Global warming is an unknown. If one were to look at the Vostok core patterns you can see that we are higher than other peaks and are perhaps sustaining it longer, it doesn't extrapolate into a direct corelation of human = global warming. The earth, as with all living ecosystems, operates on a cyclical pattern.
We may have disrupted that pattern a little bit, but we don't have the information to say we have irreversably changed that pattern just because our interactions with the environment. Furthermore, a huge portion of the increase and sustained plateau started occuring *THOUSANDS* of years ago, far before the industrial revolution started polluting on a global scale. Consider the fact that we are measuring tempertures of perhaps 300 years to the events of 50 years on a scale of increase of more than 2000 years and then coming to the definitive conclusion that it is our actions of less than 2.5% of the 2000 years that has cause temperatures to go higher.
http://en.wikipedia.org/wiki/Image:Vostok-ice-core-petit.png
To suggest otherwise is akin to using the temperature and thermostat in your house to extrapolalate it's affects on tempertures within a mile of the house.
I am not saying we shouldn't reduce our emissions. I hate SUV's, I think everybody should start driving 30mpg cars, to start. I also think we need to come up with better mass-energy production (expansion of fission, wind, solar, tidal, more investment in fusion).
However, to run around like chicken little's because less than 50 years of temperature increases on a scale of massive 2-3 thousand year peaks and then concluding it's us causing those peaks, it just stupid.