Environmental Engineering Reference
In-Depth Information
probability of exceeding 2 1C temperature increase), with zero budget re-
maining thereafter. However, rather than stabilising, annual fossil-CO
2
emissions are increasing; between 2000 and 2012 the global annual emis-
sions increased by 40%. The challenge, therefore, is significant, both to re-
verse the upward trend in annual emissions and to reduce year-on-year
global emissions by 3-9%, depending on the year at which global emissions
peak and the reductions start (see Anderson and Bows (2011) for an exam-
ination of alternative pathways and emission reduction rates).
35
These
constraints are even more challenging if principles of equity between na-
tions are incorporated. Given that it is developed/OECD nations that are
chiefly responsible for the historical emissions of GHGs that have caused
climate change to date, and which will persist in the atmosphere for decades
to come, a climate regime that does not accord a greater emissions allo-
cation to developing nations is unlikely to be internationally acceptable.
When reasonable allowances for future emissions are allocated to de-
veloping nations, the budget becomes more constrained for developed na-
tions, with timescales for almost complete decarbonisation of their energy
systems necessary well before 2050.
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Having quantified the remaining global carbon budget associated with 2 1C,
we can now consider the availability of shale gas within this limit. Table 4
shows the existing reserves and resources of fossil fuels in the world and the
amount of CO
2
that would be emitted if they were burnt without abatement
measures. Burning conventional reserves of oil and gas alone would likely use
up the entire CO
2
budget, before burning any coal at all, or eating into the
resources that are at present uneconomic to extract. Shale gas reserves repre-
sent between 1.8 and 6.5 times the global budget and, if resources are included
as well, there is sucient shale gas to occupy the budget 5.6 to 17.7-times over.
Table 4 Global energy reserves and resources and the associated CO
2
emitted if
burnt unabated.
Total
Potential
CO
2
(Gt)
Reserves
(Gt CO
2
)
Resources
(Gt CO
2
)
Reserves (EJ)
Resources (EJ)
Conventional oil
4900-7610
4170-6150
349-574
297-465
665-1009
Unconventional
oil
3750-5600
11 280-14 800
254-444
765-1172
1102-1496
Conventional gas 5000-7100
7200-8900
271-414
391-519
684-898
Unconventional
gas
20 100-67 100 40 200-121 900
1091-3912 2182-7107
3383-10603
Coal 17 300-21 000 291 000-435 000 1510-2125 25 395-44 022 30 296-44 810
Source: Global Energy Assessment Table 7.1.
51
Note that resource data are not cumulative and
do NOT include reserves, the GEA also includes additional occurrences which are not included
in the figures above; these include 440 000 EJ unconventional oil and 41 000 000 EJ
unconventional gas. Conversions from EJ to CO
2
use IPCC emission factors for crude oil to
estimate conventional oil CO
2
, shale oil figures to estimate unconventional oil; natural gas
emission factors for both conventional gas and unconventional gas and the emission factors for
coking coal for coal. The upper and lower emission factors for each fuel have been applied to the
upper and lower CO
2
estimates, respectively.
