The advocates of a US federal carbon tax are in an awkward position. They have stressed to the public that the majority of natural scientists believe human-caused carbon emissions are at least partially responsible for the rise in global temperatures over the last century, and that any physicist or climatologist who denies this is outside “the consensus.” They think this is sufficient to prove that a US carbon tax is therefore a wise policy move. Unfortunately for them, “the consensus” in the economics literature shows that this conclusion is far more dubious.