Even without restrictions, global energy consumption may peak at some point in the future, as population growth slows, poor people around the world achieve higher living standards, and our energy technologies continue to become more efficient. But for decades to come, energy use will almost certainly continue to rise around the world. Given this reality, efforts to improve energy efficiency may modestly slow the growth of energy consumption but are unlikely to halt it, much less achieve the deep declines necessary to mitigate climate change.

That Mr. Branson has developed a spacecraft that blasts humans into space more efficiently than previous vehicles is a laudable technical accomplishment. But from an environmental perspective, that accomplishment is completely overshadowed by the reality that the mogul is pioneering a new industry that involves blasting tourists into space. Should he succeed, the relative efficiency of the endeavor is almost entirely beside the point. Mr. Branson will have invented a new way for wealthy elites like Mr. DiCaprio to consume vast quantities of energy.

Weekend trips to Mars for the masses are, of course, still the stuff of science fiction. So, too, is the fantasy that climate change might be averted through deep cuts in global energy consumption.