Historical data for Beijing in 2011 is available at young-0.com/airquality . I don't have any other cities that far back.
Here is an update for people interested in historical data. I found a site stateair.net that has Beijing historical data as far back as 2008, and imported it into my site young-0.com/airquality . There is also historical data for the other cities, though not as far back.
Someone showed me where some other city information was available, so I added Chengdu, Guangzhou, Shanghai, and Shenyang to the db at http://young-0.com/airquality . Information for each is available for about the last year. Currently the other cities are not updating hourly like Beijing is, I haven't had time to do that yet, but they do have the historical data, and I'll update them every few days until I get the automatic updating written.
I wrote an application that runs a cron job every hour to save the data for Beijing,
http://young-0.com/airquality If I can get a good feed for other sites in Beijing I would add those as well. Is there an rss feed where the data is available? Parsing it from the webpage is too fragile.
The source code is available there if anyone wants to set up their web server for other cities.rwy supported this idea ·