The American teacher and environmentalist Bill McKibben is one of the most convincing writers around on the topic of global warming. He has just published an article in Rolling Stone magazine in which he talks about “three numbers that add up to global catastrophe.” Let’s follow him through those numbers but a couple of preliminary points before we do.

Global warming occurs when carbon dioxide and other gases pumped into the atmosphere heat up the planet as a by-product of our burning fossil fuels. There is by now a growing and near overwhelming scientific consensus about this reality. There are to be sure those who continue to deny the science, much as some people still deny that the handling of asbestos causes cancer.  Some of them are sincere but frequently the claims are made by or on behalf of industries that profit from business as usual.