The economic advice on climate policy is simple. Greenhouse gas emissions are best reduced by a carbon, a uniform carbon tax, and nothing but a carbon tax. Model studies show that a gradual path towards full decarbonization would only slightly reduce economic growth. The welfare impact of missing political climate targets is probably small too. However, it is no one’s interest to keep climate policy simple. Bureaucrats like to expand bureaucracies, politicians like to grandstand and create rents for allies and voters, environmentalists need to exaggerate to maintain fees and influence, creating room for opponents to polarize and block. After spending 15 years on trying to negotiate an infeasible international treaty, the Lima-Paris Agreement at last adopted the pledge-and-review architecture recommended by game theorists. International climate policy faces three major challenges after the 2021 Conference of the Parties in Glasgow. First, the current geopolitical situation is not conducive to international cooperation. Second, it is increasingly apparent that emission reduction pledges will be missed, while these pledges are known to be insufficient to meet the agreed climate goals. Third, the disaster foretold for crossing 1.5°C global warming will not come to pass. This implies another fundamental reset of international climate policy in the next decade, centered around more realistic goals and focussed on research, development, deployment and diffusion.