The lede of the day was written by Andrew Jacobs of the New York Times, who grabbed my attention with this first sentence:
A noxious cocktail of soot, smog and toxic chemicals is blotting out the sun, fouling the lungs of millions of people and altering weather patterns in large parts of Asia, according to a report released Thursday by the United Nations.
Interstingly, the report (pdf), put together by the United Nations Environment Program, says that the "atmospheric brown clouds" (ABCs) could be mitigating the impact of climate change on a global basis by as much as 80 percent, though they are in some places amplifying the impacts of greenhouse gases and on the whole are a Very Bad Thing.
Below is a graphic showing different "plumes" where the brown clouds peaked at different times of the year from 2001 to 2003:
The report names 13 "mega-city ABC hotspots": Bangkok, Beijing, Cairo, Dhaka, Karachi (sorry, guys), Kolkata, Lagos, Mumbai, New Delhi, Seoul, Shanghai, Shenzhen, and Tehran.
Having lived in Cairo for about a year and a half, I can testify that the air there is simply awful. I used to start coughing as my plane was landing at the airport outside of town, if only out of habit.
(Hat tip: Matt Yglesias)