India, Sept. 19 -- Most evenings in summer, the grid groans. Fans run harder, water pumps work longer, and the furnaces that smelt our steel never stop. Much as we would like to believe this is a story increasingly powered by solar parks in Rajasthan and wind farms in Gujarat because India has built significant capacities, the truth is less flattering. When demand peaks, it is coal that saves us.

Last week, the mandarins in Delhi offered a fix. Huge subsidies to trap the smoke from coal before it hits the air. A promise that we can keep burning the black rock and still call it clean. This sounds clever. But here's the problem. It isn't new. Norway tried. America spent billions. China is still at it. None have cracked the code so far.

Th...