If, as many scientists believe, life can readily emerge under the right environmental conditions, it is possible that life arose on Earth more than once.

如果，如许多科学家所相信的那样，生命能够在适当的环境条件下迅速出现的话，很可能地球上不再只一次出现生命。

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This would be a great advantage because, as most scientists agree, burning fossil fuels is the main cause of environmental problems such as acid rain and global warming.

诚如大多数科学家所言，利用好太阳能相当有益，燃烧化石燃料是导致酸雨和全球变暖等环境问题的首要因素。

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Some scientists and environmental groups promote 350 ppm as a safe level for CO2, but scientists acknowledge they don't really know what levels would stop the effects of global warming.

NPR: Experts: CO2 Record Illustrates 'Scary' Trend

Some scientists and environmental groups promote 350 parts per million as a safe level for CO2, but scientists acknowledge they don't really know what levels would stop the effects of global warming.

NPR: Greenhouse Gas Milestone; CO2 Levels Set Record

Begun in 1996 as a body to coordinate Arctic policy, the council was for many years seen as a platform for scientists to swap research on environmental issues.

WSJ: Arctic Body Weighs China's Bid to Observe