Chapter 2: Greenhouse Gas Emission Mitigation Scenarios and Implications
Executive Summary
Global Futures Scenarios Global futures scenarios do not specifically or uniquely consider GHG emissions. Instead, they are more general “stories” of possible future worlds. They can complement the more quantitative emission scenario assessment because they consider dimensions that elude quantification, such as governance and social structures and institutions, but which are nonetheless important to the success of mitigation policies. Addressing these issues reflects the different perspectives presented in Chapter 1 on cost-effectiveness, equity, and sustainability.
A survey of this literature has yielded a number of insights. First, a wide range of future conditions has been identified by futurists, ranging from variants of sustainable development to collapse of social, economic, and environmental systems. Since the underlying socio-economic drivers of emissions may vary widely in the future, it is important that climate policies should be designed so that they are resilient against widely different future conditions.
Second, the global futures scenarios that show falling GHG emissions tend to show improved governance, increased equity and political participation, reduced conflict, and improved environmental quality. They also tend to show increased energy efficiency, shifts to non-fossil energy sources, and/or shifts to a post-industrial economy. Furthermore, population tends to stabilize at relatively low levels, in many cases as a result of increased prosperity, expanded provision of family planning, and improved rights and opportunities for women. A key implication is that sustainable development policies can make a significant contribution to emission reduction.
Third, different combinations of driving forces are consistent with low emission scenarios. The implication of this would seem to be that it is important to consider the linkage between climate policy and other policies and conditions associated with the choice of future paths in a general sense.
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2.3 Greenhouse Gas Emissions: General Mitigation Scenarios
Global futures scenarios do not specifically or uniquely consider GHG emissions. Instead, they are more general “stories” of possible future worlds. They can complement the more quantitative emissions scenario assessments, because they consider dimensions that elude quantification, such as governance and social structures and institutions, but which are nonetheless important to the success of mitigation policies. Addressing these issues reflects the different perspectives presented in Section 1: cost-effectiveness and/or efficiency, equity, and sustainability.
A survey of this literature has yielded a number of insights that are relevant to GHG emissions scenarios and sustainable development. First, a wide range of future conditions has been identified by futurists, ranging from variants of sustainable development to collapse of social, economic, and environmental systems. Since future values of the underlying socio-economic drivers of emissions may vary widely, it is important that climate policies should be designed so that they are resilient against widely different future conditions.
Second, the global futures scenarios that show falling GHG emissions tend to show improved governance, increased equity and political participation, reduced conflict, and improved environmental quality. They also tend to show increased energy efficiency, shifts to non-fossil energy sources, and/or shifts to a post-industrial (service-based) economy; population tends to stabilize at relatively low levels, in many cases thanks to increased prosperity, expanded provision of family planning, and improved rights and opportunities for women. A key implication is that sustainable development policies can make a significant contribution to emission reduction.
Third, different combinations of driving forces are consistent with low emissions scenarios, which agrees with the SRES findings. The implication of this seems to be that it is important to consider the linkage between climate policy and other policies and conditions associated with the choice of future paths in a general sense.
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2.4 Global Futures Scenarios
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2.4.4 Global Futures Scenarios, Greenhouse Gas Emissions, and Sustainable Development
Of the 124 global futures scenarios in the database, 35 provide some kind of projection of future GHG (usually CO2) emissions. These projections range from narrative descriptions (e.g., “emissions continue to rise”) to numerical estimates. Figure 2.9 shows global carbon dioxide emissions projections from the scenarios that provide numerical estimates.
Most (22) of these scenarios project increased emissions, but several (13) foresee declining emissions. All but one of the latter scenarios are Sustainable Development scenarios in which there is a concerted policy effort towards emission reduction, innovation in energy development towards improved efficiency and conservation, and/or alternatives to fossil fuels. The exception is a High-Tech Optimist scenario in which energy efficiency technologies and a shift to low- and non-fossil fuels bring about declining emissions.
The Sustainable Development scenarios that project declining emissions are in general characterized by increased co-operation and political participation; many assume that there is strong international agreement on the environment and development in general and climate change in particular. There is improved environmental quality and equity and, in several scenarios, increased material affluence globally (although some scenarios indicate a decline in consumerism). Population continues to grow but at slower rates and stabilizes at relatively low levels. In most scenarios significant developments of energy efficiency, energy conservation, and alternative energy technologies are key to emission reduction; a number of scenarios assume a tax on fossil fuels.
Table 2.4 summarizes the apparent relationships between emissions and scenario dimensions. It is important to note that there is considerable variety among the scenarios; Table 2.4 therefore shows relationships that were in the majority, but not necessarily all, of the scenarios. It should also be noted that the relationships shown in Table 2.4 do not by themselves prove causation; they simply reflect what the majority of scenarios with rising and falling GHG emissions, respectively, indicate for each scenario dimension.
What is clear from Table 2.4 is that there are no strong patterns in the relationship between economic activity and GHG emissions. Growth in economic activity is compatible, across this set of scenarios, with both increasing and decreasing GHG emissions. In the latter case, mediating factors include increased energy efficiency, shifts to non-fossil energy sources, and/or shifts to a post-industrial (service-based) economy. Similarly, population growth is present in scenarios with rising emissions as well as scenarios with falling emissions, although in the latter group of scenarios, population tends to stabilize at relatively low levels, in many cases owing to increased prosperity, expanded provision of family planning, and improved rights and opportunities for women.
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