IPCC Fourth Assessment Report: Climate Change 2007
Climate Change 2007: Working Group III: Mitigation of Climate Change

3.3.6 Characteristics of regional and national mitigation scenarios

Table 3.7 summarizes selected national mitigation scenarios. There are broadly two types of national scenarios that focus on climate mitigation. First, there are the scenarios that study mitigation options and related costs under a given national emissions cap and trade regime. The second are the national scenarios that focus on evaluation of climate mitigation measures and policies in the absence of specific emissions targets. The former type of analysis has been mainly undertaken in the studies in the European Union and Japan. The latter type has been explored in the USA, Canada and Japan. There is also an increasing body of literature, mainly in developing countries, which analyses national GHG emissions in the context of domestic concerns, such as energy security and environmental co-benefits. Many of these developing country analyses do not explicitly address emissions mitigation. In contrast to global studies, regional scenario analyses have focused on shorter time horizons, typically up to between 2030 and 2050.

Table 3.7: National scenarios with quantification up to 2050 and beyond.

Country Author/Agency Model Time horizon Target variables Base year Target of reduction to the value of the base year 
USA Hanson et al. (2004) AMIGA1 2000-2050 2000 (about 44% in 2050) 
Canada Natural Resource Canada (NRCan) (2000) N.A. 2000-2050 GHG emissions 2000 (53% in 2050) 
India Nair et al. (2003) Integrated modelling framework1,3 1995-2100 Cumulative CO2 emissions   550 ppmv, 650 pmv 
Shukla et al. (2006) ERB2 1990-2095 CO2 emissions   550 ppmv 
China Netherlands Chen (2005) MARKAL-MACRO2,3 2000-2050 CO2 emissions Reference 5-45% in 2050 
Van Vuuren et al. (2003) IMAGE/TIMER2,4 1995-2050 GHG emissions 1995 
Jiang and Xiulian (2003) IPAC-emission2,3 1990-2100 GHG emissions 1990 
Tuinstra et al. (2002) (COOL)   1990-2050 GHG emissions 1990 80% in 2050 
Germany Deutscher Bundestag (2002) WI4, IER 2000-2050 CO2 emissions 1990 80% in 2050 
UK Department of Trade and Industry (DTI) (2003) MARKAL3 2000-2050 CO2 emissions 2000 45%, 60%, 70% in 2050 
France Interministerial Task Force on Climate Change (MIES) (2004) N.A. 2000-2050 CO2 emissions 2000 0.5 tC/cap (70% in 2050) 
Australia Ahammad et al. (2006) GTEM1 2000-2050 GHG emissions 1990 50% in 2050 
Japan Japan LCS Project (2005) AIM/Material1 MENOCO4 2000-2050 CO2 emissions 1990 60-80% in 2050 
Ministry of Economy, Trade and Industry (2005) GRAPE3 2000-2100 CO2/GDP 2000 1/3 in 2050, 1/10 in 2100 
Masui et al. (2006) AIM/Material1 2000-2050 CO2 emissions 1990 74% in 2050 
Akimoto et al. (2004) Optimization model3 2000-2050 CO2 emissions 2000 0.5% /yr (21% in 2050) 
Japan Atomic Industrial Forum (JAIF) (2004) MARKAL3 2000-2050 CO2 emissions 2010 (1990) 40% in 2050 
Notes: model types: 1: CGE-type top-down model, 2: other type of top-down model, 3: bottom-up technology model with optimization, 4: bottom-up technology model without optimization.  

A number of scenario studies have been conducted for various countries within Europe. These studies explore a wide range of emission caps, taking into account local circumstances and potentials for technology implementation. Many of these studies have used specific burden-sharing allocation schemes, such as the contraction and convergence (C&C) approach (GCI, 2005) for calculating the allocation of worldwide emissions to estimate national emissions ceilings. The UK’s Energy White Paper (DTI, 2003) examined measures to achieve a 60% reduction in CO2 emissions by 2050 as compared to the current level. Several studies have explored renewable energy options, for example, the possibility of expanding the share of renewable energy and the resulting prospects for clean hydrogen production from renewable energy sources in Germany (Deutscher Bundestag, 2002; Fischedick and Nitsch, 2002; Fischedick et al., 2005). A European study, the COOL project (Tuinstra et al., 2002; Treffers et al., 2005), has explored the possibilities of reducing emissions in the Netherlands by 80% in 2050 compared to 1990 levels. In France, the Inter Ministerial Task Force on Climate Change (MIES, 2004) has examined mitigation options that could lead to significant reductions in per capita emissions intensity. Savolainen et al. (2003) and Lehtila et al. (2005) have conducted a series of scenario analyses in order to assess technological potentials in Finland for a number of options that include wind power, electricity-saving possibilities in households and office appliances, and emission abatement of fluorinated GHGs.

Scenario studies in the USA have explored the implications of climate mitigation for energy security (Hanson et al., 2004). For example, Mintzer et al. (2003) developed a set of scenarios describing three divergent paths for US energy supply and use from 2000 through 2035. These scenarios were used to identify key technologies, important energy policy decisions, and strategic investment choices that may enhance energy security, environmental protection, and economic development.

A wide range of scenario studies have also been conducted to estimate potential emissions reductions and associated costs for Japan. For example, Masui et al. (2006) developed a set of scenarios that explore the implications of severe emissions cutbacks of between 60 and 80% CO2 by 2050 (compared to 1990). Another important study by Akimoto et al. (2004) evaluates the possibilities of introducing the CCS option and its economic implications for Japan.

National scenarios pertaining to developing countries such as China and India mainly analyze future emission trajectories under various scenarios that include considerations such as economic growth, technology development, structure changes, globalization of world markets, and impacts of mitigation options. Unlike the scenarios developed for the European countries, most of the developing-country scenarios do not specify limits on emissions (Van Vuuren et al., 2003; Jiang and Xiulian, 2003). Chen (2005) shows that structural change can be a more important contributor to CO2 reduction than technology efficiency improvement. The scenario construction for India pays specific attention to developing-country dynamics, underlying the multiple socio-economic transitions during the century, including demographic transitions (Shukla et al., 2006). Nair et al. (2003) studied potential shifts away from coal-intensive baselines to the use of natural gas and renewables.

There are several country scenarios that consider drastic reduction of CO2 emissions. In these studies, which consider 60–80% reductions of CO2 in 2050, rates of improvement in energy intensity and carbon intensity increase by about two to three times their historical levels (Kawase et al., 2006).

Table 3.8 summarizes scenarios with more than 40% CO2 reductions (2000–2050) in several developed countries. The table also includes some Chinese scenarios with deep cuts of CO2 emissions compared to the reference cases. Physical indicators of the Chinese economy show that current efficiency is below the OECD average in most sectors, thus indicating a greater scope for improvement (Jiang and Xiulian, 2003). It should be noted that comparing the energy intensity of the Chinese economy on the basis of market exchanges rates to OECD averages suggests even larger differences, but this is misleading given the differences in purchasing power (PPP-corrected energy intensity data gives a somewhat better basis for comparison, but still suffers from uncertainty about the data and different economic structures).

In the countries with low energy intensity levels in 2000 (such as Japan, Germany and France), the scenarios specify solutions for meeting long-term drastic reduction goals by carbon intensity improvement measures, such as shifting to natural gas in the UK, renewable energy in the Netherlands, and CCS in certain scenarios in France, Germany, the UK and the USA. France has a scenario where CCS accounts for 100% of carbon intensity improvement. Most of the scenarios with drastic CO2 reductions for the USA and the UK assume the introduction of CCS.

The light yellow coloured area in Table 3.8 shows the range of the global model results of EMF-21 with the stabilization target of 4.5 W/m2. Most country results show the need for greater improvement in carbon intensity during 2000 to 2050 compared to the global results. The results of scenario analysis since the TAR show that energy intensity improvement is superior to carbon intensity reduction in the first half of the 21st century, but that carbon intensity reduction becomes more dominant in the latter half of the century (Hanaoka et al., 2006).

Table 3.8: Developed countries scenarios with more than 40% reduction (compared to 2000 emissions), and some Chinese scenarios: CO2 emission changes from 2000 to 2050; Energy intensity and carbon intensity in 2000, and their changes from 2000 up to 2050.

(A) CO2 emission changes, energy intensity, and carbon intensity in 2000.

(B) Changes in energy intensity and carbon intensity.

Table 3.8

Notes: Data sources: China: Jiang and Xulian (2003), Van Vuuren et al. (2003), Japan: Masui et al. (2006), Akimoto et al. (2004), JAIF (2004), Germany: Deutscher Bundestag (2002), France: MIES (2004), UK: DTI (2003), USA: Hanson et al. (2004). The coloured areas show the range of the global model results of EMF-21 with the target of 4.5 W/m2. The range of EU-15 is shown for European countries