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I have a 4 simple questions that I think have big implications. Even though they have yet to be answered with any great certainty we should demand the answers before jumping to conclusions. 1. Since the Earth has been much warmer in the geologic past than it is now, shouldn't we determine "definitively" what caused those warmer climates before we claim that the present warming trend is a result of only anthropogenic intervention? 2. In other words could those same variables that created a warmer climates in the geologic past (prior to human existence) be responsible for the present warming trend? 3. If not, can it be proven that those ancient variables are not responsible/contributing to the current warming trend? 4. Have climatologists accounted for all possible variables for their current models, and if so how do they now they have? It seems to me there are a to many unanswered questions to blame humans for the current warming. I have no vested interest I only have a master of geological sciences degree and these questions have not be answered to any degree of certainty. By the way in the big realm of things considering the age of the Earth, 4.5 billion years, we have only had ice caps for a mere ~6 percent of that time. In otherwords its not normal in that perspective for the earth to have polar ice caps. So again how do we know that there are not other unaccountable variables at work causing the current warming trend along with possible human enhancement of the process?