I remember reading that there was a measurable effect attributed to the pollutants coming from China & being blown across the Philippines, if I come across it again, I'll post the link.
<edit> it was India & the Maldives
http://en.wikipedia.org/wiki/Global_dimming
- that article actually highlights the truth of Incog's 'make your mind up' point
and not enough was made of "the trend has reversed during the past decade", in my opinion