人类目前每年排放大约400亿吨二氧化碳，这意味着世界必须在本世纪中叶甚至更早淘汰化石燃料，并彻底转向零排放的主要能源来源。
Humanity currently emits around 40 billion tons of CO2 per year, implying that the world has only until mid-century or even sooner to phase out fossil fuels and move entirely to zero-emission sources of primary energy.