While many scientists once thought that only lighter greenhouse gases,such as carbon dioxide,could travel across the Earth,they now say that aerosol clouds can too.

• 从前许多科学家认为只有那些较轻的能够引起温室效应的气体，例如二氧化碳，才能够围绕地球游动，但是现在看来带有悬浮颗粒的烟雾也是可以的。