< p >根据Elon Musk,有“论证”,指出目前大气中的二氧化碳水平(超过400 ppm)比一些数百年前(200 ppm)。他甚至称这些低碳水平碳饥饿。< / p > < p > < a href = " https://www.youtube.com/watch?v=kzlUyrccbos&t=45m4s" rel="nofollow noreferrer">https://www.youtube.com/watch?v=kzlUyrccbos&t=45m4s What is this argument based on? What harm would it do if the level fell again to 200 ppm?