人类的行为 — — 燃烧化石燃料 — — 已经将二氧化碳浓度提高到50万年来最高的水平，而且还在以每年约0.5%的速度上升。
Human actions – burning fossil fuels – have already raised the carbon dioxide concentration higher than it has ever been in the last 500,000 years, and it is rising by about 0.5 % a year.