China’s catching up alone would roughly double world consumption rates. Oil consumption would increase by 106 percent, for instance, and world metal consumption by 94 percent. If India as well as China were to catch up, world consumption rates would triple. If the whole developing world were suddenly to catch up, world rates would increase elevenfold. It would be as if the world population ballooned to 72 billion people (retaining present consumption rates).Yes, this is the problem. We can't equitably sustain the impact we already have. Which means that there are only two possible ways out of an absolute decline:
Some optimists claim that we could support a world with nine billion people. But I haven’t met anyone crazy enough to claim that we could support 72 billion. Yet we often promise developing countries that if they will only adopt good policies — for example, institute honest government and a free-market economy — they, too, will be able to enjoy a first-world lifestyle. This promise is impossible, a cruel hoax: we are having difficulty supporting a first-world lifestyle even now for only one billion people.
1) Abandoning the pretense that we have any interest in being fair
2) Reducing the impact per unit of wealth elevenfold
And that is just to break even!
Consider what an economist would consider business as usual.
Consider 2.5% annual growth, wherein the rest of the world can eventually catch up entirely to our final level. Let's give it fifty years of more growth. Then we hold still and wait for the rest of the world to catch up to us; this will provide a lower bound. (Things are worse if we keep growing after that, but this is a good place to start.)
Plus we suppose a 40% increase in population that the demographers are telling us is what to expect.
And now consider what the world what have to do to break even on impacts.
OK, the 2.5 % growth for 50 years amounts to a 3.4 fold increase in wealth for us. If the population does not increase, that means the 11-fold increase in the prior calculation (for others to catch up only to 2008 levels in the west) has to be multiplied by 3.4 to catch up to the west, plus another factor of 1.4 to account for the increased population.
As a consequence, the impact per unit of wealth has to decline by a factor of 11 * 3.4 * 1.4 = 52.9 .
In order to support business as usual without increasing net impact or abandoning any claim to international equity, impact per unit wealth has to decrease by more than a factor of fifty. Even that may not be sustainable: that is what is needed to fulfill the implicit promise of a growth economy to the rest of the world for another fifty years without increasing the RATE at which the earth is damaged. And even so, the growth idea implies continuing reduction in impact per unit of wealth thereafter.
This entirely leaves aside arguments from energy availability. It's completely sink-driven. For the most part, supply-side energy depletion arguments (peak all) are "served concurrently". They don't make matters easier, but at least they don't add new multipliers.
What really has me dismayed is the scenario that the west will indeed abandon the pretense of international equity and try to become explicitly cynical and apartheid. This would leave the numbers much more plausible, but the world in sorry shape, mutually hostile, sectarian and violent by choice.
The recent rise of China in particular, and to a significant but lesser extent of India, will probably preclude success of this strategy. I hope so. In that scenario, the "growth" would all be channeled to the military in any case, essentially leaving individuals no additional wealth.
As Diamond points out, our existing patterns, especially in North America, are very wasteful; little actual well-being results from much of the high-impact activity. Oddly, in this wastefulness there is some hope, hope that our inevitable "decline" will not be too severe or disruptive, hope that what we can trim is mostly useless anyway.
Maybe there is some way to impose some sort of "growth" on this just to humor the economists, the bankers and the pension funds, but in actual fact our North American rate of impact on the world is so unsustainable that we will either see a long period of decline or something vastly worse.