碳排放是否会影响人类认知？

Lots of climate change literature points out that atmospheric carbon dioxide levels have never in the entire history of the human species been as high as they are today. Over the past 800,000 years, until the start of the Industrial Revolution, carbon dioxide in the atmosphere varied from about 200 to 300 parts per million (ppm). Since the early 1800s, the concentration has increased nearly 50%, from 280 ppm to 411 ppm in 2019.

许多气候变化的文献指出，在整个人类历史上，大气中的二氧化碳水平从来没有像今天这样高。在过去的80万年中，直到工业革命开始，大气中的二氧化碳含量在百万分之200到300之间变化。自19世纪初以来，该浓度已从280 ppm增加到2019年的411 ppm，增幅近50%。

This change, and even the whole idea of conditions unprecedented in our evolutionary history, often seems rather abstract. But carbon dioxide levels in the atmosphere could have direct effects on human physiology – perhaps eroding the keen intelligence and capacity for abstract thinking that we like to think of as a hallmark of our species, a new study suggests.

这种变化，甚至是我们进化史上史无前例的整个条件概念，往往显得相当抽象。但是，一项新的研究表明，大气中的二氧化碳水平可能会直接影响人类的生理机能——也许会侵蚀我们喜欢把抽象思维视为人类特征的敏锐智慧和能力。

There’s a fair bit of research on carbon dioxide and cognitive function in humans. This started out because scientists wanted to know about the effects on people in tight quarters like submarines and aircraft. More recently, they’ve looked at how carbon dioxide accumulates in densely populated, sometimes poorly ventilated indoor spaces such as schools and office buildings.

关于二氧化碳和人类认知功能的研究相当多。这是因为科学家们想知道像潜艇和飞机这样的狭小空间对人的影响。最近，他们研究了二氧化碳如何在人口稠密、有时通风不良的室内空间(如学校和办公楼)积聚。

Broadly speaking, such studies suggest that people’s cognitive functioning suffers when they are in a space with increased carbon dioxide in the air. Sometimes the relationship is linear (as in the case of overall decision-making ability) and sometimes there is a big drop off at higher concentrations (as with complex strategizing).

广义地说，这些研究表明，当人们身处空气中二氧化碳含量增加的空间时，他们的认知功能会受到影响。有时这种关系是线性的(如在整体决策能力的情况下)，有时在较高的集中度下会有很大的下降(如复杂的战略制定)。

But this research has received little attention from climate scientists until now, perhaps because climate scientists are mostly concerned with outdoor carbon dioxide levels and carbon dioxide-cognition research has focused on the indoor environment.

但这项研究迄今为止很少受到气候科学家的关注，也许是因为气候科学家主要关注室外的二氧化碳水平，而二氧化碳认知研究则侧重于室内环境。

A team of researchers from the University of Colorado and the University of Pennsylvania set out to bridge the gap. They started with scenarios developed by the Intergovernmental Panel on Climate Change, which predict atmospheric carbon dioxide concentrations at the end of the century ranging from 420 ppm if carbon emissions are drastically reduced to 930 ppm if emissions levels of recent years continue.

来自科罗拉多大学和宾夕法尼亚大学的一组研究人员着手缩小差距。他们从政府间气候变化专门委员会开发的情景开始，该情景预测到本世纪末大气中的二氧化碳浓度，如果碳排放量大幅减少，则为420 ppm，如果近年来的排放水平持续降低，则为930 ppm。

They accounted for higher carbon dioxide levels frequently seen in cities because of fossil fuel burning—a so-called “urban carbon dioxide dome” that amounts to about 66 ppm. Then they applied a set of equations based on known relationships between outdoor and indoor carbon dioxide levels. Indoor carbon dioxide concentrations are always higher than outdoor levels, to a degree depending on the building’s ventilation system, how many people are inside exhaling carbon dioxide with every breath, and how large the space is.

它们造成了由于化石燃料燃烧而在城市中经常出现的较高的二氧化碳含量，所谓的“城市二氧化碳圆顶”约为66 ppm。然后，他们根据室外和室内二氧化碳水平之间的已知关系应用了一组方程式。室内二氧化碳的浓度总是高于室外，在一定程度上取决于建筑物的通风系统，每口呼气中有多少人呼出二氧化碳以及空间有多大。

Finally, they cross-referenced the resulting indoor carbon dioxide concentrations with the results of studies on carbon dioxide and cognition. “The model predictions are quite arresting,” the researchers write in the journal GeoHealth. If today’s high carbon emissions were to continue, “we may be in for a ~25% reduction in our indoor basic decision-making ability, and a ~50% reduction in more complex strategic thinking, by the year 2100 relative to today.”

最后，他们将得出的室内二氧化碳浓度与二氧化碳和认知研究的结果交叉引用。研究人员在《地球健康》(GeoHealth)杂志上写道：“模型预测相当令人信服。”。如果今天的高碳排放继续下去，“到2100年相对今天，我们的室内基本决策能力可能会下降约25%，更复杂的战略思维可能会下降约50%。”

“These results are almost entirely avoidable” if emissions are reduced to levels consistent with the Paris Agreement, they add.

他们补充说，如果排放量减少到与《巴黎协定》一致的水平，“这些结果几乎完全可以避免。”。

The results are a first pass at the problem—the researchers’ model is relatively simple—but they show that more attention to these questions is needed.

研究结果是解决这个问题的第一步。研究者的模型相对简单，但他们表明需要更多的关注这些问题。