The G20 nations couldn’t agree on the only climate goal that really matters

The dirtiest fossil fuel of all remains an ongoing problem. Environment ministers from the G20 nations met on July 23 in Italy, and although they don’t have a better plan for confronting the climate crisis, we all have a clearer view of the deep geopolitical fissures standing in the way of that goal. Chief among them: Setting a deadline to phase out the use of coal.

The idea of a deadline to phase out coal—after which rich countries would no longer burn coal in power plants or factories, or finance the construction of...