potential-impacts-of-climate-change-on-the-swan-and-canning-rivers

Table 4 CO 2
stabilisation equivalents <strong>of</strong> SRES scenarios
CO 2
stabilisation equivalents <strong>of</strong> SRES scenarios
SRES scenario Approximate CO 2
equivalent at 2100*
B1 600 (~550)
A1T 700
B2 800
A1B 850
A2 1250
A1F1 1550
*Approximate CO 2
equivalent concentrations ppm corresponding to the computed radiative forcing
due to anthropogenic greenhouse gases and aerosols in 2100.
Data source: IPCC (2007b)
In the opinion <strong>of</strong> the Technical Advisory Panel, in the spectrum <strong>of</strong> emissions scenarios outlined
above, the A2 and B1 scenarios, for adaptation planning represent emissions tracks that are not extreme
among the SRES scenarios. Rather, they can be considered as relatively realistic scenarios
<strong>of</strong> GHG concentration outcomes consistent with:
• fragmented and weakly effective global responses (A2); or
• highly effective global responses aimed at achieving ‘safe’ levels <strong>of</strong> stabilisation (B1).
The implied political failure under an A2 stabilisation level is not so extreme as to imply continuation
<strong>of</strong> business-as-usual growth. In the B1 level stabilisation scenario, global action is not so strong as
to achieve assured avoidance <strong>of</strong> dangerous levels.
In forming judgements on the ‘realism’, ‘optimism’ or ‘pessimism’ <strong>of</strong> these scenarios it is important
to note that, since establishment <strong>of</strong> the SRES scenarios in 2000, the global emissions outcomes
have been tracking at the most extreme <strong>of</strong> the SRES scenarios, i.e. A1F1 (rapid growth under fossil
fuels). As each year passes, the emissions reductions necessary to stabilise cumulative greenhouse
gas concentrations below dangerous levels becomes more and more challenging for the global
community. If stabilisation is to be achieved, the window <strong>of</strong> opportunity is small.
The next few decades are anticipated to be representative <strong>of</strong> high emission scenarios before, optimistically,
very vigorous and highly effective global emissions reductions ‘kick-in’, bringing stabilisation
in latter parts <strong>of</strong> the century. This reasoning suggests that, for those charged with anticipating
and planning adaptive responses, expectations for the fi rst half <strong>of</strong> this century should be weighted
towards the higher end emission scenarios (A1B, A1F1, A2).
1.4 Global <strong>climate</strong> <strong>change</strong> projections
1.4.1 Air and ocean temperatures
Figure 3 shows the IPCC (2007b) projections <strong>of</strong> global mean surface warming for the three representative
scenarios: A2, A1B and B1. Since the IPCC’s fi rst report in 1990 (IPCC 1990), successive
projections have suggested global average temperature increases <strong>of</strong> between about 0.15° and 0.3°
C per decade for 1990 - 2005. This can now be compared with observed values <strong>of</strong> about 0.2° C per
decade, strengthening confi dence in near-term projections.
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