It's not Global Warming...it should never have been called that in the first place. It's CLIMATE CHANGE. If you believe National Geographic Magazine is a reliable source of information, look at this: http://news.nationalgeographic.com/news/2004/12/1206_041206_global_warming.html
Or, you can read articles on the subject published by NOAA, NASA, and more recently, BEST (which was partially funded by the Kock Brothers because the primary of the research study was one of the greatest skeptics...if you don't know who they are, just Google it).
Of course, some people are not going to believe the Science until they have sea water in their beach front home's living room.
There are natural cycles of climate change, but the RATE of change has increased with increased human activity on the planet, so draw whatever conclusions you choose from the overwhelming evidence that the chit is going to hit the fan in a big way within the next 100 years or so.