Those who deny the importance of strong and urgent action on climate change essentially offer one of, or a combination of, the following arguments. First, there are those who deny the scientific link between human activities and global warming; most people, and the vast majority of scientists, would find that untenable given the weight of evidence. Second, there are those who, while accepting the science of anthropogenic climate change, argue that the human species is very adaptable and can make itself comfortable whatever the climatic consequences; given the scale of the outcomes that we now have to regard as possible or likely under business-as-usual (BAU), this must be regarded as reckless. Finally, there are those who accept the science of climate change and the likelihood that it will inflict heavy costs, but simply do not care much for what happens in the future beyond the next few decades; most would regard this as unethical. This paper deals primarily with the latter two arguments. An appendix addresses confusions and misconceptions about The Stern Review and responds to points made by critics in previous issues of this journal and elsewhere.