Don, Global Warming's somewhat mis-named. The effect of increased greenhouse gasses isn't just an increased overall temperature, it's more extreme weather conditions generally: hotter highs, drier droughts, more and bigger storms, even colder lows on some parts of the planet.
It's true that the earth has a normal warming and cooling cycle that we don't completely understand. For example, 600 million years ago the entire planet was covered by a glacier, even at the equator. Volcanism, with its massive releases of CO2, is the only possible force that could've reversed "snowball earth," but we don't know why volcanism increased when it did, ending snowball earth, nor why it had decreased its activities before that enough to allow the entire earth to freeze over in the first place.
But we've broken those normal heating and cooling cycles. A future ice age would be good news, because it would mean our changes haven't completely destroyed the cycle, but I fear that'll never happen.
CO2's currently the biggest offender, and every car we drive and power plant we fire adds to the problem, but we're getting precariously close to releasing methane and ethane from the world's oceans, currently kept inside the water by massive pressure and low temperature. Methane and ethane are 20 to 100 times worse greenhouse gasses than CO2 itself.
The EPA website has a really good section on Climate Change, if you're interested.