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
- The chain of effects, from changes in atmospheric composition and climate
to changes in biophysical systems to socioeconomic consequences (the "vertical"
- The interactions between systems, sectors, and activities (the "horizontal"
- The context of other trends and changes in society, such as population,
technology, land-use, and economics (the "time" dimension).
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 1°C 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.
(continues on next page...)