1.2.1 Some Fundamentals Regarding Greenhouse Gases and Tropospheric Aerosols (see SAR WGI for 8 1.2.2 Stabilization of CO2 Concentrations (see SAR WGI for more details) 8 1.2.3 Taking the Climatic Effects of Other Greenhouse Gases and Aerosols into Account: the Concept of 8 1.2.4 1.2.5 The Global Temperature and Sea Level Implications of Stabilizing Greenhouse Gases 8 9 2.1 2.2 2.2.1 2. Geophysical Implications Associated with Greenhouse Gas Stabilization General Principles of Stabilization: Stabilization of Carbon Dioxide and Other Gases Description of Concentration Profiles, Other Trace Gas Scenarios and Computation of Equivalent CO2 Concentration Profiles Leading to Stabilization 13 13 13 13 13 Emissions Implications of Stabilization of CO2 Concentrations 13 16 2.2.5 2.3 Stabilization of CH4, N2O and Other Gases 2.2.4 Stabilizing Equivalent CO2 Concentration Equivalent CO2 Sensitivities Temperature and Sea Level Consequences of Stabilizing CO2 Concentrations 2.3.1 Temperature and Sea Level Analyses: Methodology 2.3.2 3. Impacts and Mitigation Costs Associated with Stabilizing Greenhouse Gases Impacts Associated with Different Emissions Trajectories 16 18 19 21 23 23 Implications of Stabilization of Greenhouse Gases for Temperature and Sea Level 24 3.2 Mitigation Costs of Stabilizing CO2 Concentrations 3.2.1 3.1 3.2.2 3.2.2.1 3.2.1.3 Cost Differential Between Fossil Fuels and Carbon-free Alternatives Modelling the Costs of Stabilizing CO2 Concentrations Studies Available at the Time of the SAR WGIII 33 34 36 36 1 Temperature and Sea Level Consequences of Stablilization of CO2 Concentrations from 1990 to 2300 2 Glossary of Terms 3 Acronyms and Abbreviations 4 Units 5 Lead Authors' Affiliations 6 List of IPCC Outputs Contents 37 37 37 37 37 38 39 41 43 43 45 49 50 51 52 Preface This Intergovernmental Panel on Climate Change (IPCC) Technical Paper on “Stabilization of Atmospheric Greenhouse Gases: Physical, Biological and Socio-economic Implications" is the third paper in the IPCC Technical Paper series and was produced in response to a request made by the Subsidiary Body for Scientific and Technological Advice (SBSTA) of the Conference of the Parties (COP) to the United Nations Framework Convention on Climate Change (UN/FCCC). Technical Papers are initiated either at the request of the bodies of the COP, and agreed by the IPCC Bureau, or as decided by the IPCC. They are based on the material already in IPCC Assessment Reports and Special Reports and are written by Lead Authors chosen for the purpose. They undergo a simultaneous expert and government review, during which comments on this paper were received from 93 reviewers from 27 countries, followed by a final government review. The Bureau of the IPCC acts in the capacity of an editorial board to ensure that review comments have been adequately addressed by the Lead Authors in the finalization of the Technical Paper. The Bureau met in its Twelfth Session (Geneva, 3-5 February 1997) and considered the major comments received during the final government review. In the light of its observations and requests, the Lead Authors finalized the Technical Paper. The Bureau was satisfied that the agreed Procedures had been followed and authorized the release of the Paper to the SBSTA and thereafter publicly. We owe a large debt of gratitude to the Lead Authors who gave of their time very generously and who completed the Paper at short notice and according to schedule. We thank the Cochairmen of Working Group I of the IPCC, John Houghton and Gylvan Meira Filho who oversaw the effort, the staff of the United Kingdom Meteorological Office graphics studio who prepared the figures for publication, Christy Tidd who assisted the convening Lead Author in the preparation of the paper and particularly David Griggs, Kathy Maskell and Anne Murrill from the IPCC Working Group I Technical Support Unit, for their insistence on adhering to quality and timeliness. B. Bolin Chairman of the IPCC N. Sundararaman Secretary of the IPCC Stabilization of Atmospheric Greenhouse David Schimel, Michael Grubb, Fortunat Joos, Robert Kaufmann, Richard Moss, Wandera Ogana, Richard Richels, Tom Wigley Contributors: Regina Cannon, James Edmonds, Erik Haites, Danny Harvey, Atul Jain, Rik Leemans, Kathleen Miller, Robert Parkin, Elizabeth Sulzman, Richard van Tol, Jan de Wolde Modellers: Michele Bruno, Fortunat Joos, Tom Wigley (c) The deduced emissions for the aforementioned concentra Of the greenhouse gases, this paper focuses on CO2 because it tion stabilization profiles; has had, and is projected to have, the largest effect on radiative forcing. The effects of other greenhouse gases are also consid (d) A consideration of the stabilization of radiative forcing ered and a series of assumptions are made about their potential agents other than CO2; future emissions. Figure 1. Profiles of CO2 leading to stabilization at concentrations from 350 to 1 000 ppmv. For comparison, the pre-industrial concentration was close to 280 ppmv and the current concentration is approximately 360 ppmv. For stabilization at concentrations from 350 to 750 ppmv, two different routes to stabilization are shown: the S profiles (from IPCC94) and the WRE profiles (from Wigley, et al., 1996) which allow CO2 emissions to follow IS92a until the year 2000 or later (depending on the stabilization level). A single profile is defined for 1000 ppmv. These two sets of profiles are merely examples from a range of possible routes to stabilization that could be 1 For a definition of radiative forcing, see Appendix 2. In addition, the effects of aerosols, which act to cool the planet, are considered. Tropospheric aerosols (microscopic airborne particles) resulting from the combustion of fossil fuels, biomass burning, and other anthropogenic sources have led to a negative forcing that is highly uncertain. Because aerosols have short lifetimes in the atmosphere, their distribution and hence immediate radiative effects are very regional in character. Some implications associated with stabilizing greenhouse gases Among the range of CO2 stabilization cases studied, accumulated anthropogenic emissions from 1991 to 2100 fall between 630 and 1410 GtC, for stabilization levels between 450 and 1 000 ppmv. For comparison, the corresponding accumulated emissions for the IPCC IS92 emissions scenarios range from 770 to 2190 GtC. Calculations of CO2 emissions consistent with a range of stabilization levels and pathways are presented using models and input data available and generally accepted at the time of the IPCC Second Assessment Report. Ecosystem and oceanic feedbacks may reduce terrestrial and oceanic carbon storage to levels somewhat below those assumed in the simplified global carbon cycle models used here and in the Second Assessment Report. Uncertainties resulting from the omission of potentially critical oceanic and biospheric processes during climate change could have a significant effect on the conclusions regarding emissions associated with stabilization. |