Geology Reference
In-Depth Information
Fig. 10.1
Results of the carbon cycle model used (Valero
et al., 2011)
sonably good estimate of future atmospheric CO 2 requires the use of a carbon
cycle model that simulates the carbon uptake of the oceans and the terrestrial bio-
sphere. Additionally, it requires knowledge of the fossil fuel resources stock as well
as a projection of future emissions from fossil fuel combustion and land use change
(emissions scenarios).
The carbon cycle comprises a variety of processes which develop in timescales
ranging from hours to millions of years. The shortest processes are photosynthesis,
respiration and the interaction of the atmosphere with ocean surfaces and soil. The
long-term processes consist of the carbon exchange between rocks and the superficial
system (ocean, atmosphere, biosphere and soils) (Berner, 2003). The carbon cycle
model adopted in Valero et al. (2011) is Tomizuka's box (Tomizuka, 2009), which
despite its simplicity, offers an effective representation of the carbon cycle and a
reliable projection of its future behaviour.
Results of the model using historical CO 2 emissions data (Houghton, 2009; Mar-
land et al., 2008) are shown in Fig. 10.1. Historical atmospheric CO 2 data used in
this figure is taken from Neftel et al. (1994) and Tans (2009).
Once the carbon cycle model has been selected, the next step is to determine the
total amount of carbon stored in fossil fuels. This is carried out using information
regarding the conventional and non-conventional world fossil fuel reserves provided
in Chap. 6 (see Table 6.7), together with the carbon emission factors (CEF, which
are given in mass of carbon per energy unit of fuel) provided by the IPCC (Eggleston
et al., 2006). The results are summarised in Table 10.1.
From Table 10.1 one can see that the total carbon stored in conventional fossil
fuel reserves is about 2,000 GtC, a figure much smaller than the commonly used
value of 5,000 Gt (Bala et al., 2005; Lee and Holder, 2001; Lincoln, 2005). This is a
significant result since any emissions forecast relies heavily on such information. It
 
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