All this dirty air makes me hopeful.

It's often argued that climate change is too slow, too insidious, for humans to take much notice and actually act. Not so when it comes to smog. And as it becomes increasingly clear that smog is having huge economic consequences in cities across the Globe, we can expect the efforts to tackle air quality issues to give very real, substantial impetus to cutting carbon emissions too.

Just take these few examples:

Last year, Paris temporarily banned 50% of cars from its roads and made public transport free. Almost exactly a year later, it is doing the exact same thing again as air pollution spikes to dangerous levels once more. Not only are there significant direct health impacts of such appalling air quality, but between the damage to tourism and the economic costs of banning cars and making buses and trains free, it's not hard to see that the status quo is untenable. (That's why the mayor wants more long-term action.)

The Guardian also reports that the smog from Europe has carried over to the UK too (that happened last year as well). Meanwhile a recent London bus strike showed how quickly air pollution comes down when you don't burn as much dirty fuel, as long as you can persuade your neighbors to stop burning it too.

And over in China, as a documentary about air pollution goes insanely viral, the country is slashing coal use, shuttering power stations, and the country's Ministry of Transportation has just announced ambitious targets of getting 300,000 alternative fuel buses and taxis (many of them electric) on the road by 2020.

The exciting news is that the tools we need to cut smog and carbon emissions are already here, and they are getting increasing attention from the world's cities. Whether it's bike highways, electric buses, urban forestry, distributed clean energy or radical energy efficiency, as each new project rolls out, there are fewer and fewer excuses for cities not to act.

It sucks that we all have to breathe this dirty air, especially when people are dying, but the alternative could be even worse. When you can't breathe, you have little choice but to act.

Meanwhile, in The Guardian's reporting of Paris' latest smog crisis, I was drawn to this brief quote from Rosa, a concierge sweeping the front of a building near Boulevard Saint Martin as the emergency measures kicked in and the streets were emptied of cars:

“I can breathe.”

Would that we were all so lucky. And just in case you don't think there's anything we can do about it, take a look at Pittsburgh in the 1940s before air quality laws took effect. (Now imagine if they'd had electric buses, teslas and solar panels back then too...)