  The temperature targets in the Paris Agreement cannot be met without very
rapid reduction of greenhouse gas emissions and removal of carbon dioxide from
the atmosphere. The latter requires large, perhaps prohibitively large
subsidies. The central estimate of the costs of climate policy, unrealistically
assuming least-cost implementation, is 3.8-5.6\% of GDP in 2100. The central
estimate of the benefits of climate policy, unrealistically assuming constant
vulnerability, is 2.8-3.2\% of GDP. The uncertainty about the benefits is
larger than the uncertainty about the costs. The Paris targets do not pass the
cost-benefit test unless risk aversion is high and discount rate low.
