If you want to have an honest discussion on the subject, I would suggest not using the term "global warming". For one thing, it is vague and for anther reason, it just ignites passions that obscure any meaningful discussion.
I would suggest using a term such as 'climate change'. There is no doubt that the earth is in the midst of climate change. It has been since day one and hopefully will be until day...last. last day. end of the planet. You get my drift.
The concern and predictions that science makes regarding climate change is that, as the average temperature of the earth increases, then we will see certain weather trends in regions. Some places are going to get colder, some places are going to get hotter. Most everyone will see increased variation and probably will see increased intensity of weather.
But don't believe me. I do teach a course in climate change, but I suggest reading the data for yourself.
EDIT: Oh, and Ratchet is just poking certain folks. Don't get yer panties in a bunch.