America’s political commentary about climate change has been rather gloomy recently.

Core parts of President Joe Biden’s climate plan have crumbled in the face of Washington political realities. This month, the lack of one key Senate vote in his own party forced the president to scrap a clean electricity proposal that supporters had described as essential for lowering the country’s greenhouse gas emissions.

Now that same lawmaker, Sen. Joe Manchin of West Virginia, is reportedly opposing another climate component of the Build Back Better Act, this one involving fees on emissions of methane, a gas with even more planet-warming...