It's the geology stupid
A few other trifflingl little events did happen in the Miocene.
Antarctica separated, Africa and Europe met up, the Indian ocean stopped flowing into the Med the Andes and Rockies formed. http://www.ucmp.berkeley.edu/tertiary/mio/miotect.html
On the other hand it was before the iPhone - so evidence that iOS causes global cooling and so long as we stay away from Android and buy American we are safe.