吧！

如果你喜欢数学，以下是我们用来做预测的方程式。

我们把燃烧化石燃料和砍伐森林所产生的CO2加在一起。我们把这称为排放量，并使用符号“E”表示。在2018年，369亿吨CO2来自化石燃料，55亿吨CO2来自森林砍伐。所以，CO2排放量为E=369+55=424亿吨。

我们还需要一个海洋温度的预测。我们把这称为 "N"，代表厄尔尼诺现象。根据气象局的预测，2020年的N=0.59℃。

现在，我们可以运用一个方程式来计算2020 CO2的增长速率，将E与N乘以一些被称为系数的数字，系数是通过观察过去的数据并使用数学回归技术来确定的。

CO2增长率 = 0.07 + (0.43 × N) + (0.057 × E)

= 0.07 + 0.25 + 2.42

= 2.74 ppm

现在请畅想一下，在2021年，排放量可能会增加到430亿吨，但我们可能会有一个使天气变寒冷的拉尼娜现象，以及N = -1℃。你能算出二氧化碳的增长率是多少吗？

If you like maths, here is the equation we use to make our forecast.

We add together the CO2 made by burning fossil fuels and deforestation. We call this the emissions, and use the symbol “E”. For 2018, 36.9 billion tons of CO2 came from fossil fuels and 5.5 billion tons from deforestation [4]. So, E = 36.9 + 5.5 = 42.4 billion tons of CO2.

We also need a forecast of the ocean temperatures. We call this “N” to stand for El Niño. The Met Office forecast predicts N = 0.59°C for 2020.

Now we can calculate the CO2 growth rate for 2020 using an equation, multiplying E and N by some numbers called coefficients. The coefficients were determined by looking at the data for the past and using a mathematical technique called regression.

CO2 growth rate = 0.07 + (0.43 × N) + (0.057 × E)

= 0.07 + 0.25 + 2.42

= 2.74 ppm

Now imagine that, in 2021, emissions might increase to 43 billion tons, but maybe we might have a cold La Niña and N = −1°C. Can you work out what the CO2 growth rate would be?

Glossary 术语表

Carbon Dioxide (CO2):↑A gas in the atmosphere that is created when we burn fossil fuels. CO2is a greenhouse gas and can stay in the air for many years. It is the main cause of climate change.

二氧化碳（CO2）：大气中的一种气体，是我们燃烧矿石燃料时产生的。二氧化碳是一种温室气体，可以在空气中停留多年。它是导致气候变化的主要原因。

Greenhouse Gas:↑A gas in the atmosphere which can absorb heat and cause the planet to warm up. These occur naturally, such as carbon dioxide and water vapor, but human activity is putting more greenhouse gases into the air leading to the planet getting warmer.

温室气体：大气中的一种气体，它可以吸收热量，使地球变暖。这些气体是自然产生的，如二氧化碳和水蒸气，但人类活动正将更多的温室气体投入空气，导致地球变暖。

Carbon Cycle:↑The movement of carbon through nature—plants absorb CO2from the air as the grow, and release it again when they die. The water in the oceans dissolves CO2. This cycle is called the carbon cycle.

碳循环：碳在自然界的流动--植物在生长过程中吸收空气中的二氧化碳，并在死亡时将其再次释放。海洋中的水会溶解大气中的二氧化碳。这个循环被称为碳循环。

Fossil Fuel:↑Fuels, such as coal, oil, and natural gas that were formed millions of years ago when plants and animals died and became buried. Burning fossil fuels creates CO2, which goes into the atmosphere.

矿石燃料：煤、石油、天然气等燃料是几百万年前动植物死亡后被掩埋后形成的。燃烧化石燃料会产生二氧化碳，进入大气层。

El Niño:↑A weather pattern that happens approximately every 4 years. The temperature of the Pacific Ocean gets warmer and this leads to hotter and drier weather in many regions. The opposite pattern is called La Niña, which leads to cooler temperature around the world.

厄尔尼诺：一种大约每4年发生一次的天气现象。太平洋的温度升高，导致许多地区的天气变得更热、更干燥。与此相反的模式被称为拉尼娜，它会导致世界各地的气温降低。

Growth Rate (of CO2):↑We know that there is more CO2in the air every year, because we can measure it. But some years it increases faster than others. The amount that it changes is called the “growth rate”.

（二氧化碳的）增长率：↑ 我们知道空气中的二氧化碳每年都在增加，这是因为我们对它进行测量。但有些年份它的增长速度比其他年份快。这种变化量被称为 "增长率"。

CO2Forecasting: ↑ We know that the amount of CO2 in the air will increase every year, but we do not know exactly how much. We use our knowledge of the carbon cycle to predict how much more CO2 we will get. This is our CO2 forecast.

CO2预测：我们知道空气中的二氧化碳量每年都会增加，但我们不知道具体增加多少。我们用碳循环的有关知识来预测我们将增加多少二氧化碳。这就是我们的二氧化碳预测。

Carbon Budget: ↑ We know that putting more CO2 into the air causes climate change. By understanding how the carbon cycle works we can work out how much CO2  will cause a dangerous level of climate change. We need to make sure that we burn less fossil fuel than this amount of carbon—which we call the carbon budget.

碳预算：我们知道向空气中排放更多的CO2会造成气候变化。通过了解碳循环是如何运作的，我们便可计算出多少二氧化碳会达到气候变化的危险程度。我们需要确保我们燃烧的化石燃料少于这个碳量，我们称之为碳预算。

附上作者信息：

小婧唠叨：

作者信息没时间翻译啦，有时间再补过来哈，望各位见谅。

文章谈到厄尔尼诺和拉尼娜的天气现象，是我们高中海洋地理要学的知识，不过个人觉得文章解释的不够详细，具体的各位感兴趣可以去网上搜索相关资料深入了解。

这篇文章翻译只花了一个星期翻译，所以很匆忙。如有不足瑕疵之处，还请海涵！