[Note update below. Paul’s updated model is here.]
There’s a lengthy discussion on The Oil Drum of Paul Chefurka’s World Energy and Population: Trends to 2100. I mentioned Paul’s paper in the introduction to the previous post here, and recommend it to anyone interested in an excellent, readable analysis of the relationship between peak energy and global population. It goes a long way toward bringing into focus much of the essence of our global ecological crisis.
I haven’t read all the comments on The Oil Drum, but there’s clearly enough material there to keep an interested reader busy for days. Good stuff.
[10/21/07] Update: See Paul’s newer World Energy to 2050. Given Paul’s reassessment of his WEAP model (see this link, but also Paul’s comments below), a few more words are in order. It seems the key conclusion resulting from over 400 comments on the paper on The Oil Drum was that it did not successfully establish a causal link between energy decline and population decline.
That said, I believe the paper has had real value. First, it does contain excellent examinations of some important issues. Second, getting it in front of large numbers of people who could discuss and critique it has moved the discussion of this hugely important topic. We now have some new indication of how difficult it is to demonstrate beyond doubt a link between energy decline and population decline. It remains, of course, a problem of tremendous importance.
This is all very speculative, of course, but if true, it may in time help clarify the role of peak energy in the looming convergence of major ecological problems. It could turn out to provide a smidgen more hope for the human future. Unfortunately, with a number of key ecological crises underway, some form of population crash remains a clear concern. See the comments for more.
 Converging ecological problems include climate change, mass extinction, deforestation, aquifer depletion, soil erosion, depletion of fish stocks, and more, all in the context of increasing population overshoot and consequent decreasing carrying capacity.