For 20 years the world has tried subsidizing green technology instead of focusing on making it more efficient. Today Spain spends about 1% of GDP throwing money at green energy such as solar and wind power. The $11 billion a year is more than Spain spends on higher education.

At the end of the century, with current commitments, these Spanish efforts will have delayed the impact of global warming by roughly 61 hours, according to the estimates of Yale University's well-regarded Dynamic Integrated Climate-Economy model. Hundreds...