On Monday, Spanish grid operators found themselves sprinting against sunset. The entire country had blacked out. Planes paused on the runway for want of air traffic control. Trains lurched to a stop on the tracks or sat in their bays at the station. Within a few hours, the Spanish government declared a national emergency.

The blackouts even reached France and Portugal. Europe is learning another painful lesson about its power sector: If one nation mismanages its grid, its neighbors suffer with it. If these blackouts were caused by Spain’s green energy policies, as seems likely, these blackouts are a preview of the world to come.