Energy and Human Ambitions on a Finite Planet, 2021a

30
3 Population
Underlying virtually every concern relating to our experience on this
planet is the story of human population. The discussion of continued
energy growth in Chapter 1 was based on the historical growth rate of
energy, which is partly due to growing population <strong>and</strong> partly due to
increased use per capita. But the notion that population will continue an
exponential climb, as is implicit in the Chapter 1 scenario, is impractical—
one of many factors that will render the “predictions” of Chapter 1
invalid <strong>and</strong> prohibit “growth forever.”
So let’s add a dose of reality <strong>and</strong> examine a more practical scenario.
Americans’ per-capita use of energy is roughly five times the global
average rate. If global population eventually doubles, <strong>and</strong> the average
global citizen advances to use energy at the rate Americans currently
do, 1 then the total scale of energy use would go up by a factor of 10,
which would take 100 years at our mathematically convenient 2.3%
annual rate (see Eq. 1.5; p. 5). This puts a more realistic—<strong>and</strong> proximate—
timescale on the end of energy growth than the fantastical extrapolations
of Chapter 1.
Although the focus of this chapter will be on the alarming rate of
population growth, we should keep the energy <strong>and</strong> resource context in
mind in light of the overall theme of this book. To this end, Figure 3.1
shows the degree to which energy dem<strong>and</strong> has outpaced population
growth, when scaled vertically to overlap in the nineteenth century.
From 1900 to 1950, per-capita energy consumption increased modestly,
but then ballooned dramatically after 1950, so that today we have the
equivalent of 25 billion people on the planet operating at nineteenth
century energy levels.
Since population plays a giant role in our future trajectory, we need to
better underst<strong>and</strong> its past. We can also gain some sense for theoretical
3.1 Population History ...... 31
3.2 Logistic Model ......... 33
Overshoot ............ 35
Logistic Projection ....... 38
3.3 Demographic Transition ... 38
Geographic Considerations . 41
Transition Cost ......... 44
3.4 Touchy Aspects ......... 46
It’s Personal ........... 46
Population Policy ....... 47
3.5 Upshot: It Depends on Us .. 48
3.6 Problems ............. 48
1: . . . so that global average energy use per
capita increases by a factor of five from
where it is today
Global Power (TW)
18
16
14
12
10
8
6
4
2
0
1800 1850 1900 1950 2000
year
25
20
15
10
5
0
Population (Gppl)
Figure 3.1: Population (red) <strong>and</strong> energy dem<strong>and</strong>
(blue) on the same plot, showing how
much faster energy dem<strong>and</strong> (power) has
risen compared to population, which translates
to increasing per-capita usage. The
vertical axes are scaled so that the curves
overlap in the nineteenth century. [14–16].
Photo Credit: Tom Murphy
© 2021 T. W. Murphy, Jr.; Creative Commons Attribution-NonCommercial 4.0 International Lic.;
Freely available at: https://escholarship.org/uc/energy_ambitions.