Climate change is an existential threat to the United States of America and to humanity as a whole, and time is running very short to undertake the necessary top-to-bottom overhaul of world society to stave it off. That is why Democrats must become the party of fervent climate radicalism — there simply is no alternative. Especially not with President-elect Trump, who just announced he is going to appoint Oklahoma Attorney General Scott Pruitt as head of the EPA — a man who was caught by The New York Times sending oil company-written complaints to the EPA on his own letterhead.

This presents a political difficulty. Unlike previous existential threats — like Nazi Germany, for example — the really serious danger of climate change is far in the future, it will gather strength relatively slowly, and, above all, knowledge of it comes through a highly technical and abstract scientific process. "Armed men will invade and kill us all" is easy to understand and culturally familiar; "in 50 to 100 years climate feedbacks could spin out of control and do irreparable damage to the biosphere which supports human life" is not.

Nevertheless, it will be possible for Democrats and the left to thread this needle, if they can maintain their focus. Any unaddressed existential threat almost must be a political opportunity — it's simply a stiff problem of political ideology, communication, and organizing.

First of all, Democrats must purge themselves of centrist hesitation on climate policy. Climate change, for a variety of historical reasons, was originally coded as an environmental issue. For the centrists in D.C., that means dirty hippies laying down in front of bulldozers to protect endangered screech owls or something. Small, unimportant, quaint little issues for soft-minded liberals who compost and donate to NPR — as opposed to big, important stuff like jobs, cutting Social Security and Medicare, or invading random countries for no reason. (That's why climate change did not get a single question in the 2016 presidential debates.)

In reality, of course, climate change is the single most important issue in politics — and one which Republicans deny is happening. That makes political centrists, who tend to bend their analysis around their unshakable conviction that the best way forward always lies square in the middle of the political spectrum, all but useless on climate change. Really dim ones, like Josh Kraushaar, can write an entire article arguing that Democrats need to dial back their (already feeble) climate policy without once mentioning that climate change will cause, you know, tremendous problems.

But many Democrats have a similar attitude. Hillary Clinton, had she won, was likely to have Jake Sullivan as national security adviser — a Yale-educated man who was totally unfamiliar with the most basic facts of climate policy. It's like hiring a secretary of agriculture who has never heard of corn.

Even more common among Democrats is paying lip service to climate change while taking steps to undermine climate policy. No less than President Obama gestures to the threat of climate change, and takes some partial steps to address it — while enabling the fracking boom and boasting about the number of pipelines built under his administration.

Once they rid themselves of this unhelpful rhetoric, Democrats and the left must start educating. Sixty-eight percent of Democrats (and 41 percent of independents) agree that climate change is a "very serious problem." The major task for the left over the next several years is to put some force behind that belief — to convince people that it is a first-rank political problem that deserves the absolute maximum level of policy aggressiveness.

In this they must beware of unscrupulous nitpicks. Climate science and policy is reasonably straightforward in broad outline — greenhouse gases trap heat, which will cause many bad things, therefore greenhouse emissions should be curtailed — but like any technical subject, it has many wrinkles and caveats in fine detail. Deniers and what I call climate trolls seize on any arguable slight technical inaccuracy or over-generalization — or take statements out of context to create the appearance of same — to puff up their own reputations as the defenders of science against hysterical environmentalists. (The most obnoxious of such trolls, political scientist Roger Pielke Jr., recently wrote an article in The Wall Street Journal lamenting actual climate scientists' baffling habit of getting really mad when he repeatedly accuses them of scientific malpractice.)

Fortunately, with a bit of practice such people are easily recognized, and rely above all on a Zerg rush of irrelevant detail. Simply returning discussion to basic facts (carbon dioxide bad, must stop emissions) is about all that one needs.

Finally, Democrats and the left must help, support, and join with climate activists. People like the ones fighting the Dakota Access pipeline (a permit for which was recently denied by the Army Corps of Engineers) are desperately needed to provide on-the-ground political force against the power of Big Carbon. These efforts must be nurtured, supported, and encouraged wherever possible.

Climate news is going to be very, very bad under President Trump — indeed, it's really bad now. With a bit of effort, it ought to be easily possible to make some political hay out of the fact that he is handing the climate policy reins over to people who would chance the destruction of the United States for the sake of a few more years of carbon company profits.