又一种温室气体引起科学界注意，含量正快速升高

Carbon dioxide and methane aren't the only greenhouse gases the world needs to worry about. The rapid rise of nitrous oxide (N2O), colloquially known as 'laughing gas', is no joke either.

二氧化碳和甲烷并不是全世界唯一需要担心的温室气体，俗称“笑气”的氧化亚氮（N2O）含量飙升也是个很严重的问题。

This little-known greenhouse gas may not be as prevalent nor as long-lasting as carbon dioxide, but it is hundreds of times more potent and can stick around in the atmosphere for more than a century.

这种鲜为人知的温室气体可能不像二氧化碳那样普遍那么持久，但它的威力却是二氧化碳的上百倍，可在大气中逗留100多年。

Today, it's released mainly through human agricultural practices, such as using cheap nitrogen fertiliser. And, as you've no doubt guessed, it's also a main contributor to ozone depletion and global warming.

现在这种气体主要来源是人类的农业活动，比如使用廉价的氮肥。如你所料，它也是臭氧消耗和全球变暖的主要原因。

To make matters worse, we've seriously underestimated its use. Since the turn of the century, new measurements reveal atmospheric N2O has risen much faster than experts at the United Nations once predicted.

更糟的是我们严重低估了它的作用。新的测量结果显示，自本世纪初以来，大气中氧化亚氮含量的上升速度比联合国专家曾经预测的要快得多。

"We see that the N2O emissions have increased considerably during the past two decades, but especially from 2009 onwards," says climate scientist Rona Thompson from the Norwegian Institute for Air Research (NILU).

挪威大气研究所的气候科学家Rona Thompson说：“我们发现过去二十年内氧化亚氮排放量大大增加，2009年以后尤为严重。”

"Our estimates show that the emission of N2O has increased faster over the last decade than estimated by the Intergovernmental Panel on Climate Change (IPCC) emission factor approach."

“我们的判断表明在过去十年间氧化亚氮排放速度比联合国政府间气候变化专门委员会利用排放因子法预计的快很多。”

Instead of basing their calculations on human emissions, which are usually gathered from indirect sources, the researchers used a 'top-down' approach, based on dozens of atmospheric measurements from around the world. These data were then used to predict N2O dynamics on land and in the ocean between 1998 and 2016.

研究人员的计算并非基于通常从间接来源收集的人为排放量，而是利用“自上而下”的方法，基于全球数十个大气测量值进行计算。这些数据被用来预测1998 年至 2016年间陆地和海洋的氧化亚氮的动态变化。