It appears Al Gore got things completely wrong. I mean, totally wrong, 180 degrees wrong. Back-asswards, as they say.
I watched 'An Inconvenient Truth' a couple of times. One thing always bothered me and that was that in the historical record, the temperature peaks always came before the CO2 peaks. Yet if CO2 was the cause of the temperature rise, then the opposite should be expected: the temperature peaks should have occurred at or after the CO2 peaks. That was not the case. Why? That question was never answered.
Now I have the answer. It wasn't CO2 that caused the temperature rises at all. The oceans heat up first, perhaps due to volcanic activity. That causes the 'dead zones' to grow and plume hydrogen sulfide, which strips away the ozone layer. The warming oceans then release the methane contained in the methane clathrates into the atmosphere. The temperature peaks occur when the methane peaks in the atmosphere; methane is a much more powerful greenhouse gas than CO2. Over time the methane degrades into CO2, so the atmospheric composition changes from methane to CO2, a strong greenhouse gas to a weaker one. As that occurs the temperature begins to come down even as the CO2 levels continue to rise and eventually peak. Also, the hydrogen sulfide and methane cause much or all of the Earth's surface to burn, both being highly flammable gases, and that too adds to the atmospheric CO2.
Is CO2 a greenhouse gas? Yes, it is. But it has not been CO2 that has been the warming culprit in Earth's history; it has been methane and hydrogen sulfide, mostly methane insofar as the heating of the planet is concerned. The CO2 comes after the burning and the methane releases. Thus, CO2 is not so much the cause as it is the effect. This fits the data much better than Al Gore's simplistic CO2-did-it-all theory, and this explanation answers that heretofore unanswered question: why did the temperatures peak before the CO2 levels peaked?