Sometime in the mid 1970s my father bought a sign that said “Thank You for Not Smoking,” which he put on a shelf in his living room.

In those days, people would pull out a cigarette and light up without asking permission or even looking to see if there was an ashtray around. My father told people that he was “allergic” to tobacco but I think he was just a former smoker who hated the way it smelled.

That’s a perfectly normal view today, but in those days it was considered rude, so he felt the need to invent a medical reason and post a passive aggressive no-smoking sign in his own home.

Things are different now. The few smokers I know don’t even light up in their own homes, let alone my house. They go outside to smoke in all weather and are apologetic about even that.

It used to be one way and now it’s not. What changed? The culture.

The late Andrew Breitbart, the right-wing activist and journalist, famously said “Politics is downstream of culture.”

I understand that to mean candidates who win elections are the ones who best represent the values of their voters. And once they are in office, their understanding of those values guide the decisions they make. It’s not the politicians’ ideas that drive change, but their ability to navigate the currents of culture.

Which is tricky, because culture changes. It’s not just smoking. The biggest turnaround in my lifetime has been public opinion on same-sex marriage, which went from being a highly controversial idea in the early 2000’s to a no-big-deal national consensus today.

Not everyone is onboard, of course: Some people still smoke, too. But you can see from the near-miss presidential candidacy of Pete Buttigieg – a married, gay man – something has changed.

What makes the world shift like that and when will the culture come around to the reality of climate change?

It’s not a matter of information. The most respected authorities release reports every few months that document the kinds of existential threat we are facing. Best case scenarios predict much increased coastal flooding, droughts, wildfires, severe storms and maybe a billion refugees in the next few decades.

All the experts agree that we need to turn the world’s economy on a dime to get off fossil fuels to avoid much worse outcomes. But public complacency makes that kind of effort unimaginable.

I’m not just talking about the climate change deniers, who make ignoring science part of their identity and wear their ignorance as a badge of honor.

But a bigger problem is the reasonable majority who read the headlines, say they are concerned and then jump behind the wheel of a car or truck and drive solo to work, never considering that their choices a billion times over are making the planet uninhabitable.

In Maine, transportation makes up 40 percent of our carbon emissions. It could be zero if that’s what we wanted, but apparently we don’t. As a society we drive more miles every year as if we weren’t running out of time.

The situation is a little like cigarette smoking 50 years ago. The scientists told people that it was bad for them, but the culture told them that it was really OK.

There is no shame to wasting fossil fuel to get around as long as almost everyone else is doing it. There is no social pressure to drive less, share rides or even quit the driving habit for good.

We don’t have 50 years to figure this out, but cultural change can happen quickly. Last week I thought that a tough-guy workplace culture that expected people to show up when they are sick would make it hard to stop the spread of coronavirus.

This week, someone blowing their nose in the office would get about the same reaction as someone who lit up a cigar. We are going to see what a presidential campaign looks like without rallies, baby kissing or handshaking, and who knows if those social conventions will ever come back.

In the meantime, I’ll remember my father and say, “thank you for not driving.”