It actually says as much in the article linked by grand parent, but I also remember reading about it a few years ago in china daily or globaltimes (probably the latter), so it has been brought up in the Chinese press as well. Anecdotally as well: I was living in Beijing during the entire time period and noticed the dust storms going away and then coming back.

Fun story: Beijing kids are all required to plant trees on school organized trips (which they must also pay to plant). So they go to places in the hinterland that are designated for tree planting, and plant their trees. After each school group leaves, the trees are promptly dug out so they can be planted by the next group of kids.