IPCC Special Report on Emissions Scenarios Intergovernmental Panel on Climate Change

Footnotes for Chapter 2: An Overview of the Scenario Literature

1. The IS92 scenarios have also been analyzed with regard to short-term adequacy (see Gray, 1998).

2. As defined in UNFCCC, 1992.

3. CO2 = (CO2 /E) (E/GDP) (GDP/P) P, where E represents energy consumption, GDP the global domestic product (or global value added) and P population. Changes in CO2 emissions can be described by changes in these four factors or driving forces.

4. The 1990 emissions from energy production and use are estimated by Marland et al. (1999) at 5.9 GtC excluding cement production. It appears as if four scenarios also include deforestation, which might explain relatively large differences in the base-year emissions compared to the other scenarios. Excluding these four scenarios, the 1990 base-year values in the scenarios reviewed range from 4.8 to 6.4 GtC. With the four scenarios the range is from 4.8 to 7.4 GtC.

5. Some of the scenarios may also include CO2 emissions from industrial sources. Since non-energy-related industrial emissions are very low compared to the energy-related CO2 emissions, their impact on the results of the statistical analyses is negligible. It also appears as if four scenarios also include deforestation. These scenarios tend to cluster around the median and none occur in the tails of the scenario frequency distribution. Therefore, they have very little influence on the range.

6. The issue of large differences in the base year quantifications across the range of scenarios is discussed in Chapter 4, in which are presented the new SRES scenarios as developed by six different modeling approaches utilizing different base-year specifications.

7. Not all 256 scenarios that report global CO2 emissions cover the whole period to the year 2100.

8. Carbon sequestration exceeds carbon emissions in the negative emission scenarios.

9. Values are shown also as indexed to 1990 values, since model base years and base-year values differ.

10. Note that the highest scenario in the database reports 3400 EJ for primary energy consumption by 2100. Relative to the base year of this scenario (340 EJ), this level corresponds to a 10-fold increase. However, relative to the base-year value including non-commercial biomass (370 EJ), this level corresponds to a nine-fold increase only.