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Politics : The Environmentalist Thread -- Ignore unavailable to you. Want to Upgrade?

To: TimF who wrote (19402)	1/7/2008 1:45:20 PM
From: neolib	Read Replies (2) \| Respond to of 36921

If I were comparing AGW & evolution I would equate the evolutionary claim of common descent from a single (or very few) original life form(s) to the AGW claim that current global temps are being forced up primarily by human actions. I think that is a much better comparison than what you listed. The evidence for each is similar, and there are also similar gaps. In the case of AGW, we have identified the fundamental mechanism (Greenhouse gases and radiation balance), but the questions remain that perhaps some stirring around of heat issues within the planet might somehow mitigate things and prevent a temp rise. Please note that the overall science behind the radiation balance, is quite straight forward. The equivalent issue in evolution is that we know about DNA and we know that it is modified and the modifications are passed on. The problem in evolution is that there are significant difficulties in the specifics. For example, there is no nice explanation for the "sudden" appearance of larger life forms and the radiation of complexity from the Cambrian period. With AGW, there is zero doubt that increased CO2 causes higher temps (other things held constant) but there is room for speculation that when the other things change as a result, something might magically flip things in the reverse direction. An example which many bashers cling to is cloud cover. If more GHG's either directly through warming, or by some other means (chemistry?) induced more cloud cover, than the cloud effect might more than mitigate the CO2 temp rise. Or increased equitorial temps might drive more heat transport out through the poles. Things like that. The thing to note is that these explanations claim that increasing temps result in some process which then drives a decreasing temp, even though the original process which increased temps is still in place. It could happen. On a 2D graph, imagine you have a series of peaks and valleys. As you go left to right you are climbing up to a peak. Lets call that process GHG heating. Now if GHG's were removed, the process would reverse direction and the temps would fall (sliding back down the graph from right to left). Instead, it is possible that without reducing GHG (or by adding more) you continue to the right, reach a temp peak, and then slide down a slope (left to right) which is a decrease caused by some negative feedback which overwhelms the rising GHG. It is such things which are the uncertainty in AGW. However, all of these processes are much simpler to understand and model than are evolutionary gaps. As new data comes in, ocean, atmospheric, and land models are improved, and with better computers, finer grids are used, and the accuracy keeps going up. With evolution, we can do something similar which is to statistically examine current genomes to tease apart the evolutionary history. So in AGW, as each contribution to global temps gets accounted for better and better, we can assign fractional attributions of climate change to them. You can find such graphs such as this one: en.wikipedia.org Similarly, both from cladistics based on morphology, and now from genomics, we can also state that all life seems to have come from a common ancestor. But this is largely the result of what we should call a very large and complex model. It is not proof in some sense, and certain people will never accept it as proof.