Sustainability and policy - Climate Change: Biological and Human Aspects - page 460

8.2 Globalenergysustainabilityandcarbon
An overview of the history of human energy-resource production and consumption is
given in section 7.2. Figure 7.9 shows how the growth in global energy consumption
roughly quintupled in the latter half of the 20th century and that this energy provision
was by far dominated by fossil fuel consumption. For this reason alone, it is easy to
see how any greenhouse impact from the addition of carbon dioxide became more
marked at the century's end. It also suggests - should such trends continue - that
climate change impacts will continue to increase. However, in terms of possible
resource consumption and availability (as opposed to biological impact), how likely
is it that we could continue trends in a B-a-U way?
The IPCC have in part answered this with their B-a-U scenarios, but these only
cover the 21st century. As we have seen, in geological and biological terms a century
is insignificant. So, what are the prospects for continued profligate fossil carbon
consumption given the likely exploitable geological base?
The Kyoto Protocol calls for a reduced overall level of carbon emissions but,
to make the math easier, and allowing for just some increase in consumption by
developing nations, let us assume that carbon emissions stabilise in the near future.
How long can we continue to consume fossil carbon at near-current rates? From
Chapter 7 we can see that we have over two centuries of coal, and while oil and gas
will run out long before then (at present rates of consumption), future economically
recoverable fossil reserves (i.e. reserves not currently economically recoverable)
could extend the potential fossil fuel era at current levels by another century or so, to
over 300 years. Indeed, there are a number of resources, such as low-grade coal and
orimulsion (a high-sulphur water/oil mix), that could be harnessed if the price were
high enough to cover the extra processing costs.
Currently (using data from 2011) we are releasing over 8 Gt year − 1 of fossil carbon
into the atmosphere, of which around 4 Gt of carbon (GtC) accumulates. Of course
there is also the deforestation factor to take into account. Deforestation, though, will
not last at the current rate for 200 years as the forests will have gone by then, so this
dimension of land use may not be a carbon source in the long term. Then again, there
are other carbon sources and the possible atmospheric accumulation from soils as the
boreal climate warms (and that of other areas with high soil carbon). There is also
the confounding factor of reduced ocean absorption once the oceans have absorbed
a critical amount of carbon dioxide. So, making long-term estimates is a complex
business.
Nonetheless, a-back-of-an-envelope calculation (which, if good enough for Arrhe-
nius is good enough for us) suggests that if total fossil fuel consumption continues
as it is now (1995-2005) for up to two (or more) centuries, to use up our currently
commercially available reserves (and without using some form of carbon-capture
technology), then we will easily increase the atmospheric concentration of carbon
dioxide to over three or four times pre-industrial levels, as opposed to around 33%
above pre-industrial levels, which is where we are today, early in the 21st century. This
carbon emission, if continued for two or more centuries at current levels (through