In his chapter on climate change, he makes the point that one reason climate change skepticism is so tenacious is that the statistical data about climate patterns really is a bit on the noisy and ambiguous side. The reason you can know that the skeptics are wrong isn’t so much because the data is so overwhelmingly persuasive, it’s that the data is overwhelmingly persuasive in light of the underlying science of how greenhouse gas emissions would cause climate change. Absent the causal theory about the greenhouse effect, simply looking at a chart of world temperatures and the correlation with CO2 emissions wouldn’t prove very much. The empirical data is important because it’s in line with the predictions of a persuasive theoretical account.
It’s worth recalling that global warming was first predicted at a time when the Earth was actually cooling:
If man-made dust is unimportant as a major cause of climate change, then a strong case can be made that the present cooling trend will, within a decade or so, give way to a pronounced warming induced by carbon dioxide.