Guerrilla knitting?!

I have heard of this phenomena, and even met the culprits, but never seen the evidence in the flesh. And there I was looking out of the window at the traffic lots and thought....eh?

I am certain the tree is thankful for it, -2 C and getting cooler overnight, just what you need a knitted scarf...jumper...what would you call it, a "trunk-per", perhaps?