Pretty sure global warming is referencing the global affects, not regional ones. You can't make a global argument based on local temperature increases just like you can't make an argument that global warming is causing cooler summers based on the numerous regions that have experienced cooling in the same reference period. Also these are average temperatures increases, not summer high temperature increases.

It really doesn't - my source shows average summer temperatures (Th - Tl / 2). This does not say that those regions are experiencing high temperatures that are that much warmer, but that on average (including overnight lows) they are warmer.