Research Institute of Innovative
Technology for the EarthScenario analysis of halving global CO2 emissions by 2050
September 20, 2011
RITE, Systems Analysis Group

1. Introduction
RITE has been developing comprehensive scenarios toward sustainable development and climate stabilization
since FY2007 as a part of the “International Research Promotion Program for Global Environment”, which issupported by the Japanese government (The ALPS project, ALternative Pathways toward Sustainable
development and climate stabilization)1)-4). In this paper, the scenario analysis of halving global CO2 emissions
by 2050 by using the DNE21+ model which is a world energy systems model6)7) is outlined. This scenario wasdeveloped based on the medium growth socioeconomic scenario (Scenario A)5) of the ALPS project where thelatest world economic conditions are taken into account.

2. Scenario Analysis of halving global CO2 emissions by 2050
The scenario of halving global CO2 emissions by 2050 relative to 2005 (the halving global CO2 emission
scenario) was analyzed by using the DNE21+ model. The evaluated greenhouse gas is limited to energy-related
CO2 only. Uniform CO2 marginal abatement cost over all the regions is adopted in this analysis, as the criterion
for the minimization of the total world cost.
Scenarios of halving global energy-related CO2 emissions by 2050 relative to 2005 were also analyzed in IEAETP20108) (BLUE Map scenario). In this paper, the analysis in the ALPS is summarized with the comparison
between the ALPS and the IEA ETP2010.
2.1 CO2 emissions and reductions
Figure 1 shows energy-related CO2 emission reductions relative to the Baseline scenario (scenario without
GHG mitigation policy) by technology and sector for the halving global CO2 emission scenario. Figure 2 showsenergy-related CO2 emission reductions relative to the Baseline scenario by technology for the BLUE Map
scenario in IEA ETP2010. The global CO2 emissions in 2050 for the halving global CO2 emission scenario of theALPS are a little smaller than those of the BLUE Map scenario, because CO2 emissions from international
aviation/marine bunkers are treated exogenously in the DNE21+ model.
The baseline global CO2 emissions in 2050 are 57GtCO2/yr and are almost double of the current emissions.
Therefore, three quarters of the baseline global CO2 emissions have to be reduced, meaning that the global CO2emissions have to be one quarter of the baseline emissions for halving the global CO2 emissions by 2050.
The emission reductions are required for various sectors and technologies in order to halve the global CO2emissions. In figure 1, the total emission reductions relative to the Baseline scenario in 2050 are 44GtCO2/yr,
and the shares of emission reductions of electricity generation technologies are 17% by carbon capture & storage(CCS), 14% by renewables, 15% by nuclear and 11% by improvements in efficiency and fuel switching among
fossil fuels, respectively. Large emission reductions in energy end-use sectors (industrial sector, transportation
sector and residential & commercial sector) are also required, and the share of these sectors is almost 40% of
total emission reductions. The emission reduction share of energy end-use sector is almost 50% in the ETP2010.
Although the contribution of energy end-use sectors to emission reductions in the ETP2010 is slightly larger thanthat in the ALPS, the emission reduction share by sector and technology in the ETP2010 is quite similar to theALPS scenario.

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Energy-related CO2 Emissions and Reductions[GtCO2/yr]

60

Electricity generation:
CCS 17%

Baseline Emissions：
57GtCO2/yr

Electricity generation:
Renewables 14%

50

Electricity generation:
Nuclear 15%
40

Electricity generation: Efficiency
improvement & Fuel switchingamong fossil fuels 11%
Other energy conversion
sector 5%

30

Residential & Commercial
sector 12%

20

Transportation
sector 9%

Emissions when halving
global emissions：13GtCO2/yr
10

Industrial sector

17%

CO2 Emission

02010

2015

2020

2025

2030
Year

2035

2040

2045

2050Figure 1 Halving global CO2 emission scenario by sector and technology
Note) CO2 emissions from international aviation/marine bunkers and land use, land use change, and forestry (LULUCF) are not included.

Figure 2 CO2 emission reductions by technology for the BLUE Map scenario (halving global CO2emissions) in the IEA ETP20108)

Figures 3 and 4 show energy-related CO2 emission reductions by region in the ALPS and the IEA ETP2010,respectively. The share of emission reductions of developed countries in global emission reductions in 2050 isalmost 30% in both the scenarios (USA: 13 % and Other OECD: 17% in ALPS, USA: 11% and Other OECD:17% in ETP2010). For developing countries, the emission reductions in China are large and that share in globalemission reductions is 24% and 27% in the ALPS and the ETP2010, respectively. For India, that share is 10% in
the ALPS and 12% in the ETP2010. It is almost impossible to achieve deep global emission reductions such as2

Research Institute of Innovative
Technology for the Earthhalving global CO2 emissions only by developed countries. Emission reductions would require the effective
participations of all major emitters.
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Energy-related CO2 Emissions andReductions [GtCO2/yr]

Baselineemissioins：
Emissioins：
Baseline
57GtCO
2/yr
57GtCO2/yr

Other non-OECD 30%

50
Other OME 6%

40
India 10%Figure 3 CO2 emissions reductions by region for halving global CO2 emissions
scenario

30

China 24%

20

100
2010

Other OECD 17%

Emissions when halving
global emissions：13GtCO2/yr

USA 13%CO2 Emissions

2015

2020

2025

2030
Year

2035

2040

2045

2050

Figure 3 Halving global CO2 emission scenario by region
Note 1) CO2 emissions from international aviation/marine bunkers and land use, land use change, and forestry (LULUCF) are not included.
Note 2) Other OME (Other Major Economies)：Brazil, Russia and South Africa

Figure 4 CO2 emission reductions by region for the BLUE Map scenario (Halving global CO2emissions) in the IEA ETP20108)

2.2 Primary energy supply
Figure 5 shows global primary energy supply in the Baseline scenario and the halving global CO2 emission
scenario in 2030 and 2050. In the Baseline scenario, fossil fuels, especially coal, are main energy source as in thecurrent situation. Costs of wind power and PV which are categorized in “Others” are higher than other energy
sources and their supplies are small in 2050, even though their future cost reductions are assumed.

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In the halving global CO2 emission scenario, coal and oil supply is substantially reduced relative to the Baseline
scenario. On the other hand, nuclear and renewables such as biomass, wind power and PV are induced.
Compared with the IEA ETP2010 analysis as shown in Figure 6, there are no large differences between theALPS and the ETP2010. However, “Others” in the BLUE Map scenario is slightly larger than that in the halving
global CO2 emission scenario (The difference is mainly caused by the difference in wind power. See the nextsection.).
24000

OthersPrimary Energy Supply [Mtoe/yr]

22000
20000

Biomass &Waste

18000
16000
14000

Hydro &Geothermal

12000

Nuclear

10000
Natural Gas

8000
6000

Oil

4000
2000

Coal

0Baseline

Halving global
CO2 emissions

Baseline

2030

Halving global
CO2 emissions
2050

Figure 5 Global primary energy supply in the Baseline scenario and the halving global CO2 emission
scenario

Figure 6 Global primary energy supply in the Baseline and the BLUE Map scenario in the IEAETP20108)

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Research Institute of Innovative
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2.3 Electricity generation
Figure 7 shows global electricity generation in the Baseline scenario and the halving global CO2 emission
scenario with IEA ETP2010 analysis. In the Baseline scenario, coal power generation is widely used as a cost
efficient technology until 2050. Nuclear power generation is used at almost the same level as the current usage.
Wind power generation is not so large, but steadily grows in future.
In the halving global CO2 emission scenario, large diffusion of CCS and substantial expansion of nuclear andrenewables (biomass, wind power, PV, etc.) are cost efficient measures for reducing CO2 emissions in 2050.
Wind power generation in the halving global CO2 emission scenario of the ALPS is smaller than that in theBLUE Map scenario of the ETP2010 as mentioned in the previous section. There is no much difference in PV
between the two scenarios. Biomass power generation in the halving global CO2 emission scenario of the ALPS
is larger than that in the BLUE Map scenario of the ETP2010. In addition, CCS is introduced to almost allbiomass power generation in the halving global CO2 emission scenario of the ALPS in 2050. In the halving
global CO2 emission scenario of the ALPS, energy efficiency improvement in energy end-use sector is smaller
than that in the BLUE Map scenario of the ETP2010. Therefore, larger improvements of CO2 intensity in energy
supply sectors are required compared to the ETP2010. For example, greater biomass power generation with CCS
which enables net negative CO2 emissions is required in the ALPS. However, the primary supply of biomass isalmost the same in both the ALPS and the ETP2010 as shown in Figure 5 and Figure 6 because the greater use ofbiomass in the transportation sector, etc. is estimated in the ETP2010.
Figures 8 and 9 show, respectively, renewable electricity generation in 2050 by region for the halving global
CO2 emission scenario of the ALPS and the BLUE Map scenario of the ETP2010. The above mentioned
difference in biomass power generation is observed in Africa and Latin America. For China, PV in the ALPS islarger than that in the ETP2010, but wind power in the ALPS is smaller than that in the ETP2010.
50000
Others
45000

Solar
Wind

Electricity Generration [TWh/yr]

40000

Biomass+CCS
35000

Biomass
Hydro & Geothermal

30000

Nuclear
25000
Gas+CCS
Gas

20000

Oil+CCS
15000
Oil
10000

Coal+CCS
Coal

5000
0Baseline

Halving
global CO2emissions

2030

Baseline

Halving
global CO2emissions

Baseline(ETP2010)

BLUE Map(ETP2010)

2050

Figure 7 Global electricity generation in the Baseline scenario, the halving global CO2 emission
scenario and the BLUE Map scenario

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3.5
3Electricity generation [PWh/yr]

Wind
2.5Solar2

Hydro & Geothermal

1.5Biomass

10.50
OECD Europe United States

AfricaMiddle East

Latin America

China

Figure 8 Renewable electricity generation by region in 2050 for the halving global CO2 emissions

Figure 9 Renewable electricity generation by region in 2050 in the BLUE Map scenario of the IEAETP2010 8)

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Research Institute of Innovative
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2.4 Carbon capture & storage (CCS)
Figures 10 and 11 show captured CO2 by region in the ALPS and the BLUE Map scenario of the IEA ETP2010,respectively. CCS diffusion in early stage will be affected by not only costs but also other uncertain factors.
Therefore, CCS introduction until 2020 is not considered in the model analysis of the ALPS.
If the amount of CO2 storage per site is assumed to be 3MtCO2/yr, the storage sites of 850 are needed in theworld in 2030 in both the scenarios, and those of 3,400 and 4,500 are needed in 2050 in the ETP2010 and theALPS, respectively. Large scale diffusion of CCS will be required for achieving the emission target.

14000
OECD Pacific

12000

OECDUnited States

OECD Europe
Other developing Asia
Middle East

8000

India
Eastern European Union and Former Soviet Union

6000

Non-OECD

Captured CO2 [MtCO2/yr]

Other OECD North America

10000

Central and South America
China

4000

Africa

2000

0
2010

2015

2020

2025

2030
Year

2035

2040

2045

2050

Figure 10 Captured CO2 by region for the halving global CO2 emission scenario

Figure 11 Captured CO2 by region in the BLUE Map scenario of the IEA ETP20108)
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CO2 marginal abatement cost[$/tCO2]

2.5 Emission reduction costs
Figures 12 and 13 show, respectively, the CO2 marginal abatement costs and emission reduction costs per GDP(The emission reduction cost is defined as increase in the global energy systems cost relative to the Baselinescenario.) for the halving global CO2 emission scenario.
The CO2 marginal abatement cost steadily increases and reaches $476/tCO2 in 2050. The CO2 marginal
abatement cost in the BLUE Map of the IEA ETP2010 is $175/tCO2 in 2050 (technology optimism: $200/tCO2 –technology pessimism: $500/tCO2 in the ETP20089)) and the CO2 marginal abatement cost in the ALPS is higher
than that in the ETP2010. This difference is considered to be caused by technology development perspective,
regional resolution (the DNE21+ model: 54 regions, the ETP model: 17 regions), and etc. The emission
reduction cost per GDP also increases and reaches 3% in 2050.
The scenarios with such a high CO2 marginal abatement cost will be very unlikely to be realized in the realworld even in 2050. It seems really difficult to achieve halving global CO2 emissions without almost
inconceivable technology revolution which is not naturally taken into account in the assessment model. It isimportant to plan flexible strategy for climate change with considering more moderate emission reduction targets,
adaptation to climate changes, and etc.

500
450
400
350
300
250
200
150
100
5002000

2010

2020

2030

2040

2050

YearEmission reduction cost per GDP[%]

Figure 12 CO2 marginal abatement costs

3.5
32.5
2
1.5
1
0.50

2000

2010

2020

2030

2040

Year
Figure 13 Emission reduction costs per GDP
82050

Research Institute of Innovative
Technology for the EarthReferences
1) RITE; ALPS project annual report 2007 (in Japanese),
http://www.rite.or.jp/Japanese/h19seikahoukoku/h19ichiran-hyou.htm (2007)
2) RITE; ALPS project annual report 2008 (in Japanese)
http://www.rite.or.jp/Japanese/h20seikahoukoku/h20ichiran-hyou0.html (2008)
3) RITE; ALPS project annual report 2009 (in Japanese)
http://www.rite.or.jp/Japanese/h21seikahoukoku/h21ichiran-hyou.html (2009)
4) RITE; ALPS project annual report 2010 (in Japanese)
http://www.rite.or.jp/Japanese/h22seikahoukoku/h22ichiran-hyou.html (2010)
5) RITE; Development of Long-term Socioeconomic Scenarios –Population, GDPhttp://www.rite.or.jp/Japanese/labo/sysken/research/alps/baselinescenario/baselinescenario/E-ScenarioOutlin
e_POPGDP_20110815.pdf (2011)
6) RITE; RITE GHG Mitigation Assessment Model,
http://www.rite.or.jp/Japanese/labo/sysken/about-global-warming/download-data/RITE_GHGMitigationAss
essmentModel_20090529.pdf (2009)
7) K. Akimoto et al., “Estimates of GHG emission reduction potential by country, sector, and cost”, Energy
Policy, Vol.38, Issue 7, pp.3384-3393 (2010)8) IEA, Energy Technology Perspectives 2010 (2010)9) IEA, Energy Technology Perspectives 2008 (2008)

Contact to:
Kohko Tokushige, Fuminori Sano, Keigo Akimoto
Systems Analysis Group
Research Institute of Innovative Technology for the Earth (RITE)
9-2 Kizugawadai, KIzugawa-shi Kyoto 619-0292 JAPAN
PHONE: +81-774-75-2304, FAX: +81-774-75-2317, E-mail：sysinfo@rite.or.jp

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