What’s the sleeper issue of the new political cycle? Here’s a good bet: It will be climate change.

The signs are proliferating rapidly. Twin wildfires in California last month have escalated public worries that climate changes are driving extreme natural calamities. While those fires burned, a new report from 13 federal agencies declared that “the impacts of climate change are already being felt in communities across the country” and predicted “more frequent and intense extreme weather and climate-related events.”

At...