1. about... hm 6 billion years + a couple of hundred millonSince the topic is now open, let me ask another theoretical question. For those of you who think it's a serious issue, I want to know three things. First, how long do you think the earth has been in existence. Second, do you believe in the scientific method. Third, what data do you base your opinion on?
I believe global warming is a propaganda tool. I also believe the earth is self-balancing, self-sustaining. That does not mean that I think the earth deserves no respect at all since we do all live on it. All I think is that we have very limited data, and while the current data does show a trend, it's not nearly enough to convince me that the way we do everything has to change or we'll all be toast. Come back to me after you've collected data over a period of a few thousand years.
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You can only go so far with that.