The human ecology of climate change - Climate Change: Biological and Human Aspects - page 372

extreme example, a tyrant bent on domination through aggression. This population
will divert resources to those ends rather than improving environmental efficiency.
Such acts lower the carrying capacity of the environment. The inescapable conclusion
in greenhouse terms is that it is the choices we make as a global society that determ-
ine our ability to handle climate change concerns, and that there is not some fixed
global level of fossil fuel consumption that can be considered ideal. This may seem
counterintuitive but can be illustrated by considering a power station that burns fossil
fuels whereby all the carbon dioxide generated is isolated through carbon capture (see
Chapter 8). Such a station will not affect the climate through its emissions (though
admittedly it may in other ways) as a normal power station would.
To sum up, although it is extremely difficult to quantify the costs of the global
population's greenhouse impact, the levels of population and affluence do very broadly
relate to the level of impact. However, above and beyond this, it is environmental
efficiency, and specifically the choices made to realise this efficiency, that affects
climate change. This last lies at the heart of much of the next chapter.

7.1.2 Pastandpresentpopulation

The global population of Homo sapiens sapiens (hereafter referred to simply as
H. sapiens ) is currently growing and for many (there are exceptions) this is an
accepted and often unremarked-upon fact of modern life. This is in no small part
because everyone alive today has lived in a world that has seen continuous growth, so
that such growth seems unremarkable: after all, the continuation of the line above and
below one point on an exponential curve looks just like elsewhere on the same line
above and below any other point on that curve. A person today in their late middle age
will have seen the global population grow from a little over 2 billion to more than
7 billion, while a typical undergraduate student aged 19 or 20 will have seen the
population rise some 25% from over 5 billion (see Figure 5.10). Yet our post-Industrial
Revolution period of population growth is not typical.
Joel Cohen (1995) cites the independent estimates of early human population size
for over a million years ago of demographers Edward Deevey Jr and Michael Kremer.
They both estimated the global population at the time to be approximately an eighth
of a million (although Kremer based his estimates on those of Deevey Jr for global
population up to 25 000 years ago). After that time their estimates for population
differed substantially up to the beginning of the Common Era. From

1650 their
figures are joined by similar estimates from five other demographers and together
these present a coherent picture.
If these estimates are to be believed then it would appear that from 1 million to
300 000 years

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the Earth's population of Homo spp. grew slowly from an eighth
of a million to a million. The rate of increase required for this is little over one
person a year. However, 1 million to 300 000 years ago was a period of Pleistocene
Quaternary glacial-interglacial cycles so fairly linear population growth is unlikely
to have occurred. More probable is that the global population was reduced in times of
extreme climate change (such as at the beginning and end of glacials and interstadials)
and grew when the climate was stable. Furthermore, this meta-population of Homo
spp. saw its various component populations (of Homo erectus , Homo sapiens and

bc