After a tsunami triggered a meltdown at the Fukushima No. 1 nuclear power plant in 2011, the world¡¯s third- and fourth-largest exporters decided on radical changes to their energy policies. Both agreed that a break was needed from the grids of the past. In every other way, the approaches couldn¡¯t have been more different.

Japan shut down its nuclear sector almost immediately and made up most of the difference by burning more coal. Germany announced a slower nuclear phaseout, along with support for the nascent wind and solar industries. Twelve years later, the differences are stark.

In Germany, a renewables boom pushed the zero carbon share of energy generation to 58% last year. Emissions per capita fell 21% relative to their 2010 level, even as real gross domestic product rose about 14% per person.