One of the problems of trying to figure out how healthy the Earth is, is that we have -- you know, we don't have good weather data from 60 years ago, much less data on things like the ozone layer.
想要测出地球健康程度的一个麻烦在于 ——从60年前开始我们就没有好的气像数据。 其他事物例如臭氧层的数据更是少之又少。