Imagine that it’s January 1941, and President Franklin D. Roosevelt is delivering his annual State of the Union address to a joint session of Congress. The planet is literally on fire from the Big One, World War II. Nazi Germany has overrun France, and Adolf Hitler’s regime has been raining bombs on London for months. Japan has overrun much of Asia.

But FDR begins his speech with a long riff on how great the American economy has done under his presidency — including some gratuitous swipes at his predecessor Herbert Hoover, even though it’s been eight years since Hoover left the Oval Office. There’s a brief, bloodless mention that “our relationship with our European allies has never been stronger," and then he moves on — urging a standing ovation for the oldest living veteran of the Civil War. And when the speech is done, the radio pundits gloss over Roosevelt’s snub of the global conflagration.

That’s too crazy to contemplate, so then how insane was it that President Trump rambled on for one hour and 18 minutes (and four seconds) last Tuesday in his reality-show-influenced 2020 State of the Union address and ignored the cataclysmic fires that have engulfed Australia and echoed the flames that are ravaging California year after year, let alone the increasing scientific evidence that we’ve entered a time of rapid sea rise, drought and killer storms?

» READ MORE: Oilman David Koch set the world on fire, then died and left us to face the rising flames | Will Bunch

How could the leader of a global superpower give a serious talk on the current state of his nation in 2020 and never once utter the words “climate change”?

And how did so few people even notice? Delivered just hours before his impeachment trial ended in acquittal, Trump’s third State of the Union summoned up a whirlwind of distracting pop-culture headlines — awarding the Presidential Medal of Freedom to cancer-stricken hatemonger Rush Limbaugh to own the libs! — and a now-predictable blizzard of lies, including a false narrative about a black Philadelphia schoolgirl that was exposed by my Inquirer colleagues.

Amid that 130-decibel assault of political noise, the planet’s actual crisis of climate change became the equivalent of Sherlock Holmes’ most famous clue, the dog that didn’t bark. Centuries from now, when Rush Limbaugh’s hate words have drifted off to space and his name is long forgotten, scholars — if there still are scholars — will find that Trump’s stunning denial of science and a raging crisis was this speech’s only historical significance.

The president occasionally tries to deny being a “climate denier,” but Tuesday’s silence was deafening. Especially when Trump did take time to brag that America under his so-called leadership is pouring fossil fuels on the world’s fires. “Thanks to our bold regulatory reduction campaign, the United States has become the No. 1 producer of oil and natural gas anywhere in the world, by far,” he declared to thunderous applause.

That truth — hardly comforting in a time when oil and natural gas are the major sources of greenhouse-gas pollution — was typically followed by Trumpian distortions. If the U.S. is “energy independent,” then why do we continue to import about 10 million barrels of oil every day, much of it from murderous dictatorships? If our interest in fuel production is job creation, why does Team Trump ignore the employment power of clean energy?

But those deceptions pale in comparison to the biggest problem — that the American president is bragging about its oil-and-gas growth when scientists are predicting planetary catastrophe without major cutbacks by 2030 in fossil fuels, and near elimination in the generation after that.

Trump’s ode to climate denial came just before the news that Antarctica — with its massive glaciers that could swamp the low-lying areas where 40 percent of Americans (and billions elsewhere) live — posted its warmest day in history, 65 degrees. This followed a report that one of Antarctica’s largest glaciers, the size of the state of Florida, is melting much faster than earlier predicted, with a potential to sharply increase projections of sea level rise.

But you don’t have to travel to the South Pole to see climate change. I can just look in my back yard here in suburban Philadelphia, where snowdrops and other spring plants are blooming after January was nearly six degrees warmer than normal. Ditto for Europe, which just experienced its hottest January on record.

And yet, of course, President Trump dared not mention any of this, because viewers might question why his administration keeps making it easier to burn coal or drill for oil — both as a sop to his full embrace of oil-and-gas lobbyists and their money, and because undoing all things Obama is catnip to his base. (Although worth noting is that Obama also hailed rising oil-and-gas production, and history will also not remember that kindly, either.)

Team Trump is betting that 2020 voters will only care about low gas prices at the pump. But that’s only true if you talk only to the typical Fox News viewer, a white person over 50. Ask most Americans currently under 35 — a voting bloc that gets bigger by the day — and they’ll say climate change is their No. 1 issue. (And among all Democrats, it ranks No. 2 behind only health care.) Trust me, these voters heard the dog that didn’t bark on Tuesday.

This weekend, Salon’s Amanda Marcotte, reporting from the final frantic days of the New Hampshire primary, found a thirsting among voters — especially, but not exclusively, younger ones — to hear even more from the Democrats about what they will do to roll back four years of devastating climate denial from Trump.

Marcotte noted that at an Elizabeth Warren event, her biggest applause moment came from a seemingly arcane question about the Granite State’s endangered moose population, because it teed up a stirring defense of the Green New Deal. She also hung out with a group of mostly under-25 protesters outside Friday’s ABC News debate who are mad there’s been such little discussion of climate. Said 19-year-old Kyle Burzycki: “It’s embarrassing how little they’re talking about it, seeing as it’s the most important issue facing our country.”

» READ MORE: These Philly schoolkids are striking Friday because ‘grown-ups’ have failed them on climate | Will Bunch

The so-called grown-ups don’t seem to be receiving the message. The one ABC debate question on climate came late, and it came with the how-are-you-going-to-pay-for-it baby boomer skepticism that continues to alienate under-35 voters. The Democratic National Committee — which nixed a plan for a climate-only debate and reversed itself on taking fossil-fuel donations — hasn’t helped, either. The party seems to have learned little from 2016, when young-voter defections to the Green Party’s Jill Stein helped elect Trump.

Many Democratic voters are demoralized right now by Trump’s acquittal, the triumphalism of his base, and the inept chaos of their own party’s Iowa caucus. And while there are significant differences between the Democrats — only Warren and Sanders have fully embraced the urgency of the scientific warnings — everyone still in the race would represent an 180-degree reversal from the cynical denialism of Trump. If the party wants to win in November, it’s time to wave that banner higher, shout a little louder, and make sure that Tuesday night was America’s last State of the Union address to pretend that climate change is not real.