GLOBAL WARMING has not taken a break since the covid-19 outbreak struck. The Democrats, at least, are treating it like the emergency it remains.

House Democrats released late last month a massive climate plan, a package of bills that Speaker Nancy Pelosi (Calif.) has vowed to advance through her chamber. Meanwhile, a committee that presumptive Democratic presidential nominee Joe Biden and primary rival Sen. Bernie Sanders (I-Vt.) convened to reconcile their views on climate policy has agreed on some top-line principles. If the Democrats win big in November, they would have a shelf fully stocked with pre-written climate policies from which to choose. That alone puts them far ahead of Republicans.

Still, the House’s very detailed plan is a huge policy grab bag that would require refinement if it were close to becoming law, and Mr. Biden should be thinking now about how to winnow it down — and how to avoid promising too much to fringe activists during the campaign.

House Democrats propose requiring that all electricity come from clean sources by 2040, by imposing a national clean-electricity mandate that would require utilities to derive a steadily rising percentage of electricity from renewables or emissions-free nuclear power. The plan calls for regulations and spending to require electric vehicles, promote super-efficient buildings, plug leaks in the nation’s gas infrastructure and directly finance further deployment of renewables.

Curiously, the plan also proposes putting a price on greenhouse emissions, presumably through a carbon tax or a cap-and-trade program, which would accomplish many of the same environmental goals that other policies in the plan are designed to tackle, but at a far lower cost. Where that is the case, duplicative policies should be removed.

It is not clear this will happen. Though pricing carbon dioxide is the best idea, it is buried deep in the report, in a section that contains far less detail than those promising new government mandates or spending. Mr. Biden himself similarly played down pricing carbon in the climate plan he released during his primary race. If Republicans were engaged, they could push for market-based policies such as carbon taxes and against unneeded mandates and spending. Instead, they have largely exiled themselves from the debate by refusing to accept the necessity to act vigorously. The result is a conversation largely about how far left climate policy should go, rather than how to make it more appealing to the center.

To be clear, Democrats deserve credit for listening to scientists on the level of ambition needed, and they have not surrendered to the left flank of the debate, refusing, for example, to strike nuclear power from the conversation. Moreover, the threat of climate change is so large that even second-best policies are better than nothing. But should he have the chance to govern, Mr. Biden should still aim higher than second-best.

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