If you’ve ever wondered why “going green” and “sustainability” have become such big issues, Mark Lynas’ book, Six Degrees: Our Future on a Hotter Planet, should definitely be on your reading list. Lynas read tens of thousands of scientific articles about global climate change and its potential consequences in preparation for writing this book. He took all of that information and broke it down by degree. Each chapter in the book lays out the likely results of an additional degree Celsius of average global temperature. The chapter on one degree of warming details changes in climate that we are already beginning to see: increases in floods in some places and droughts in others, the loss of Arctic and glacier ice, loss of biodiversity. By the time he gets to six degrees Celsius of average temperature increase, Lynas is describing a world unlike any most of us can imagine living in. This level of warming would cause plant and animal extinctions on a scale not seen since the time of the dinosaurs. This would be a world that was extremely hostile to human life, in which we would struggle to keep ourselves sheltered and fed in an increasingly chaotic environment. Lynas is optimistic about our ability to avert disaster on the six-degree scale, but only if we can control our levels of greenhouse gas emissions before we get to three degrees. At that point, we begin to reach a series of tipping points that will send the climate careening out of control and emissions cuts will no longer make any discernable difference. So, if you’ve wondered at all about why this sustainability stuff is important or what’s really at stake, I would strongly recommend that you read this book.