Dunno if you subscribe to the theory, but global warming explains a number of things happening worldwide, including the above-average temperatures in many of the major cities worldwide.
Abnormal droughts, floods, weather events, the rising sea level, glacial retreat, even seemingly random things like the disappearance of honey bees (Colony Collapse Disorder) and the appearance of mosquitoes in new areas are often attributed, at least in part, to global warming.
Wiki isn't the end-all of references, but it's an easy start and informative read and will give you ideas on where to go next -- http://en.wikipedia.org/wiki/Global_warming.
With the increased fuel costs added onto the record high temperatures, some people are worried about an especially rough summer. We might even see some riots if the rising energy costs force rolling brownouts in major cities.