[kurthr]

You can't even fairly compare LA in the 80s (where I lived) to Beijing (or Hebei) today, much less the "smogless" wonderland that is the valley of today. The winter smog (ignoring outliers like CNY or political events) is worse than you can imagine. Typical PM2.5 is in the hundreds... a bad day in the week might be 500, and once a year they break the instruments with 900+ measurements.

[miketery]

I can't infer whether 80s LA was worse or better than Beijing today from your comment.

[kurthr]

Sorry for the confusion, on the worst single day of smog I observed in Pasadena during the early 80s, the visibility was about as bad some 5-10 days I have observed in Beijing and multiple other cities in the last 2-3 years. It's not getting better, and it is so much worse than it was 15 years ago!

I thought it was getting better in China this year... I really did, but then winter came and you could barely see across the street at midday. Southern California meanwhile went from months of missing mountains to a day or two here and there during the summer over the course of 10 years as catalytic converters became standard.