Global climate change has been our greatest market failure. Now it’s our greatest market opportunity. Market mechanisms are enormously powerful tools to apply to such challenges as climate change. Mitigating greenhouse gas emissions worldwide will require a crash program to use energy more efficiently, and to use renewable energy sources. Doing this can cut costs and drive competitiveness, spread the use of clean energy technologies that already are cost-competitive and available and develop next-generation technologies in virtually every sector of the economy.