by Odin » Fri 03 Mar 2006, 00:36:35
$this->bbcode_second_pass_quote('bobcousins', 'I')t's an interesting theory. It is really tough to isolate the dozens of different forcings that affect climate.
Ruddiman's theory is that humans have been influencing climate ever since we developed agriculture, over 8,000 years ago. A major die-off would presumably coincidence with reduction in fossil fuel burning, so there would be a large reduction in CO2.
Unfortunately, the climate scientists can only make definite statements about the immediate future, further than that they don't really have much of a clue. We know at one extreme there is snowball Earth, at the other runaway global warming. Somewhere in the middle, there are one or more switches that flip the direction, but we don't have much idea where they are. We don't know what triggers glaciation for example. My theory is that reduced CO2 causes it, others say excess CO2!
I don't think IPCC even model PO at all - one study said the IPCC "Business As Usual" is impossible as it assumes that CO2 continues rising linearly to 2200, and takes no account of oil reserves.
There is discussion whether we are at the end of the interglacial period - or whether this is a long one and we are half way through. If we reduce CO2 below pre-industrial levels, that could put us back into the regular interglacial happy zone - or be the trigger of the next glacial advance. We just don't know.
The problem with Ruddman's hypothesis is that there was a long interglacial 400,000 years ago, The unusual length of the current interglacial, just like the one 400,000 years ago, may just be a result of mismatched Milankovich cycles; the precession cycle is in the right configuration for a glaciation to start, but the tilt and orbital eccentricity is not.
"Peak oil is not an energy crisis. It is a liquid fuel crisis." -Starvid
The 2nd Law of Thermodynamics only applies in a closed system; Earth is NOT a closed system.