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improvements in the efficiency of buildings, conservation, electrification of the vehi-
cle fleet,^10 and a decline in population growth. However, it is hard to envision any of
these factors dramatically altering the message of Fig. 4.4. Thus, the choice is clear:
either the world charts a course towards supplying about half of total, global energy
by renewables around year 2060, or CO 2 emissions will exceed those of RCP 4.5.
The majority of the climate modeling community believes that for the 2 °C
global warming upper limit of the Paris Climate Agreement to be achieved, CO 2
emissions must be reduced to match those of RCP 2.6 (van Vuuren et al. 2011 ). As
detailed in Chap. 2 , forecasts of global warming conducted using our Empirical
Model of Global Climate suggest the Paris target will likely be met under RCP 4.5.
Regardless, we now extend our forecast to RCP 2.6.
Figure 4.5 illustrates the transformations that will have to occur to match the RCP
2.6 emissions of CO 2 (van Vuuren et al. 2011 ). The design of RCP 2.6 employed car-
(^10) Due to the inherent inefficiency of internal combustion on the small scale of a car engine, electric
vehicles release considerably less CO 2 per mile traveled than traditional vehicles, even if the elec-
tricity used to charge the vehicle’s batteries is generated by combustion of fossil fuels.
Coal
Natural Gas
Liquid Fuels *
RCP 8.5
RCP 4.5
RCP 2.6
- No CCS
b
1990 2000 2010 2020 2030 2040 2050 2060
10
20
30
40
50
60
70
World Energy Consumption and CO 2 Emissions, Modified to Meet RCP 2.6 in 2030
History
Nuclear
Renewables
Coal Fossil Fuels CCS
Natural Gas
Liquid Fuels * - No CCS
a
5.7%
49.2%
38.4%
(^100) 6.8%
200
300
400
500
600
700
800
900
1000
Energy Consumption (quad BTU)
Gt CO
yr 2
-1
Fig. 4.5 World energy consumption and CO 2 emissions, modified to meet RCP 2.6. Same as Fig.
4.3, except the sum of CO 2 emissions from coal, natural gas, and liquid fossil fuels has been modified
to match RCP 2.6 (van Vuuren et al. 2011 ) starting in year 2030. The time series of consumption of
energy produced by renewables has been held fixed at the same value used for the RCP 4.5 projection
(Fig. 4.3). The remaining gap has been allocated to carbon capture and sequestration (CCS), a policy
option considered by the authors of RCP 2.6. See Methods for further information
4 Implementation