I can give it a stab but the answer relies on science so you may not like it.AK-47 said:Groggy, how can you say that when anthropogenic climate change hinges on global temperatures and natural variability of the global coupled climate models?? The TAR keeps showing multi-model results for future changes in climate, but since TAR is an unprecedented internationally coordinated climate change experiment thats been performed by over 23 models from around the world, how can you get a variable output of surface temperatures versus atmospheric temperatures??
Can you please answer that question for us??
Models are different from each other mainly because of the 'environmental sensitivity' put into the model. This means that scientists project the impact of the increasing heat stored on earth differently. What this means is that different models predict the effects of climate change differently. For example we all know that excess heat will cause a diminishing of the arctic ice cap and the ice cap will create a feedback loop because of the changes in albedo comparing the ice to water. Where the models differ is that a small difference in the size of the ice cap will create diverging predictions.
The same issues apply to the effects of forest fires, changes to ocean and air currents, the amount of heat stored in the oceans, volcanic activity, and pretty much any other factor involved. Scientists creating the model set the sensitivity for each factor as their experience best sees them but as differences less than 1% in the actual sensitivity can cause a wide range of predictions.
Of course we are talking about science so environmental scientists are constantly comparing predicted values to actual and refining their models as they learn more. As MF said, science is based on evidence and as more evidence is gathered, the models are adjusted. If the models were as far off as MF states, they would have been thrown out and not refined.