I think what Klaus is saying is that the money you'd spend on mitigation today can be best invested to obtain high [higher than Stern's assumed discount rate] long-term returns and the proceeds used to pay for reparation of any damage, at a profit [the profit coming from the difference between the yield of your investment and Stern's discount rate].

What is Stern's discount rate, and how does that compare to projections of real GDP growth?

Can the last politician to go out the revolving door please turn the lights off?