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科学美国人60秒:飞机高度的变化减少了气候变化的轨迹

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Jet Altitude Changes Cut Climate Changing Contrails
 飞机高度的变化减少了气候变化的轨迹

 
Airplanes account for about three percent of the climate-altering carbon dioxide emissions we add to the atmosphere. But planes are warming the planet in another way. “So if you look up in the sky, you probably see at some point an aircraft, and behind that aircraft are white fluffy streaks. And that's what we call a contrail.”
 
我们向大气中排放的改变气候的二氧化碳中,飞机约占3%。但是飞机正以另一种方式使地球变暖。“所以如果你抬头看天空,你可能在某个地方看到一架飞机,飞机后面是白色的绒毛条纹。这就是我们所说的轨迹。”
 
Imperial College London engineer Marc Stettler.Contrails are made up of ice crystals that form when aircraft engines emit exhaust that hits the cold air. The ice crystals reflect incoming light from the sun back into space, which has a cooling effect on the atmosphere. But the contrails also stop heat coming up from the ground from escaping into space.
 
帝国理工学院工程师马克·斯特勒。飞机尾迹是由冰晶构成的,当飞机引擎排放的废气撞击冷空气时,冰晶就会形成。冰晶将来自太阳的光线反射回太空,对大气产生冷却作用。但是这些尾迹也阻止了来自地面的热量进入太空。
 
“It's reflected back down towards the ground. And so that's a warming effect.”Stettler says on balance, contrails warm the atmosphere more than they cool it.  “And that's primarily because the cooling effect due to reflecting of sunlight can only happen during the day when the sun’s shining, whereas the warming effect due to trapping of outgoing heat happens all of the time.”
 
“它被反射回地面。这就是变暖效应。斯泰特勒说,总的来说,飞机尾迹对大气的加热作用大于冷却作用。“这主要是因为阳光反射产生的冷却效应只在白天阳光灿烂的时候才会发生,而吸收热量产生的变暖效应则一直都在发生。”
 
Some contrails can form clouds that last for up to 18 hours. During that time they spread out, trapping even more heat. This process allows contrails to warm the planet about as much as the carbon dioxide emissions from aircraft.
 
一些尾迹可以形成持续18个小时的云。在此期间,它们分散开来,吸收了更多的热量。这一过程使飞机尾迹使地球变暖的程度相当于飞机排放的二氧化碳。
 
But when Stettler and his team analyzed flight data they obtained of Japan airspace, they found that most contrail warming was caused by just two percent of flights. And most of those flights originated in the late afternoon—because as the sun goes down, cooling can no longer offset the warming.
 
但是当Stettler和他的团队分析他们获得的日本领空的飞行数据时,他们发现大部分的尾迹变暖是由2%的飞行引起的。这些航班大多是在傍晚起飞的,因为随着太阳落山,降温已无法抵消变暖的影响。
 
“And the warming effect persists throughout the evening into the night.”But what if the contrails that contribute the most to warming could be eliminated? Such a change could be achieved if aircraft avoided flying in the thin layers of humidity where contrails form.
 
“这种变暖效应会持续整个晚上直到晚上。“但是,如果造成全球变暖最严重的飞机尾迹能够被消除呢?”如果飞机避免在形成尾迹的薄层潮湿环境中飞行,这样的改变是可以实现的。
 
“By changing the altitude only by a couple of thousand feet, either up or down, it would no longer form a contrail. And so what we found in this study was that by changing the altitude of less than two percent of flights, we could actually get rid of just under 60 percent of the warming effect due to contrails.”The study is in the journal Environmental Science & Technology.
 
“只要把高度向上或向下改变几千英尺,飞机就不会再形成一条轨迹。因此,我们在这项研究中发现,通过改变飞行高度不到2%的飞机,我们实际上可以消除近60%的由飞机尾迹造成的变暖效应。这项研究发表在《环境科学与技术》杂志上。
 
This improved understanding of how to manage contrails presents an opportunity for the aviation industry to reduce its global environmental impact. Think of it as a silver lining in those contrail clouds.
 
这种对如何管理飞机尾迹的改进,为航空业提供了一个减少其全球环境影响的机会。把它想成是那些尾云中的一线曙光。
 

 
Jet Altitude Changes Cut Climate Changing Contrails
 
Airplanes account for about three percent of the climate-altering carbon dioxide emissions we add to the atmosphere. But planes are warming the planet in another way. “So if you look up in the sky, you probably see at some point an aircraft, and behind that aircraft are white fluffy streaks. And that's what we call a contrail.”
 
Imperial College London engineer Marc Stettler.Contrails are made up of ice crystals that form when aircraft engines emit exhaust that hits the cold air. The ice crystals reflect incoming light from the sun back into space, which has a cooling effect on the atmosphere. But the contrails also stop heat coming up from the ground from escaping into space.
 
“It's reflected back down towards the ground. And so that's a warming effect.”Stettler says on balance, contrails warm the atmosphere more than they cool it.  “And that's primarily because the cooling effect due to reflecting of sunlight can only happen during the day when the sun’s shining, whereas the warming effect due to trapping of outgoing heat happens all of the time.”
 
Some contrails can form clouds that last for up to 18 hours. During that time they spread out, trapping even more heat. This process allows contrails to warm the planet about as much as the carbon dioxide emissions from aircraft.
 
But when Stettler and his team analyzed flight data they obtained of Japan airspace, they found that most contrail warming was caused by just two percent of flights. And most of those flights originated in the late afternoon—because as the sun goes down, cooling can no longer offset the warming.
 
“And the warming effect persists throughout the evening into the night.”But what if the contrails that contribute the most to warming could be eliminated? Such a change could be achieved if aircraft avoided flying in the thin layers of humidity where contrails form.
 
“By changing the altitude only by a couple of thousand feet, either up or down, it would no longer form a contrail. And so what we found in this study was that by changing the altitude of less than two percent of flights, we could actually get rid of just under 60 percent of the warming effect due to contrails.”The study is in the journal Environmental Science & Technology.
 
This improved understanding of how to manage contrails presents an opportunity for the aviation industry to reduce its global environmental impact. Think of it as a silver lining in those contrail clouds.
 
 


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