In its new report on the risks from human-caused climate change, the American Association for the Advancement of Science (AAAS) sets climate science back rather than “advancing” it. The report, counterfactually titled “What We Know,” is more an account of what the scientific community thought it knew about a decade ago than an up-to-date telling of current understanding. Not surprisingly, the group ignores the fact that climate science is moving in a direction that increasingly suggests that the risk of extreme climate change is lower than has been previously assessed. Instead, the AAAS continues to play up the chance of...