|Working Group II: Impacts, Adaptation and Vulnerability|
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12.9.4. Impacts for Differing Emissions Scenarios and Stabilization
Quantitative cross-sectoral impact assessments for differing scenarios are not yet available for Australia and New Zealand. Regional impacts will vary nonlinearly with time before and after stabilization of GHG concentrations. Warming will continue to increase after stabilization, but the beneficial effects of CO2 on plants will no longer increase. Moreover, regional patterns of rainfall change, particularly in southern Australian and New Zealand areas, will tend to reverse after stabilization of GHGs (see Section 18.104.22.168). These complexities, together with the continuing post-stabilization rise in sea level, mean that estimated impacts at the time of stabilization may not be sufficient to determine whether the level of stabilization is a safe one.12.9.5. Uncertainties and Risk Management
Given that some of the climate sensitivities listed in Section 12.9.6, and especially in Table 12-2, already have been observed for natural climate variations (such as El Niño), confidence is high that a range of impacts will occur in Australia and New Zealand as a result of climate change over the coming decades. This level of certainty, and the possibility that the early stages of greenhouse-related changes already may be occurring, justify prudent risk management through initiation of appropriate mitigation and adaptation strategies. Probabilistic assessments of risk, which account for the uncertainties, are regarded as a way forward. These assessments attempt to quantify the various sources of uncertainty to provide a conditional probability of climate change that would cause critical system performance thresholds to be exceeded and require adaptation or result in losses. Stakeholders may define their own subjective levels of acceptable risk and plan accordingly to adapt before or when the threshold is exceeded. Some examples for Australia and New Zealand are presented in this chapter (see Sections 12.5.2, 12.6.1, 12.8.2, and 12.8.4), but more are needed.12.9.6. Vulnerability and Adaptability in Australia and New Zealand
The key regional concerns identified in this chapter regarding vulnerability to climate change impacts are ecosystem uniqueness, isolation, and vulnerability; agricultural commodities and terms of trade; droughts, floods, and water supply; increased coastal and tropical exposure to climate hazards; impacts on indigenous peoples and their involvement in adaptation planning; coral reefs; and Australian alpine areas.
Major expected impacts, vulnerability, and adaptability are summarized in Table 12-2. Note that although Australian and (to a lesser extent) New Zealand farmers have adapted, at least in part, to existing El Niño-related droughts, they depend on good years for recovery. Thus, despite their adaptability, they are quite vulnerable to any increase in the frequency of drought or to a tendency for droughts to last for a longer period. This vulnerability flows through to the rural communities that service them (see Section 12.5.6).
Several of these vulnerabilities are likely to interact synergistically with each other and with other environmental stresses. Moreover, vulnerability is a result of exposure to hazard and capacity to adapt. Thus, vulnerability will be greatly affected by future changes in demography, economic and institutional capacity, technology, and the existence of other stresses.
There have been no rigorous studies for Australia or New Zealand that have taken all of these variables into account. Thus, Table 12-2 is based largely on studies that assume that the society that is being impacted is much like that of today. It should not be assumed, however, that socioeconomic changes in the future necessarily will reduce vulnerability in Australia and New Zealand. Indeed, many existing socioeconomic trends may exacerbate the problems. For instance, the bias toward population and economic growth in coastal areas, especially in the tropics and subtropics, by itself will increase exposure to sea-level rise and more intense tropical cyclones. If such trends are not to increase vulnerability, they will need to be accompanied by a conscious process of planning to reduce vulnerability by other means (e.g., changes in zoning and engineering design criteria). Thus, vulnerability estimates are based on present knowledge and assumptions and can be changed by new developments, including planned adaptation.
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