^a The uncertainties in the SRES emissions for non- CO₂ greenhouse gases are generally greater than those for energy CO₂ . Therefore, the ranges of non- CO₂ GHG emissions provided in the Report may not fully reflect the level of uncertainty compared to CO₂ , for example only a single model provided the sole value for halocarbon emissions.

^b In the SPM the emissions of CFC/ HFC/ HCFC, PFC, and SF₆ are presented as carbon- equivalent emissions. This was done by multiplying the emissions by weight of each substance (see Table 5- 8) by its global warming potential (GWP; see Table 5- 7) and subsequent summation. The results were then converted from CO₂ -equivalents (reflected by the GWPs) into carbon- equivalents. Note that the use of GWP is less appropriate for emission profiles that span a very long period. It is used here, in the interest of readability of the SPM in preference to a more detailed breakdown by the 27 substances listed in Table 5- 7. The method here is also preferred over the even less desirable option to display weighted numbers for the aggregate categories in this table.