These corrected climate predictions raise a crucial question: Why should people world-wide pay drastic costs to cut emissions when the global temperature is acting as if those cuts have already been made?

On the 30th anniversary of Mr. Hansen’s galvanizing testimony, it’s time to acknowledge that the rapid warming he predicted isn’t happening. Climate researchers and policy makers should adopt the more modest forecasts that are consistent with observed temperatures.

That would be a lukewarm policy, consistent with a lukewarming planet.