工廠冒出的煙霧 (Gōngchǎng mào chū de yānwù)
smoke from factories
全球暖化 (Quánqiú nuǎn huà)
Global warming
汽車冒煙 (Qìchē mào yān)
smoke from cars
砍伐森林 (Kǎnfá sēnlín)
deforestation
溫室效應 (Wēnshì xiàoyìng)
Greenhouse effect