Let’s restate more accurately a plan recently announced by Thomas Steyer, a California hedge-fund billionaire whose idea is to make the coming midterms about climate change: He would spend $100 million to flog an issue voters don’t care about, to defeat Republicans whose defeat would have no impact on climate change, in order to replace them with Democrats whose election would have no impact on climate change.

Mr. Steyer’s thinking is puzzling unless his goal is to make $100 million disappear. If his purpose were to elect Democrats, wouldn’t his money go further attacking Republicans on matters of interest to voters? If he wants to move the ball on climate change, wouldn’t a better place to start be undoing the damage his fellow climate lobbyists have done to the cause with their hysterical exaggerations, false statements and moral bullying?

He could begin by running ads leveling with Americans about climate science. We know with comfortable certainty that human industry is adding to carbon dioxide, a so-called greenhouse gas, in the atmosphere. An insoluble noise-to-signal problem, though, is how much the human component may have influenced climate change already. And forecasts of future warming depend on theoretical models that are highly speculative and necessarily suspect.

Then there’s the political problem: Nothing America could do by itself would make a significant difference.