又一种温室气体引起科学界注意，含量正快速升高
<p><span word="Carbon">Carbon</span> <span word="dioxide">dioxide</span> <span word="and">and</span> <span word="methane">methane</span> <span word="aren">aren</span>'<span word="t">t</span> <span word="the">the</span> <span word="only">only</span> <span word="greenhouse">greenhouse</span> <span word="gases">gases</span> <span word="the">the</span> <span word="world">world</span> <span word="needs">needs</span> <span word="to">to</span> <span word="worry">worry</span> <span word="about">about</span>. <span word="The">The</span> <span word="rapid">rapid</span> <span word="rise">rise</span> <span word="of">of</span> <span word="nitrous">nitrous</span> <span word="oxide">oxide</span> (<span word="N">N</span>2<span word="O">O</span>), <span word="colloquially">colloquially</span> <span word="known">known</span> <span word="as">as</span> '<span word="laughing">laughing</span> <span word="gas">gas</span>', <span word="is">is</span> <span word="no">no</span> <span word="joke">joke</span> <span word="either">either</span>.</p><p>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（<span word="N">N</span>2<span word="O">O</span>）含量飙升也是个很严重的问题。</p><p><span word="This">This</span> <span word="little">little</span>-<span word="known">known</span> <span word="greenhouse">greenhouse</span> <span word="gas">gas</span> <span word="may">may</span> <span word="not">not</span> <span word="be">be</span> <span word="as">as</span> <span word="prevalent">prevalent</span> <span word="nor">nor</span> <span word="as">as</span> <span word="long">long</span>-<span word="lasting">lasting</span> <span word="as">as</span> <span word="carbon">carbon</span> <span word="dioxide">dioxide</span>, <span word="but">but</span> <span word="it">it</span> <span word="is">is</span> <span word="hundreds">hundreds</span> <span word="of">of</span> <span word="times">times</span> <span word="more">more</span> <span word="potent">potent</span> <span word="and">and</span> <span word="can">can</span> <span word="stick">stick</span> <span word="around">around</span> <span word="in">in</span> <span word="the">the</span> <span word="atmosphere">atmosphere</span> <span word="for">for</span> <span word="more">more</span> <span word="than">than</span> <span word="a">a</span> <span word="century">century</span>.</p><p>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。</p><p><span word="Today">Today</span>, <span word="it">it</span>'<span word="s">s</span> <span word="released">released</span> <span word="mainly">mainly</span> <span word="through">through</span> <span word="human">human</span> <span word="agricultural">agricultural</span> <span word="practices">practices</span>, <span word="such">such</span> <span word="as">as</span> <span word="using">using</span> <span word="cheap">cheap</span> <span word="nitrogen">nitrogen</span> <span word="fertiliser">fertiliser</span>. <span word="And">And</span>, <span word="as">as</span> <span word="you">you</span>'<span word="ve">ve</span> <span word="no">no</span> <span word="doubt">doubt</span> <span word="guessed">guessed</span>, <span word="it">it</span>'<span word="s">s</span> <span word="also">also</span> <span word="a">a</span> <span word="main">main</span> <span word="contributor">contributor</span> <span word="to">to</span> <span word="ozone">ozone</span> <span word="depletion">depletion</span> <span word="and">and</span> <span word="global">global</span> <span word="warming">warming</span>.</p><p>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。</p><p><span word="To">To</span> <span word="make">make</span> <span word="matters">matters</span> <span word="worse">worse</span>, <span word="we">we</span>'<span word="ve">ve</span> <span word="seriously">seriously</span> <span word="underestimated">underestimated</span> <span word="its">its</span> <span word="use">use</span>. <span word="Since">Since</span> <span word="the">the</span> <span word="turn">turn</span> <span word="of">of</span> <span word="the">the</span> <span word="century">century</span>, <span word="new">new</span> <span word="measurements">measurements</span> <span word="reveal">reveal</span> <span word="atmospheric">atmospheric</span> <span word="N">N</span>2<span word="O">O</span> <span word="has">has</span> <span word="risen">risen</span> <span word="much">much</span> <span word="faster">faster</span> <span word="than">than</span> <span word="experts">experts</span> <span word="at">at</span> <span word="the">the</span> <span word="United">United</span> <span word="Nations">Nations</span> <span word="once">once</span> <span word="predicted">predicted</span>.</p><p>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。</p>
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