Quote:
Originally Posted by Solanum
And one more before, I get on with some work. As you well know the land masses were in a very different position to now during those hot periods you talk about, which resulted in big differences in ocean currents and big differences in climate. That's what I meant about the geology (though I would be surprised if outgassing has remained the same over the last 500 million years - but I have no idea). As I already said, the biology has change a lot since land plants first appeared on earth.
So the bottom line is, how can data on climate 500 million years ago be more relevant than the last one million years?
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Yes, they were, but you have to look at the positions in which they were in the overall context of the climates that occurred when they did. Climates have changed and fluctuated over millions of years but much of the overall basic patterns have remained the same. During the Carboniferous, for example, the climate overall was much the same as now. The climate zones and weather patterns were quite similar, but the CO2 level was 800ppm. That should mean, according to the those that believe it's the CO2 causing the climate change, it should've been much hotter, but it wasn't. What does that tell you??.
Let's look at a time less remote from us than this...the Cretaceous. CO2 concentration was 1700ppm, average global temp was 18 degrees, 6 higher than now. The continents were pretty much recognisable though somewhat out of position, but their distribution relative to one another was similar to today. CO2 levels fell to around 1000ppm by the end of the period and it cooled to around an av' of 16 degrees worldwide. The plant biology of the time was remarkably similar to now. You had conifer forests and flowering plants had actually supplanted most non flowering plants in variety and numbers of species by the mid to late Cretaceous. Apart from the fact you had large munchy biteys running around, the world was remarkably like now, except there was 50% more oxygen around than now. The temperature profile for the Cretaceous is remarkably constant for the much of the period, CO2 levels were not. They dropped 700ppm. What is that telling you about the correlation between CO2 and temperature??. Actually, when the CO2 levels were at their highest during the period, the temps were at their lowest...doesn't quite ring true, does it?? This is despite the fact that warm seas covered much of the continents at the time and carbonate deposition was high.