We use the Euler equation to put forward a back-on-the-envelope rule for the global carbon tax based on a two-box carbon cycle with temperature lag, and a constant elasticity of marginal damages with respect to GDP. This tax falls with time impatience and intergenerational inequality aversion...

Climate change must deal with two market failures, global warming and learning by doing in renewable use. The social optimum requires an aggressive renewables subsidy in the near term and a gradually rising carbon tax which falls in long run. As a result, more renewables are used relative to...