In 2016, the two presidential candidates spent all of five minutes and 27 seconds on climate change during three televised debates.

Now Democrats seeking the White House in the 2020 election are all but falling over each other with sweeping proposals for recasting the economy by promoting renewable energy, with a goal of reaching net zero carbon emissions nationally by midcentury.

The presidential hopefuls are taking cues from the Green New Deal resolution,  introduced in February by Democratic Rep. Alexandria Ocasio-Cortez of New York and Sen. Ed Markey of Massachusetts, which set a high bar for action and urgency.

To be sure, their proposal to cut greenhouse gas emissions to zero by…