There are a lot of problems with the scenarios being described, and they are obvious ones that I have to think people are simply failing to see.
For one - demand destruction. Most of the world has 'self adjusting' market economies now, the concept does work. No, these won't create energy from nothing. What they will do is cause prices to go up as energy becomes more scarce. Look at the very charts you reference, in the period 1979-1983 there is a huge drop in oil consumption while natural gas levelled out. The world population was not affected.
A most important fallacy here is the direct causal relationship between energy and world population. Consider this : half the world lives on $2 per day or less. Over 1.2 billion people live on $1 per day or less.
http://www.unfpa.org/swp/2001/english/ch03.html
"More than a billion people cannot fulfil their basic needs for food, water, sanitation, health care, housing and education. Nearly 60 per cent of the 4.4 billion people living in developing countries lack basic sanitation, almost one third do not have access to clean water supplies, one quarter lack adequate housing, 20 per cent do not have access to modern health services, and 20 per cent of children do not attend school through grade five. Worldwide, 1.1 billion people are malnourished, unable to meet minimum standards for dietary energy; and protein and micronutrient deficiencies are widespread.8 Nearly 2 billion people in developing countries are anaemic."
The point is that you don't really need much energy to live. In fact, roughly two-thirds of world population already lives and multiplies without the comforts of western civilization.
Couple this with the market economy, and the picture becomes clear. *IF* the peak energy / peak oil theories are correct, we will have a very very long period of price increases accompanied by greater and greater levels of conservation and consumption declines.
In fact, the initial stages will probably be larger consumption declines than than drops in supply. Consumption can drop a *lot* faster than supply drops.
*None* of these human and market factors are ever throw into the analysis by these doomsayers. The most I ever see from them is a sideways remark about how the decline will run over human ingenuity, conservation, and market forces acting on each other to adjust. So far, these doomsayers have been wrong, and I expect they will continue to be wrong for quite a while longer.