It can be concluded generally that, since SAR (IPCC, 1996a, 1996b) was published, much progress has been achieved in the development of consistent and transparent approaches to assess climate change mitigation costs. This has facilitated understanding of the differences in mitigation cost results generated by different modelling approaches, based on different assumptions. A number of new research topics have been considered particularly important in the establishment of more information about globally efficient and fair climate change mitigation policies. These issues include a better understanding of the relationship between economic costs of climate change mitigation policies and the sustainable development implications in different parts of the world. Specifically, a number of key research issues for further work include:

• Development and application of methodological approaches for the integrated assessment of linkages between climate change mitigation costs and sustainable development, including development, environment, and social dimensions:
  
  • assessment of macroeconomic impacts using different welfare measures,
    
  • co-benefit studies, and
    
  • assessment of equity impacts (intragenerational equity impacts should be represented as detailed studies of distributional impacts, and can be integrated as formal decision criteria in policy assessments).
    
• Development of a framework for the assessment of intra- and intergenerational equity aspects of climate change mitigation studies.
  
• Integration of environmental impact assessments in climate change mitigation studies. This will require the development of consistent methodological approaches and empirical studies.
  
• Establishment of approaches to conduct implementation cost analysis in both top-down and bottom-up models.
  
• Implementation cost studies that reflect financial market conditions, institutional and human capacities, information requirements, market size and opportunities for technology gain and learning, economic incentives, and policy instruments.
  
• Development of a systematic approach for reporting baseline assumptions and the costs of moving from one specific baseline case to a climate change mitigation policy.
  
• Further development of a consistent analytical structure and a format for reporting the main assumptions that underlie costing results, including:
  
  • main scenario drivers: economic growth, technological development, sectoral activity, and fuel prices;
    
  • behavioural assumptions;
    
  • flexibility of climate change mitigation policies, including timing of the reduction policies, GHG emissions included, and international co-operative mechanisms; and
    
  • assumptions about tax recycling options, side-impacts of climate change mitigation policies, and the potential implementation of no regrets options.
    
• Development of approaches to and conduct of studies for developing countries and EITs that better reflect the specific characteristics of these economies in implementing climate change mitigation policies. Some of the major research topics are:
  
  • assessment of alternative development patterns and their relationship to development, social, and environmental sustainability dimensions;
    
  • macroeconomic studies that consider structural adjustment policies and market transformation processes;
    
  • studies of the informal sector and implications for GHG emissions and reduction policies;
    
  • non-commercial energy use; and
    
  • specific implementation policy issues.
    
• Estimates of future costs and sustainability implications that both reflect how climate change might affect future ecosystems, how these altered ecosystems might affect the demand for different goods, and how this demand might affect the welfare of our descendants.

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