The SRES emissions scenarios also have different emissions for
other GHGs and chemically active species such as CO, NOx , and
volatile organic compounds. The uncertainties that surround the
emissions sources of these gases, and the more complex set of
driving forces behind them are considerable and unresolved.
Hence, model projections of these gases are particularly
uncertain and the scenarios presented here are no exception.
Improved inventories and studies linking driving forces to
changing emissions in order to improve the representation of
these gases in global and regional emission models remain an
important future research task. The emissions of other gases
follow dynamic patterns much like those shown in Figure TS-7 for
carbon dioxide emissions. Further details about GHG emissions
are given in Chapter 5. Some models of the six SRES models do
not provide a comprehensive description of NOx emissions or
include only specific sectors (e.g., energy-related sources) and
have adopted other source categories f