People who own all-electric cars where coal generates the power may think they are helping the environment, but a new study finds their vehicles actually make the air dirtier, worsening global warming.

The controversial study raises major questions over the future of “green” cars.

“Unfortunately, when a wire is connected to an electric vehicle at one end and a coal-fired power plant at the other end, the environmental consequences are worse than driving a normal gasoline-powered car,” said Ken Caldeira of the Carnegie Institution for Science, who wasn’t part of the study but praised it.

Driving vehicles that use electricity from renewable energy instead of gasoline could reduce the resulting deaths due to air pollution by 70 percent, it concluded.

Ethanol isn’t so green, either, the researchers claimed.

“It’s kind of hard to beat gasoline” for public and environmental health, said study co-author Julian Marshall, an engineering professor at the University of Minnesota.

“A lot of the technologies that we think of as being clean ... are not better than gasoline.”

The key is the source of the electricity all-electric cars need. If it comes from coal, the electric cars produce 3.6 times more soot and smog deaths than gas because of the pollution made in generating the electricity, according to the study that is published recently by the Proceedings of the National Academy of Sciences.

They also are significantly worse at heat-trapping carbon dioxide that worsens global warming, it found.

Hybrids and diesel engines are cleaner than gas, causing fewer air pollution deaths and spewing less heat-trapping gas.

电动车未必比汽油车环保

即使电动车的用电来自燃煤发电厂，开电动车的人可能依然认为他们保护了环境。但是一项新的研究表明，这种情况下他们的车实际上造成的空气污染更严重，且会加剧全球变暖。

这项颇受争议的研究提出了有关“环保”车未来的一些问题。

卡耐基科学研究所研究员肯·卡代拉说：“不幸的是，当一根线把电动车和一个燃煤发电厂连在一起时，造成的环境污染比普通的汽油车更严重。” 卡代拉并未参与这项研究，但对该研究表示赞赏。

该研究指出，驾驶可再生能源发电的电动车来取代汽油车，可以使因空气污染造成的死亡率下降70%。

研究人员表示，乙醇也不是那么环保。

研究报告撰写者之一朱利安·马歇尔表示，出于民众健康和环保的考虑，“想要取代汽油很有难度”。

朱利安是明尼苏达大学的工程学教授。

他说：“很多我们认为清洁的技术……其实不比汽油好。”

关键取决于电动车电力的来源。

最近发表在《美国国家科学院院刊》的这项研究指出，如果电来自煤，那么使用电动车产生的煤烟和烟雾造成的死亡是汽油车的3.6倍，因为燃煤发电过程产生了污染。

同时该研究发现，煤发电排放出明显更大量的温室气体二氧化碳，从而加剧了全球变暖。混合动力和柴油发电机要比汽油清洁，造成大气污染导致的死亡人数更少，温室气体的排放也更少。

Words to Learn 相关词汇

    【可再生的】

    kě zàishēng de

    renewable

    relating to a natural resource, such as solar energy, or water, that is never used up or that can be replaced by new growth

    【乙醇】yǐchún

    ethanol

    the technical name for alcohol