The Regional Impacts of Climate Change

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4.4. Integrated Analysis of Potential Impacts

Summary: Some preliminary studies of impacts for limited areas or issues have been attempted for the region, but comprehensive integrated analyses are not available. A cross-sector economic costing approach indicates substantial impacts on Australasia's GDP (several percent per annum for a doubling of CO2), but the method involved is subject to considerable criticism. The New Zealand CLIMPACTS and Australian OzClim software packages have been developed as national-scale, integrated assessment methodologies to enable the progressive exploration of sensitivities, impacts, adaptation options, and so forth as knowledge develops.

Research is needed on better climate scenarios; the dynamic responses of ecological systems; impacts on marine, aquatic, and coastal ecosystems; possible changes in the magnitude and frequency of "natural disasters"; impacts on settlements, industries, and health; cross-sector and multinational interactions; and potential adaptations and their ameliorating effects.

In summary, Australia's relatively low latitude makes it particularly vulnerable through impacts on its scarce water resources and on crops presently growing near or above their optimum temperatures, whereas New Zealand-a cooler, wetter, mid-latitude country-may gain some benefit from the ready availability of suitable crops and the likely increased agricultural production. In both countries, however, there is a wide range of situations in which vulnerability is thought to be moderate to high-particularly in ecosystems, hydrology, coastal zones, settlements and industry, and health.

A comprehensive integrated analysis of impacts for the region is not possible at present, mainly because of the large uncertainties in each of the three stages of analysis: first, in the magnitude and direction of change in the climate elements; second, in the estimations of potential impacts for individual components of systems; and third, concerning possible interactions between components. Instead, we discuss preliminary attempts to develop integrated assessment methodologies and present results from two case studies.

Integrated assessments of climate change are attempts to integrate three components or dimensions of the problem (Weyant et al., 1996; IPCC 1996, WG III, Chapter 10):

New Zealand was one of the first countries in the world to carry out such an assessment of the effects of climate change at the national scale, based on the work of expert panels and integrated through a national committee (Mosley, 1990a). In Australia, the idea of integrated climate impact assessments has been developed, to some extent, in the context of climatic variability rather than climate change, to better adapt Australian agriculture to the large year-to-year climatic variability associated with ENSO fluctuations. Collaborative projects involving climatologists, agricultural scientists, rural economists, and stakeholders have led to the development of crop-, farm-, and industry-level models that facilitate the application of ENSO-derived seasonal climate forecasting to improve farm and industry management (Stone et al., 1993; BRS, 1994; Stafford Smith et al., 1994). The ability to better predict and manage this short-term climate variability is itself an important adaptation tool.

Two initial efforts at integrated assessment in Australia are described in Box 4-1, on the impacts of climate change on the management of the scarce water resources of the Macquarie River basin in northern NSW, and in Box 4-2, on the impacts of climate change on the cattle tick.


Box 4-2. Climate Change and Cattle Ticks in Australia: An Integrated Assessment

Sutherst et al. (1996) carried out an integrated assessment of the national socioeconomic impact of climate change on the cattle tick (Boophilus microplus), which is an important parasite of cattle in northern Australia. There is concern that global warming will result in a spread of ticks and an increase in their numbers, as indicated by an earlier study for both New Zealand and Australia (Sutherst et al., 1996). The cattle tick causes losses in productivity through feeding in large numbers and by transmitting a blood pathogen that causes high rates of mortality in nonimmune cattle. The southern limit of the ticks currently is maintained by a quarantine and eradication program at the border between NSW and Queensland, at a cost of several million dollars per year.

A population model of the cattle tick was used first to estimate current national losses of productivity of beef cattle due to the ticks in each part of the country. These impacts were costed using an economic model of the cattle industry, after which the exercise was repeated using the changed climate scenarios derived from the CSIRO9 global climate model (experiment F1, Table 1-1). Potential costs were estimated on the basis that the quarantine line would not be economically sustainable because of the recurrent development of strains of ticks that are resistant to the chemicals used to control them and the increasing difficulty of eradication under more favorable climatic conditions.

The maps in the accompanying graphic illustrate the estimated potential costs under current and 2070 climate scenarios. The number of ticks was estimated to increase in the southern part of the existing range-where they are limited by the shortness of the warm season, which allows reproduction, and by severe winter mortality. Both of these constraints were reduced by global warming; as a result, most of the estimated increases in costs would be sustained within the current tick-infested area in Queensland. There was a parallel increase in the potential area affected by ticks in NSW. The final estimates of potential national costs, in terms of net present value, ranged from A$18 million to A$192 million, but these estimates will vary with discount rates.

The analysis was unique in Australia in that it was one of the first to use a fully integrated hierarchical approach to assessing impacts of climate change on pests, diseases, and weeds, including climate change scenarios generated by CSIRO; simulation of the target species (ticks) with a population model; and calculation of economic impacts on the national beef industry, estimated using a beef industry model developed by the Australian Bureau of Agricultural and Resource Economics. To achieve these objectives, an interdisciplinary team of climate modellers, ecologists, and economists was needed. The results are available at http://www.modeling.ctpm.uq.edu.au/dest_public/ on the World Wide Web.

Estimated costs of cattle tick, in Australian dollars per head of cattle, for current (left panel) and 2070 (right panel) climate, using a three-level integrated approach composed of climate scenario, tick/cattle model, and economic model of the national beef industry.

These integrated assessments in Australia and New Zealand are subject, however, to large uncertainties arising from continually evolving GCM-based scenarios of regional climate change. Indeed, the remarkable contrast between the rainfall change scenarios for Australia (and also by implication for New Zealand-see Section 4.2.3) emerging from simulations using slab-ocean GCMs and from the more comprehensive coupled-ocean models (Whetton et al., 1996a) has increased the uncertainty regarding the "correct" scenario to use in impact analyses (CSIRO, 1996a) and has thrown considerable doubt on the predictions of many early impact studies (though they remain valuable as sensitivity studies). As a consequence, there is a growing recognition that integrated assessments for Australia and New Zealand need to be carried out within a versatile framework that allows the range of uncertainties to be explored and the effects of changing scenarios (due to scientific, economic, or policy changes) to be readily assessed in an iterative fashion. For this approach, integrated models are required.

Methods for integrated assessment have been explored at several recent workshops involving Australian and New Zealand participants (Pittock and Mitchell, 1994; Braaf et al., 1995; Hennessy and Pittock, 1996a, b). In New Zealand, a major research program known as CLIMPACTS has been under way since 1993, involving more than seven different laboratories (Kenny et al., 1995; Warrick et al., 1996). This project has coupled the MAGICC model (Wigley, 1994)-which generates a global average warming curve for given input assumptions-to a regional pattern of climate change per 1C global warming, which is based on a range of GCM simulations and local statistical interpolation techniques. A number of impacts models are now being coupled to this framework, in order to examine the sensitivity of the New Zealand environment to climate variability and change. First-order impacts and sensitivities have been assessed for grain maize, pasture, wheat, and kiwifruit.

In Australia, CSIRO has begun developing an Australian version of CLIMPACTS called OzClim (CSIRO, 1996b). This is part of a broad-based climate impacts "tool kit" that has been adopted as a goal of the CSIRO Climate and Atmosphere Sector. A comprehensive model for assessing the effect of climate change on pests and diseases also has been applied in Australia (Sutherst, 1995; Sutherst et al., 1996) and could be part of an impacts tool kit.

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