To "delete" or not to "delete"

jus2shy wrote:
Just wanted to add... this is what happens if we just let everyone delete. This is normal pollution levels in Beijing. I've seen pictures of Portland, Seattle, Tacoma, and all other places in the PNW from the 60's and 70's, and they looked just the same.

Reuters

While it is true that in the 1980's and earlier you could not see some of the mountains in the LA basin from the bottom of the valleys, the smog was due to the trapping of ALL vehicle emissions by an inversion layer.

It was not proven to actually be due to the vehicles themselves, but more due to the atmospheric effect. An inversion layer forms when hot air just sits above a colder layer of air next to the ground, and traps all polluted air.

So, which set of vehicles caused the pollution. Gas cars, diesel trucks, or was it local industry, or was it just dust?

Nobody really knows the answer to that question. It did get better, was it vehicle standards, general air quality standards and restrictions on industrial emissions? Changing plane flight patterns (planes put out emissions also), or was it the reduction in cow methane put out by decreasing farm land usage?

Nobody really knows the answer to these questions still. It could have been a cumulative effect of many factors.

As for Beijing, most of the pollution is actually wind driven dust from the northwest winds bringing fine dust particles from the Gobi desert, which scatters light. There is some pollution from motor vehicles, but there are also lax industrial emissions standards as well.

There is no single cause, there are no easy answers. I did my thesis on some of this stuff and studied it for many years.