Lens distortion in one of the desert scenes...

Did anybody notice, particularly around the 70 minute mark, where Charlie (Jack) is chasing the black van in the desert, followed by the on foot chase, that most of those shots have a weird distorted appearance to them? Whether it is the actual desert heat causing an image distortion, or if it is a combination of a wide lens with the desert heat, the actual wavy distortion of the image is something I have never seen before. It's actually kind of cool.

Did anybody else notice this?
Does anybody have an explanation for this?