Emissions Scenarios - IPCC

316 Summary Discussions and Recommendations
(Box 6.4 continued)
median, and none should be interpreted as such. The statistics associated with the frequency distributions of SRES
scenarios do not represent the likelihood of their occurrence. The writing team cautions against constructing a central,
"best-estimate" scenario from the SRES scenarios; instead it recommends use of the SRES scenarios as they are.
• Concerning large-scale climate models, the writing team recommends that the minimum set of SRES scenarios should
include the four designated marker scenarios and the tvi'O additional illustrative scenarios selected from the scenario
groups in the Al family. At the minimum (a) a simulation for one and the same SRES marker or illustrative scenario
should be performed by every TAR clmiate model for a given stabilization ceilmg, and (b) the set of simulations
performed by the TAR climate models and stabilization mns for a given ceiling should mclude all four of the SRES
marker scenarios.
• The driving forces and emissions of each SRES scenario shoidd be used together. To avoid internal inconsistencies,
components of SRES scenarios should not be mixed. For example, the GHG emissions from one scenario and the SOj
emissions from another scenario, or the population from one and economic development path from another, should not
be combined.
• The SRES scenarios can provide policy makers with a long-term context for near-term decisions. This imphes that they
are not necessarily well suited for the analysis of near-term developments. When analyzing mitigation and adaptation
options, the user should be aware that although no additional climate initiatives are included in the SRES scenarios,
various changes have been assumed to occur that would require other policy interventions.
• More detailed information on assumptions, inputs, and the results of the 40 SRES scenarios should be made available at
a web site and on a CD-ROM. Regular maintenance of the SRES web site is
Box 6-5: Recommendations for Consideration by the IPCC
• Extend the SRES web site and CD-ROM to provide, if appropriate, time-dependent geographic distributions of driving
forces and emissions, and concentrations of GHGs and sulfate aerosols.
• Development of a classification scheme for classifying scenarios as intervention or non-intervention scenarios.
• Establish a programme for on-going evaluations and comparisons of long-term emissions scenarios, including a regularly
updated scenario database.
• An effort should be made m the future to develop an appropriate emissions scenario classification scheme.
• Identify resources for capacity building in the area of emissions scenarios for future IPCC assessments, with a particular
emphasis to involve strong participation from developmg countries.
• Promote activities within and outside the IPCC to extend the SRES multi-baseline and multi-model approach in future
assessments of climate change impacts, adaptation, and mitigation.
• Initiate new programs to assess GHG emissions from land use and sources of emissions other than energy-related CO2
emissions, to go beyond the effort of SRES, which was limited by time and resoiffces.
• Initiate new programs to assess future developments of driving forces and GHG emissions for different regions and for
different sectors (taking the set of SRES scenarios as reference for overall global and regional developments) to provide
more regional and sectorial detau than time and resources allowed SRES to achieve.
forces and emissions in 2020, 2050, and 2100. Table 6-2a
summarizes the ranges of the main scenario driving forces:
global population, economic development, per capita income
levels and income ratios, energy intensity, primary energy use,
and stmcture of energy supply. Table 6-2b summarizes the
emissions of GHGs, SO2, and ozone precursors emissions for
the years 2020, 2050, and 2100 as well as cumulative 1990-
2100 CO, emissions broken down into energy- and land-use
related sources. Together, the two tables provide a concise
summary of the new SRES scenarios.