Could what is available add up to a ‘solution’? but only with Known technologies could in principle meet demand with constrained CO 2 (but > 500 ppm inevitable?) until the middle of the century, but only with technology development, e.g. for carbon capture and storage - essential increased efficiency: most obvious steps save money – why’s it not happening? all known low carbon sources pushed to the limit (including much more nuclear) public willingness to pay more before the lights to out in order to reduce CO 2 and prevent lights going out, and/or political will globally to force the public to do so → cost up through Carbon tax (best) or credits (more likely) + strong regulations After fossil fuels depleted, must continue to use everything available. But there will be a major gap without big contributions from Solar (need cost down + storage), and /or Nuclear fission (→ thorium if feasible + fast breeders in the very long run), and/or Fusion (must be developed) Malthusian solution if we fail?

Savings from Improved Efficiency  2007 McKinsey study claims USA could save 20% of its CO 2 emissions (5.7 Gt/year) through measures all of which save money (50% by overall cost neutral measures)  IEA 2006 Alternative Scenario (‘only’ +30% CO 2 in 2030 compared to +50% in Reference Scenario) To 2030: $3 trillion less investment on supply side $2.4 trillion more investment on demand side → $8.1 trillion saving in power bills (pay back times ~ 3 years in OECD/1.5 years developing countries) Gains biggest in developing world ‘low hanging fruit’; demand side work cheaper but implementation requires many individual investment decisions, by people - such as landlords, developers who won’t be paying the power bills - in the developing world, without access to capital - in developed world, without a great interest in individually small savings