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近期發表在《環境科學與技術》上的一項研究論文指出，在行程距離相同的情況下，駕車出行對全球升溫帶來的長期影響要超過乘飛機出行。不過，從短期來看，飛機對氣候的不利影響要更大一些，因為飛機在高空中飛行時對云層和臭氧層造成破壞從而導致短時的升溫效應。這項研究是由奧地利和挪威的一組科學家進行的，他們在研究中對比了各種交通工具排放的氣體對全球變暖產生的短期和長期影響。
研究發現，按單個乘客每公里排放的二氧化碳量來比較，駕車出行比乘機的排放量要高；而且，由于二氧化碳在空氣中滯留的時間較長，由此對氣候變化產生的長期影響也就更大一些。 在貨物運輸方面，等距離運送等量貨物時，飛機對氣溫升高產生的影響是普通卡車的7到35倍，而船運產生的長期影響卻是卡車25分之一。
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Driving alone in a car increases global temperatures in the long run more than making the same long-distance journey by air according to a new study. |
Driving alone in a car increases global temperatures in the long run more than making the same long-distance journey by air according to a new study. However, in the short run traveling by air has a larger adverse climate impact because airplanes strongly affect short-lived warming processes at high altitudes.
The study, published in the journal Environmental Science & Technology by a team of researchers from Austria and Norway, compares the impacts on global warming of different means of transport. The researchers use, for the first time, a suite of climate chemistry models to consider the climate effects of all long- and short-lived gases, aerosols and cloud effects, not just carbon dioxide, resulting from transport worldwide.
In the long run the global temperature increase from a car trip will on average be higher than from a plane journey of the same distance. However, in the first years after the journey, air travel increases global temperatures four times more than car travel. Passenger trains and buses cause four to five times less impact than automobile travel for every kilometer a passenger travels. The findings prove robust despite the scientific uncertainties in understanding the earth's climate system.
"As planes fly at high altitudes, their impact on ozone and clouds is disproportionately high, though short lived. Although the exact magnitude is uncertain, the net effect is a strong, short-term, temperature increase," explains IIASA's Dr Jens Borken-Kleefeld, lead author of the study. "Car travel emits more carbon dioxide than air travel per passenger kilometer. As carbon dioxide remains in the atmosphere longer than the other gases, cars have a more harmful impact on climate change in the long term."
The research also showed that when it comes to freight transport, moving goods by planes will increase global temperatures between 7 to 35 times more than moving the same goods the same distance in an average truck. Shipping on the contrary exerts 25 times less warming in the long run, and even cools on shorter time scales.
"Ships contribute to global warming through carbon dioxide, ozone and soot. Currently they also emit relatively large amounts of sulfur dioxide which forms sulfate particles in the atmosphere. Those particles cool the planet by reflecting solar radiation back into space," says co-author Dr Jan Fuglestvedt from CICERO. "In the first decades after a shipment, the cooling effect more than offsets the warming. And because of the large volumes of goods traded by ship, global trade actually counteracts some of the temperature increases caused by global passenger travel. However, in the long term all means of motorized transport add to global warming."
The study concluded that as climate change acts at various time scales, it is important to have policies to reduce both the air pollutants that have strong, short-term impacts and the long-lived gases that lead to long-term warming. In addition, Dr Borken-Kleefeld argues: "A comprehensive strategy to tackle climate change caused by the transport sector is actually to minimize the demand for transport."
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(Agencies)
（中國日報網英語點津 Helen 編輯）
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