Policy Sketch and Concluding Thoughts

The purpose of this book and of Volume 1 has been to critically assess the technical potential and (where possible) the cost of achieving deep reductions in energy use through improved efficiency, on the one hand, and of rapidly deploying C-free sources of energy, on the other hand. Our focus has been on assessing the prospects of reducing CO₂ emissions rapidly enough that the atmospheric CO₂ concentration will not exceed 450ppmv. Assuming stringent reductions in emissions of other GHGs or their precursors, a CO₂ concentration of 450ppmv gives the climatic equivalent of a CO₂ doubling (from 280ppmv to 560ppmv), which, as discussed here, already poses significant risks and will entail substantial ecological and social losses. However, if CO₂ is allowed to rise above 450ppmv, the losses – both human and ecological – will be greater still.