所报告的全球变暖成本比早先的研究中提出的要高，那是因为它将越来越多的新证据考虑在内，比如全球变暖是一个高度复杂且非线性的过程。 一种不可忽视的可能性是它发生的速度比我们先前想象的要快，而且变暖的程度也比我们先前想象的要高。
The reported costs of global warming are higher than in earlier studies because it takes into account the mounting evidence that the process of global warming is highly complex and non-linear, with a non-negligible chance that it may proceed much faster than had previously been thought and that the extent of warming may be much greater than had previously been thought.