Are economists getting climate dynamics right and does it matter?

We show that economic models of climate change produce climate dynamics inconsistent with current climate science models: (i) the delay between CO2 emissions and warming is much too long and (ii) positive carbon cycle feedbacks are mostly absent. These inconsistencies lead to biased economic policy advice. Controlling for how the economy is represented, different climate models result in significantly different optimal CO2 emissions. A long delay between emissions and warming leads to optimal carbon prices that are too low and attaches too much importance to the discount rate. Similarly we find that omitting positive carbon cycle feedbacks leads to optimal carbon prices that are too low. We conclude that it is important for policy purposes to bring economic models in line with the state of the art in climate science, and we make practical suggestions for how to do so.