— President Trump on withdrawing the United States from the Paris climate accords.

The year was 1946, and the newly elected mayor of Pittsburgh, David Lawrence, saw that his city had a big problem. To the extent that he could see anything. The many steel mills and industrial outposts that lined the Monongahela, the Allegheny and the Ohio Rivers had been running full blast to power the war effort, and now the booming post-war economy. Grey, sooty smoke cascaded down the main boulevards and blocked out the sun at high noon, forcing the city's neon-lit business district to go electric all day. (You can see some of the remarkable pictures here if you don't believe it.) For decades, even the city's doctors had insisted that a little smog was good for you, but with lung diseases on the rise, no one believed that anymore

"I am convinced that our people want clean air," Lawrence said in his inaugural address. "There is no other single thing which will so dramatically improve the appearance, the health, the pride, the spirit of the city." His anti-pollution push gained speed after a famed 1948 incident in the southwestern Pennsylvania town of Donora when a smog inversion killed 20 people. Over the next decade, smoke pollution in Pittsburgh decreased by 90 percent, and layers of soot were scrubbed from the city's buildings. The notion that dirty air doesn't make for a successful city came in handy a generation later when steel and associated industries collapsed. While some corners of the Rust Belt have fared quite badly, Pittsburgh has survived and arguably thrived as a center of health care and, yes, clean energy research.

David Lawrence got that. So does Bill Peduto, who's the current mayor of Pittsburgh and who said just minutes after Trump cited his concern for the citizens of the Steel City that "we will follow the guidelines of the Paris Agreement for our people, our economy & future." (So did Philadelphia's Mayor Kenney, who like scores of other mayors and local leaders has vowed to reduce carbon pollution regardless of the callous indifference in Trump's Washington.) Donald Trump is a dangerous ignoramus, whose only justification for a policy that poses serious and unacceptable risks for our children and grandchildren is a) he's doing the opposite of whatever Barack Obama did and b) his insane nationalist advisers like Steve Bannon (who never really lost clout after all) are convinced this plays well with that certain sector of the electorate that hates "pointy-headed" scientists, etc.

This is a dark day for the planet — darker than the streets of Pittsburgh at high noon in 1946. The president of the United States — in a job that many once called "the leader of the free world," hard as that is to believe now — rejecting the best science on our climate is both the logical conclusion of 50 years of GOP know-nothingism and a moment where it's not at all trite to say that common sense has been trumped by evil self-interest.

Carbon pollution nearly strangled Pittsburgh once. Today, Donald Trump's phony concern for that city was actually another death threat — one that is more complicated yet also more insidious. But this much is certain: Dirty air, drought and rising sea levels are unaware of national boundaries. Citizens of Pittsburgh, Paris, Philadelphia, and Pretoria are all riding in the same leaky boat. It's time for Captain Queeg at 1600 Pennsylvania Avenue to move away from the big wheel and let America's cities, our states, and our true friends around the globe try to steer us to safe harbor.