Margin of Error

I've started investigating the predictions made by GW believers, and in particular how the predictions have changed over the years. It turns out that the predictions, as I expected, are all over the map: the climate will get hotter in the next 100 years, but who knows by how much, and who can say what'll happen? This isn't of course how it's pitched. But it's what the numbers are telling us. Allow me to explain.

The IPCC (Intergovernmental Panel on Climate Change) predicted a rise of mean global temp by 9 to 12 degrees Celsius in 1990, then .8 to 3.5 degrees Celsius in 1996, then 1.4 to 5.8 Celsius in 2001. There are a couple of points here. One, the absolute differences between the three predictions are huge, a fact that ought to worry anyone who's invested much of their intellectual energies into believing that we know what we're saying. Two, the relative differences (the low to high predictions for each year) are huge, as well. In the 2001 predictions, converting to Fahrenheit gives us a range of 2 to 10 degrees. What the heck? This effectively says nothing; even simpleton GW skeptics like me can see that an eight degree range allows for vastly different weather scenarios.

We might forgive the blatant variations in these predictions by noting that they all point to some warming trend (although, after my unscientific survey of this debate, I'm inclined to believe that the climate will be cooling, not warming, in the next 100 years-- but who knows?). True. But I wouldn't plan your picnic around these numbers, because if you look at them, they tell a clear story: who knows?

Source: http://weathersavvy.com/Q-Climate_Global_PredictionsAccurate.html