The U.K. Royal Society has put out a nice "questions and answers" about climate change that summarizes many of the things talked about in Chapter 7 (as well as the other chapters in the book). Together with the U.S. National Academy of Sciences, they've also put out a longer report, Climate Change: Evidence & Causes, that covers much of the same ground.
Here is a video of the drinking bird, which is an analogue for internal variability of the climate system.
If you want to see the latest research on ENSO, particularly how it will change in response to climate change, Nature Climate Change has helpfully collected a bunch of papers published in Nature's journals about it. Look here.