This more complex pattern of future emissions across the range of SRES scenarios, time periods, world regions, and sectors reflects recent scenario literature. Describing potential future developments involves inherent ambiguities and uncertainties. And even for each alternative development path described by any given scenario, there are numerous combinations of driving forces and numeric values that can be consistent with a particular scenario description. The numeric precision of any model result should not distract from the basic fact that uncertainty abounds. However, the multi-model approach increases the value of the SRES scenario set, since uncertainties in the choice of model input assumptions can be separated more explicitly from the specific model behavior and related modeling uncertainties.
Any scenario has subjective elements and is open to various interpretations.
While the writing team as a whole has no preference for any of the scenarios, and has no judgment as to the probability or desirability of different scenarios, the open process and initial reactions to draft versions of this report show that individuals and interest groups do have such judgments. The writing team hopes that this will stimulate an open discussion in the policy making arena about potential futures and choices that can be made in the context of climate change response. The writing teams suggestions for consideration by the IPCC are summarized in Box 6-5 . Finally, the writing team believes that the SRES scenarios largely fulfill all the specifications set out in Chapter 1 . To support reproducibility, more detailed information than can be included in this report will be made available by individual modeling groups and members of the writing team through other means, such as web sites, peer-reviewed literature, or background documentation if additional resources can be made available.