Well, this is depressing. I thought the pollution has markedly improved in Chengdu in recent months. It felt much worse in the spring.
Such data is about as worthless as it gets, since there is no info about what exactly is being measured. Doesn’t make Chengdu any safer or cleaner though.
I don’t think this is true – judging the air quality by the appearance of the sky would be worthless. AQI is a legitimate way to simplify and communicate the complexities of air quality to laypeople. It’s factored by collecting ground-level ozone, particulates, sulfur dioxide, carbon monoxide and nitrogen dioxide.