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>Our activities are in no way "natural" any more. Canada and the U.S. in particular saw the harmful effects that man's activities (we both no doubt took liberties that European/Asian countries knew better of) in pollution of the Great Lakes and deaths of smaller lakes because of acid rain. These have largely been addressed such that the Great Lakes are now looking good again and lakes have started to rejuvenate. And my point is that if the relatively small population/activity near the Great Lakes can cause such impacts, why would anyone doubt the deterioration of the planet's natural systems?
>These effects were directly observable/measureable, so there was little argument and lots of willingness to correct the situation.
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Our activities ARE natural, how can the be anything else. We evolved from people who had very little skill into a group that is getting increasingly more complex and as a result, we are able to work on problem solving, etc. We first need to define the problem though, and therein lies the rub. I say there is not enough evidence of global warming being anything more than a normal weather pattern. No one has proven otherwise. In fact, the "facts" that have been offered like melting glaciers have been refuted time after time, when dispassionate investigation takes precedence over social and economic agenda.

>Scientists have the benefit of satellite measurements and complex computer modelling and widespread field measurements now in place. Scientists now have capabilites to analyze ice cores and soil/rock cores to make detailed determinations about the past operation of the planet. Scientists can now communicate very efficiently and across the entire planet. There are nmore scientist alive today than the sum of all the scientists that lived in the past.
>Scientists have always disagreed, and it has happened that scientists ostracized by the community because of a theory have ultimately been proven right and the colleagues wrong.

And so, the global warming theory is now being debunked.

>"Global warming" was close to such a theory. The early promoters were soundly criticized almost universally, but as evidence mounted support grew. Today it is the vast majority of scientists who acknowledge the existence of the problem and most fear that time is short to formidably address the problem before the process becomes irreversible.
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It's all driven by the quest for research dollars. The scientist of the world are going to get research dollars by hook or crook. It's just a matter of which scare tactic lever they wish to turn - Hot or Cold!