De Blasio’s suit has its heart in the right place, but it’s out of touch with reality.

With sea waters rising and coastal cities like New York in grave danger, only solipsists doubt the urgency of slowing the emissions of greenhouse gases. But only fools mistake the mirage of chasing cut-and-dried villains for anything like a solution.

Mayor de Blasio’s plan to divest city pension funds from Big Oil makes good sense — but a lawsuit he and chief city lawyer Zach Carter brought to federal court has legal logic from la-la land.

They charge BP, Chevron, ConocoPhillips, ExxonMobil and Royal Dutch Shell — the five largest publicly traded fossil fuel companies — with responsibility for the damage done in storms like Hurricane Sandy, past and future.

Follow the logic, if you can. These oil giants extracted and sold “over 11% of all the carbon and methane pollution from industrial sources that has accumulated in the atmosphere since the dawn of the Industrial Revolution.”

They also knew their products contributed mightily to what scientists recognized as global warming but downplayed those facts.

And thus bear distinct responsibility for ensuing calamity — including storms that even many fierce believers in global warming, whose mantra is that weather and climate ought not be conflated, refuse to blame directly on greenhouse gases.

Demanded compensation: many billions of dollars to cover city spending on protection against storm surge and sea rise.

The livestock sector accounts for some 15% of human-caused emissions, by UN estimate. Why, pray tell, is it spared de Blasio’s fire?

The mayor says the suit harkens to the epic cases filed years ago against Big Tobacco. But there, the industry juiced its product with addictive nicotine. Here, billions of people willingly bought and burned fuel over a century.

The man is so busy auditioning to be above-thetitle star in a courtroom drama entitled “The People Versus Corporate America,” he ignores the Bmovie script.

Meantime, this very same self-styled dragonslayer calls traffic-cutting, transit-boosting congestion pricing a tailpipe dream. Wha?

Give de Blasio this much: The first-city-in-the nation commitment to get city employees and retirees out of investments in the likes of these companies appears more than sound given Big Oil’s lousy and getting lousier market performance.

But de Blasio should have divested himself of his most outlandish crusader ambitions first.