Climate Change 2001: Synthesis Report


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Integrating Near- and Long-Term Considerations

  
7.30
Climate change decision making is a sequential process under uncertainty. Decision making at any point in time entails balancing the risks of either insufficient or excessive action.

  
7.31
Development of a prudent risk management strategy involves careful consideration of the consequences (both environmental and economic), their likelihood, and society's attitude toward risk. The latter is likely to vary from country to country and perhaps even from generation to generation. This report therefore confirms the SAR finding that the value of better information about climate change processes and impacts and society's responses to them is likely to be great. Decisions about near-term climate policies are in the process of being made while the concentration stabilization target is still being debated. The literature suggests a step-by-step resolution aimed at stabilizing greenhouse gas concentrations. This will also involve balancing the risks of either insufficient or excessive action. The relevant question is not "what is the best course for the next 100 years," but rather "what is the best course for the near term given the expected long-term climate change and accompanying uncertainties."
7.32
Stabilizing atmospheric concentrations would depend upon emissions reductions beyond those agreed to in the Kyoto Protocol. Most post-SRES scenario analyses suggest that achievement of stabilization at 450 ppmv may require emission reductions during the period 2008 to 2012 in Annex I countries that are significantly stronger than the Kyoto Protocol commitments. This analysis also suggests that achieving the aggregate Kyoto commitments may be consistent with trajectories that achieve stabilization at 550 ppmv or higher. Other analyses suggest a more gradual departure from emissions baselines even for 450 ppmv followed by sharper reductions in subsequent budget periods. The path is influenced by the representation of inertia in the system and expectations about how initial reductions by Annex I countries may relate to the strength and scope of emissions limitation in subsequent periods.
7.33
Climate change mitigation raises both inter-regional and inter-temporal equity considerations.

  
7.34

Differences in the distribution of technological, natural, and financial resources among and within nations and regions, and between generations, as well as differences in mitigation costs, are often key considerations in the analysis of climate change mitigation options. Much of the debate about the future differentiation of contributions of countries to mitigation and related equity issues also considers these circumstances.22 The challenge of addressing climate change raises an important issue of equity, namely the extent to which the impacts of climate change or mitigation policies ameliorate or exacerbate inequities both within and across nations and regions, and between generations. Findings with respect to these different aspects of equity include:

  • Equity within nations: Most studies show that the distributional effects of a carbon tax are regressive unless the tax revenues are used either directly or indirectly in favor of the low-income groups; the regressive aspect can be totally or partially compensated by a revenue-recycling policy.
  • Equity across nations and regions: Greenhouse gas stabilization scenarios assessed in this report assume that developed countries and countries with economies in transition limit and reduce their greenhouse gas emissions first.23 Another aspect of equity across nations and regions is that mitigation of climate change can offset inequities that would be exacerbated by the impacts of climate change (see Question 6).
  • Equity between generations: Stabilization of concentrations depends more upon cumulative than annual emissions; emissions reductions by any generation will reduce the need for those by future generations.24 Inter-generational equity can be promoted by reducing climate change impacts through mitigation of climate change by any generation, since not only would impacts -- which are expected to affect especially those with the fewest resources --
    be reduced, but also subsequent generations will have less climate change to adapt to (see Question 6).
 

Figure 7-5: Carbon in oil, gas, and coal reserves and resources is compared with historic fossil-fuel carbon emissions over the period 1860–1998, and with cumulative carbon emissions from a range of SRES scenarios and TAR stabilization scenarios until the year 2100. Data for current reserves and resources are shown in the lefthand columns. Unconventional oil and gas includes tar sands, shale oil, other heavy oil, coal bed methane, deep geopressured gas, gas in aquifers, etc. Gas hydrates (clathrates) that amount to an estimated 12,000 Gt C are not shown. The scenario columns show both SRES reference scenarios as well as scenarios that lead to stabilization of CO2 concentrations at a range of levels. Note that if by the year 2100 cumulative emissions associated with SRES scenarios are equal to or smaller than those for stabilization scenarios, this does not imply that these scenarios equally lead to stabilization.

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