The Romans grew wine grapes on the British Isles.
During the Middle Ages, the Netherlands had a Mediterranean climate.
That was 500 years ago, and we've since seen times of harsh winters and colder climates, whereas it seems we're now slowly moving back towards what things were like in the Middle Ages. When people burnt lots and lots of wood, with the CO2 and all. (To stay on the topic of wine - there are now certain grapes that can grow into successful crops here.)
Moreover, scientists agree that the earth seems to warm up quite significantly right before an Ice Age. I wouldn't be surprised if that's what is in fact happening.
You can believe the theory you were taught, Scotsworth. I believe in the theory that mankind only account for a very small percentage (something like 2% if I remember correctly) of the total amount of global warming. That there might be an ice age coming, or that perhaps the increased heat has to do with the cycle of activity of the sun. There are multiple theories, and we can only guess.
In addition, I've always thought this quite curious:
The oceans absorb CO2.
Global warming melts ice.
North and South Pole ice turns into sea water.
Therefore, there is more ocean to absorb CO2, right? Right?!
Does this mean I won't try to reduce my carbon footprint? No.
But. I must say I find it strange that we are being hassled to use certain light bulbs here in the Netherlands, when the US can't even be bothered to stop driving those ridiculously humongous cars, or put any other measures in place.