In Sections 1.2 and 1.3, we examined literature that was motivated primarily by concerns of global cost-effectiveness and global equity respectively. We now turn to a third category of literature, which is motivated largely by considerations of global sustainability. This literature views the climate problem as a component of a larger problem, namely the unsustainable lifestyles and patterns of production and consumption, and explores a broad range of options for moving the world towards a sustainable future (Figure 1.6).

The modes of analysis in the studies reviewed in Sections 1.2 and 1.3 start, by and large, with existing institutions and behaviour, and examine their implications for future outcomes. The literature discussed in this section adopts a different approach. It starts with desirable outcomes and examines actions and institutions from the point of view of their compatibility with desirable outcomes. It seeks to fulfil a different objective. It aims to create shared visions of sustainable and desirable societies among the general public, and so it does not, in the first place, suggest implementation alternatives for fixed goals to decision makers (Costanza, 2000). To enlarge the range of accessible options in future decisions, authors who contribute to this line of inquiry intend to foster a process of societal learning among citizens. After all, value formation through public discussion is, as Sen (1995) suggests, the essence of democracy. In doing so, the work of these authors complements the studies discussed above by providing alternative frameworks, normative contexts, and sets of methodological tools to assess (a broader range of) policy options. Conceptually speaking, this literature takes two forms. The first offers visions of the future based on the inter-relation of various factors across a long time-scale. The second explores possible elements of future scenarios, often relying upon the extrapolation of the existing experience with sustainable practices.

The bulk of this literature starts with the recognition that long-term sustainability can imply an appropriate scale of resource flows, in society (Daly, 1997). Taking a society of appropriate physical scale as a desirable future, this literature goes on to works backwards (backcasts) through possible development paths that may lead from present-day society to a more sustainable, and in the case of concerns about climate change, low-carbon society. Authors who write from this perspective usually assume that resource availability, technology, and society move forwards in a co-evolutionary fashion (Norgaard, 1994). They work on the hypothesis that the transition to balanced and sustainable resource flows implies concomitant changes in technologies, institutions, lifestyles, and worldviews. Though this research takes a certain state of sustainability as its point of departure, it is also sensitive to the principles of equity and cost-effectiveness. It tends to view these as second-order principles that provide structure to the pursuit of sustainability, the first-order principle. In a sense, this literature can be viewed as the mirror image of the studies reviewed earlier–studies that justify the pursuit of sustainability on the grounds of efficiency and equity.

This perspective becomes relevant when it is placed in the context of concernsabout unsustainability (loss of biological diversity, extinction of species, air and water pollution, deforestation, desertification, persistent poverty, and rising inequality both within and between nations, and so on). These concerns are derived from underlying pressures imposed by the growth of consumption and population and the inability of many people and communities to protect their health and livelihoods against these damages. Climate change is thus a potentially critical factor in the larger process of society’s adaptive response to changing historical conditions through its choice of developmental paths (Cohen et al., 1998, p. 360). Chapter 2 of this report (based on the IPCC (2000a) Special Report on Emissions Scenarios (SRES)) notes, for example, that future emissions will be determined not just by climate policy, but also and more importantly by the “world” in which we will live. Decisions about technology, investment, trade, poverty, biodiversity, community rights, social policies, or governance, which may seem unrelated to climate policy, may have profound impacts upon emissions, the extent of mitigation required, and the cost and benefits that result. Conversely, climate policies that implicitly address social, environmental, economic, and security issues may turn out to be important levers for creating a sustainable world (Reddy et al., 1997, p. 6).

Backcasting from desirable future conditions can, according to Thompson et al. (1986), be a useful response to situations characterized by a high degree of ignorance, for which it is difficult to assess the probabilities of possible outcomes or even to know what those possible outcomes might be. Although there is a scientific consensus that anthropogenic climate change is occurring, there is considerable uncertainty about the rate of expected change and its manifestations and impacts at the regional and global levels (see IPCC, 2001, Chapter 19). Science cannot predict the climate and its impacts in Milwaukee, Mumbai, or Moscow half a century ahead very accurately, and it may never be able to do so. Moreover, these types of predictions also require scenarios of the social, economic, and technological paths that the world will follow over the same period (see Chapter 2)–knowledge that may be further beyond our reach than climate prediction. Moreover, this uncertainty increases with the time scale.

The high degree of uncertainty under which climate policy must be developed has important implications for the type of policy regimes likely to be most effective. There is a high degree of uncertainty about how ecosystems would respond to climate change in the studies reviewed here. This recognition suggests that a portfolio approach that includes a broad range of policies diversified across all the major uncertainties might be better than betting on any one particular set of outcomes. Some studies have even drawn a direct parallel between the value of biological diversity and the diversity of institutions and worldviews that contribute to the social capital necessary to maintain the sustainability of human societies (Rayner and Malone, 1998b). Stressing the relationship between risk, resilience, and governance, these authors argue that rather than seeking to anticipate and fix particular problems, the purpose of policy should be to develop coping capacity. This would both switch development and environmental management strategies more nimbly as scientific information improves and strengthen the resilience of vulnerable communities to climate impacts. Conditions of deep uncertainty make it rational for societies to focus on increasing their resilience and flexibility. Resilience in the face of unknown challenges, this research argues, may be achieved by relying on the formation of values and worldviews that embrace the goal of long-term sustainability, at least until some of the key uncertainties are resolved to the point that pursuit of a more narrowly focused policy regime can be justified.

Backcasting from a sustainable future state also supports the search for options with which certain normative goals might be achieved. For climate mitigation scenarios, such a goal might be expressed as a hypothetically acceptable stabilization threshold for GHG concentrations that may, in turn, imply certain trajectories for emission reductions. At this point, therefore, it is useful to review the historical data of global and regional carbon emissions in aggregate as well as in per capita terms (Table 1.1; see also Box 1.1 on the controversy over presentation of data). In 1996, aggregate global emissions were about 6GtC, that is about 1 tonne of carbon per capita world-wide. Of this, the 1.2 billion people living in Annex I countries emitted roughly 64% (3.8GtC), or an average of about 3 tonnes of carbon per capita (3tC/capita). In contrast, 4.4 billion people living in non-Annex I countries were responsible for the remaining 2.1GtC, averaging only 0.5tC/capita, or about one-sixth the average for richer countries. Global emissions increased from 5.8GtC to 6GtC from 1990 to 1996, and are projected to increase to 6.4GtC in 2000 and 9.8GtC in 2020.²² Non-Annex I emissions are growing much faster than those of Annex I countries, averaging 3.5% annual growth compared with 1% in Annex I. As a result, the Annex I share of emissions is declining–from approximately 72% in 1990 and 64% in 1995 to a projected 50% in 2020.

Table 1.2 provides long-term information by displaying aggregate emissions budgets for IPCC SRES scenarios (IPCC, 2000a) and for various stabilization goals identified in the SAR (IPCC, 1996). These goals translate into a 100-year emissions “budget” of 630GtC–13,00GtC. As discussed in Section 1.3.1, the target of 450ppmv translates into a reduction (by 2100) of annual emissions to about 3GtC; that is reductions in annual emissions to half of the current level of about 6GtC. Simply stated, per capita emissions of all countries have to fall below current levels in developing countries if GHG stabilization at low levels is to be the targetted future. If these reductions were shared equally, per capita emissions of developed countries would decline by a factor of 10, while emissions from developing countries would halve²³.

All of these scenarios proceed on the premise that economic growth (at least as currently measured) is not the sole goal of societies across the globe. Moreover, they assume that the relationships between economic growth and resource consumption, on the one hand, and wellbeing, on the other, are not fixed. Both should, instead, be shapable by political and social design. A given level of gross domestic product (GDP) can be achieved with different resource flows (Adriaanse et al., 1997),²⁴ and economic growth that takes societies beyond certain subsistence levels may not increase satisfaction, or human welfare (UNDP, 1998), or societal welfare (Cobb and Cobb, 1994; Linton, 1998). Consequently, the purpose of these visions is to explore how societies might be able to decouple economic output from resource flows (see Weizsäcker et al., 1997; OECD, 1998) and wellbeing from economic output (see Robinson and Herbert, 2000). Climate change mitigation is one of the co-benefits of these decoupling processes.

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