Environmental Engineering Reference
In-Depth Information
4.2. Projections with A2 scenario and emission reductions
SRES emission estimates for the OECD90 region under the A2-ASF scenario for
the year 2050 indicates a 33.3% increase of NOx, 16.2% increase of VOC and
12.4% decrease of CO from the 2000 emissions. TAPM-CTM was run for the
decade 3 with the GMR anthropogenic emissions inventory scaled by these factors.
The results show that the number of exceedence cell-days decreases slightly (4%)
compared to the base case 2051-2060 scenario for 1-h average ozone and increase
slightly (7%) for the 4-h average ozone. The mixed result for 1- and 4-h ozone
likely reflects the response of the modelled chemistry to increasing NO
x
con-
centrations.
To investigate the level of reduction required to achieve compliance with the
NEPM standards for ozone in the GMR for the climate change scenario, it was
attempted for the decade 3 meteorological scenario by selecting months from this
decade which contain the ten highest 4-h ozone concentrations and then running
emission reduction scenarios in which all anthropogenic precursor emissions were
uniformly reduced by 40% and 70%. The projection with a 40% reduction in
anthropogenic precursor concentrations is estimated to reduce peak 1-h ozone by
17% and peak 4-h ozone by 8% compared to the base case 2051-2060 scenario.
A 70% reduction is estimated to reduce peak 1- and 4-h ozone by 36% and 25%,
respectively. These results support the statement above that the 4-h ozone is more
challenging to reduce than the 1-h concentrations. The results also suggest that an
equal reduction strategy for all of the precursors may not be optimal given that
peak ozone concentrations are still modelled to exceed the NEPM standards even
for emission reductions of 70%.
5. Limitations and Future Directions
(1) As noted earlier, this study is based on a single A2 SRES emissions scenario
and a small suite of GMR anthropogenic emission scenarios. An important area of
future work lies in the generation of ensembles of downscaling results based on
alternative IPCC SRES emission scenarios, based on the climatologies of different
GCMs, and potentially based on different downscaling methodologies. (2) The
current project did not take account for bushfire impacts on ozone and aerosols.
With the likely increase in bushfires, their impact should be considered in future
ozone and climate impact modelling. (3) Changes in background ozone and other
precursor species concentrations due to climate change and due to increases in
global emission should be considered in future work. (4) This project is restricted
to the consideration of gas phase processes. For future work, fine particles should
be included since the largest air pollution health impacts and health costs in
Australia are associated with fine particles.
