又一種溫室氣體引起科學界注意，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.
二氧化碳和甲烷並不是全世界唯一需要擔心的溫室氣體，俗稱“笑氣”的氧化亞氮（N2O）含量飆升也是個很嚴重的問題。
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.
這種鮮爲人知的溫室氣體可能不像二氧化碳那樣普遍那麼持久，但它的威力卻是二氧化碳的上百倍，可在大氣中逗留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.
現在這種氣體主要來源是人類的農業活動，比如使用廉價的氮肥。如你所料，它也是臭氧消耗和全球變暖的主要原因。
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.
更糟的是我們嚴重低估了它的作用。新的測量結果顯示，自本世紀初以來，大氣中氧化亞氮含量的上升速度比聯合國專家曾經預測的要快得多。
"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).
挪威大氣研究所的氣候科學家Rona Thompson說：“我們發現過去二十年內氧化亞氮排放量大大增加，2009年以後尤爲嚴重。”
"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."
“我們的判斷表明在過去十年間氧化亞氮排放速度比聯合國政府間氣候變化專門委員會利用排放因子法預計的快很多。”
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.
研究人員的計算並非基於通常從間接來源收集的人爲排放量，而是利用“自上而下”的方法，基於全球數十個大氣測量值進行計算。這些數據被用來預測1998 年至 2016年間陸地和海洋的氧化亞氮的動態變化。
