shots look smoggy?

[kevin99989]

I was at 200mm zoom, and took this around sunset in cold weather. The air seemed clear to my eye (no smog) when I took this shot of the city about 8km away. Yet i had to increase the contrast somewhat (already done in this image) to remove the smoggy appearance.

Has anyone else experienced this kind of thing, especially when taking shots over a distance, where the image capture by your camera is more hazy than what you see.

I used my UV filter in this shot too, even though the sun was setting.