The human ecology of climate change - Climate Change: Biological and Human Aspects - page 388

Finally, the IPCC (IPCC, 1990) estimated that the total emissions of carbon from
fossil fuels between 1850 and 1987 were around 200 GtC ( ± 10%). This is nearly

double the IPCC's estimate of 115 GtC ( 10%) for carbon release due to historical

changes in land use (deforestation, etc.). This, and that two-thirds of fossil fuel
emissions over this 120-year period took place in its last three decades, explains the
importance of recent fossil fuel carbon releases to climate change and why climate
forcing has dominated matters only towards the end of the 20th century. With the
prospect of ever larger fossil fuel releases in the 21st century (as demonstrated by
each subsequent IPCC assessment since 1990), the implication is that the thrust of
21st-century policies to control atmospheric concentrations of carbon dioxide need
to focus on the energy dimension (see Chapter 8). It also explains why the political
manifestation of climate concerns became more marked at the 20th century's end,
with more severe impacts anticipated in the 21st century, even though Svante August
Arrhenius identified the problem as far back as 1896.

±

7.2.2 Futureenergysupply

Nobody can predict the future. However, we do know with certainty the historic
pattern of energy production and the present situation. We also know, as described
earlier in this chapter, the likely future population and economic trends. Overall this
suggests that, barring major disruption of global society, demand for energy will
increase. How will the increased demand for energy be met and what will this mean
in terms of carbon dioxide emissions?
The IPCC's 2007 report (IPCC, 2007a) and their forecasts for 21st-century global
warming are based on a series of future scenarios developed in 2000: the Emission
Scenarios - IPCC Special Report (IPCC, 2000). These scenarios vary from their
lowest (which forecasts marginal growth in emissions to the middle of the century
followed by a decline to just below 1990 levels) to their highest (which predicts an
increase in emissions up to five times 1990 levels by the end of the century). Again
remember, carbon dioxide accounts for more than half of anthropogenic warming
(see Figure 1.2).
The pattern that the IPCC emission scenarios outline for methane, the next major
greenhouse gas contributing to anthropogenic warming (about 18% in 2005; Figure
1.2b), proportionally follows that of their carbon dioxide scenarios. This is because
methane too is either population-driven (needing an increased area of rice paddies
and number of enteric fermenting animals) and/or energy-related (needing more gas
drilling and venting). However, in the future this may not be so, as the technical and
energy options can vary.
Whatever the future, the IPCC predict a range of possible futures and it is this that
drives their core warming forecasts (see Table 5.1). So, what are the energy possib-
ilities and options? Excluding environmental costs, the cheaper options (excluding
long-term environmental and social costs) include the Business-as-Usual (B-a-U)
scenario; that is to say, humans broadly continue the present pattern of energy-
resource consumption. The reason for this is that no extra cost is required to develop
and implement new energy technologies. In this scenario we would continue to rely
heavily on fossil fuels as long as reserves will allow throughout the 21st century. The