Actually, when it's winter in the northern hemisphere, the earth is closer to the sun than it is in the summer. It's just that because of the tilt of the earth, the sun's rays hit more directly in the northern hemisphere during the summer. Southern hemisphere seems to have more extreme temperatures -- when the earth is closer to the sun, they're getting the direct summer rays, and vice versa.
Of course, most of what I know about southern hemisphere temperatures is from reading The Thorn Birds years ago! ;-)
I still say that the Sun did it.