Footnotes for Chapter 6: Summary Discussions and Recommendations

1. Included are anthropogenic emissions of carbon dioxide (CO₂ ), methane (CH₄), nitrous oxide (N₂O), hydrofluorcarbons (HFCs), perfluorocarbons (PFCs), sulfur hexafluoride (SF₆), hydrochlorofluorocarbons (HCFCs), chlorofluorocarbons (CFCs), sulfur dioxide (SO₂), carbon monoxide (CO), nitrogen oxides (NOx), and non-methane volatile organic compounds (NMVOCs).

2. During the approval process of the Summary for Policymakers at the 5th Session of Working Group III of the IPCC from 8-11 March 2000 in Katmandu, Nepal, it was decided to combine the A1C and A1G groups into one "fossil intensive" group A1FI in contrast to the non-fossil group A1T, and select two illustrative scenarios from these two A1 groups to facilitate use by modelers and policy makers. This leads to six scenario groups that constitute the four scenario families, three of which are in the A1 family. The six groups all have " illustrative scenarios", four of which are marker scenarios. All scenarios are equally sound. See also Figure SPM-1.

3. This is still true when the two illustrative cases in the A1 family -as selected for the Summary for Policymakers, see footnote 2 - are added.

4. In particular, the IPCC WGI Second Assessment Report (SAR) GWPs are calculated for constant concentrations (Houghton et al., 1996). In long-term scenarios, concentrations may change significantly, as do GWP values. It is unclear how to apply GWPs to long-term scenarios in a meaningful manner. In addition, the GWP approach is not applicable to gases such as SO₂ and ozone precursors.