Walk the streets of Beijing and you’ll see signs of a burgeoning middle class. Everybody carries a smartphone. (Visit any tourist site and the number of selfie sticks will astound you.) Pet dogs are common; feral dogs are rare. Attire is very western, with young adults sporting jeans, plaid shirts, and synthetic jackets. Lines outside restaurants and bars indicate a disposable income that didn’t exist 20 years ago.

What you won’t see, even on a cloudless day, is the sun. That’s how bad the pollution is.

Typical Beijing scene. #nofilter

Geography is partly to blame. Situated on the leeward side of a mountain range (once a strategic spot for defense against nomadic invaders), Beijing lacks the air currents needed to circulate pollutants away. Furthermore, emissions from heavy industry in neighboring provinces blow over the mountains into Beijing and can’t escape.

But the growing population, and the growing affluence of that population, bears most of the responsibility. Beijing’s urban extent has more than quadrupled since 2000. Cars choke the streets – traffic jams on the five ring roads can last until midnight – and construction is ubiquitous. Most electricity comes from fossil fuels, and plenty of families still lack home heating and burn coal directly to keep warm. Smog is worst in the dry winter, when no rain falls to wash it away, but even in October there were days I couldn’t see 200 meters in front of me.

Ad for a respirator mask on the subway. About 10% of Beijingers wear a facemask regularly.

I’m not pointing any fingers at the Chinese; in fact, I have a lot of sympathy for them. Fossil fuels powered America’s industrial revolution 150 years ago, and provided Americans with newfound wealth and leisure time. China’s industrial revolution is still in progress, and its citizens are reaping the benefits. It seems perfectly fair that they get to use fossil fuels too. Fighting climate change needs to start with post-industrial countries, and so far we aren’t doing so hot: as of 2013 the US still emits more than twice as much CO2 per capita as China. My round-trip flight alone released about 5.4 metric tons of CO2 (15,000 miles at 0.8 pounds per passenger mile – see here), more than the average Chinese citizen generates in eight months. So who am I to judge?

Please join me tomorrow when I write about bridges in China, ancient and modern.

Bridge, pagoda, and mountains from the Summer Palace on a rare clear day.