Greenhouse: Planning for Climate Change

Greenhouse: Planning for Climate Change

It is important for the reader to understand clearly the objectives of these papers. They are not an attempt to provide accurate predictions of what is going to happen in Australia over the next few decades. Rather they represent sensitivity studies, designed to illustrate to what extent we as a nation are dependent on the climate and likely to be affected by climatic change, and attempts to develop the techniques for such sensitivity analyses. For this, the climate scenario (reproduced in the Appendix to this volume), was a key.

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      The last decade has seen an enormous growth in our knowledge of the trace-gas composition of the global atmosphere. Now, after extensive national and international research on this topic, it is becoming clear that the atmosphere demonstrates a chemical weather and climate as complicated as the physical weather and climate. We now understand that the chemical climate is changing, particularly with respect to those gases which we call greenhouse gases.

      This paper highlights some of the evidence that greenhouse gases have increased in concentration and are likely to continue to do so in the coming decades. This evidence forms the basis upon which estimates of the climatic response to these changes can be made.

      The key greenhouse gas species which are identified are carbon dioxide (CO2), methane (CH4), nitrous oxide (N2O), tropospheric ozone (O3) and several halocarbon species. Since preindustrial times, CO2, CH4 and N2O concentrations have risen by 23, 110 and about 8% respectively. Current rates of increase are 0.4, 1.0 and approximately 0.3% y−1 with estimates of increases of 45–115, 200–500 and 25–60%, respectively, above preindustrial levels over the next 50 years.

      The evidence that tropospheric ozone is increasing is not convincing even though there are reasons to believe that it may increase by up to 50% in the future. The key chlorofluorocarbon gases CCl3F (CFC-11) and CCl2F2 (CFC-12) are both increasing at rates of about 5% y−1 having been none existant in the atmosphere prior to the 1930s. They are expected to increase by about 300% in the next 50 years. Several other such man-made gases are also expected to make a contribution on these time-scales.

    2. Page 22

      This review for non-specialists argues that a numerical modelling approach is the only reliable way to obtain estimates of the effect on climate of increasing levels of trace gases in the atmosphere. Three types of numerical model have been used for this purpose; in increasing order of complexity they are: energy balance models, radiative-convective models and general circulation models (GCMs). But GCMs are the best means of quantitatively synthesising the wide range of processes at work controlling climate. An outline of some of the difficulties associated with GCMs is followed by extracts from some recent results, including one which shows limitations in the ability of modern GCMs to simulate the present southern hemisphere climate.

      Confidence in GCM estimates of future climate change will depend on:

      • Their ability to simulate current climate.

      • The similarity between results from different models.

      • The emergence of a climate change signal from the real atmosphere which conforms to model predictions.

    3. Page 35

      Basic physical considerations suggest that an increase in the concentration of infrared absorbing gases in the atmosphere will lead to warming at the Earth’s surface and in the lower atmosphere, and cooling in the upper atmosphere. Complex feed-back processes, especially those involving increased water vapour and cloudiness in the atmosphere, make precise estimation of the degree of warming difficult. Also, the timing will be affected by the rate of increase of the concentration of the gases, which depends in part on future human actions. The oceans will also play a major role in delaying the effects, and in altering them due to transient phenomena and changes in ocean circulation. Even the best available climate models do not convincingly model all these effects, although progress is being made.

      Existing climate models do provide us with a range of estimates of zonally averaged climatic changes. Various methods have been used to relate these to likely regional climate changes using our knowledge of past climatic variations. However, the resulting picture is still very generalised and imprecise, especially when it comes to local changes in rainfall, cloudiness, tropical cyclone occurrence, frequency of extreme events and other phenomena which are of local economic importance.

      The climate scenario which was issued to speakers at this conference is not, therefore, a confident prediction, nor is it very detailed. Results based on this scenario should thus be viewed not as predictions, but as sensitivity studies, to give us an idea as to how seriously various sectors or activities would be affected by changes which could well occur over the next several decades.

      In order to obtain improved and more detailed estimates of probable climate change, existing climate models need improved representation of variable cloudiness, interactive and dynamic oceans, and much greater spatial resolution. Such improvements are planned in several laboratories around the world. However, for Australian purposes we need a model which focusses on the Australian region. We are planning to develop such a capability in CSIRO and the Bureau of Meteorology, and look forward to cooperation with those groups which have particular needs for output from the model.

    4. Page 52

      Radiosonde temperature data from 31 stations in the southern hemisphere for the period 1950–85 have been used to investigate recent temperature trends in the southern hemisphere troposphere and lower stratosphere.

      First, the temperature trends in the lower troposphere are described. Most stations show a warming trend in the lower troposphere over the period 1950–85 of 0.1 to 0.5°C per decade. This warming trend is significant at 11 stations. By examining the first and last twenty-year periods separately, the warming trend is found to be larger in the last twenty-year period, 1966–85. In this later period, all stations show a warming trend, which is typically in the range 0.2 to 0.8°C per decade.

      Second, the temperature trends in the lower stratosphere are compared with those in the lower troposphere at 19 stations. Radiosonde temperature data for the lower stratosphere are available from 1964 only. For the period 1964–85, there is a cooling trend in the lower stratosphere and a warming trend in the troposphere at most stations. Experiments with atmospheric general circulation models indicate that increased concentrations of CO2 in the atmosphere will lead to reduced temperatures in the lower stratosphere as well as increased temperatures in the troposphere. An index designed to identify this signal has been computed from the radiosonde temperature data. This index has a trend of the same sign at all stations and the trend is significant at most of the stations.

      Both the warming trend in the lower troposphere and the cooling trend in the lower stratosphere are consistent with the impact of increasing concentrations of greenhouse gases in the atmosphere. However, there are other possible mechanisms, such as increasing sea surface temperatures or decreasing ozone amounts, which also would be consistent with the observations. The data are available for a relatively short period so conclusions about long term trends may not be reliable.

    5. Page 60

      It has been predicted that sea level will rise as the result of global warming produced by the greenhouse effect, and some analyses of tide gauge records have indicated that a global sea-level rise is already in progress. However, the distribution of reliable tide gauges is not yet representative of the world’s coastline, and it will be some time before the results from improved global networks of tide gauges and geodetic surveys are available. Models of the potential impacts of a sea-level rise on cliffs and shore platforms, beaches, lagoons and estuaries, marshlands, coral reefs and shore zonations of marine organisms are considered, and suggestions made for surveys and monitoring of physiographic features that could indicate a sea-level rise.

    6. Page 74

      The current average rate of rise of global sea level over the last century amounts to about 1 mm y-1. The rise in sea level can be caused by many factors including increasing ocean temperature and an increase in water mass balance. In terms of mass balance the 1 mm y-1 over the ocean area of 361×106 km2 represents a water volume increase of 361 km3 y-1.

      The Antarctic ice sheet is considered to be close to a steady state in mass balance with a net accumulation of about 2×103 km3 y-1, over the area of of about 13.6×106 km2, being approximately balanced by ice flow and calving of a similar amount. The uncertainties in the balance estimates exceed 20% which in absolute terms is larger than the volume of water involved in the current rate of sea-level rise.

      The major effects of global warming in the Antarctic which can affect future sea-level changes are possible increases in precipitation, which have a negative impact, and basal melt of the ice shelves, which could ultimately give rise to faster flow of the grounded ice, which would give a positive impact to sea-level rise.

      Numerical modelling of ice-sheet flow indicates that increased sliding speeds up to an order of magnitude above present rates could then lead to a reduction in the volume of grounded ice. The effect on sea level could reach up to 0.3 m in the first century and about 1 m by 500 years. The new steady state would be reached only after some 5 000 years with a total increase to sea level of about 4.5 m. These changes, although serious and possibly irreversible are sufficiently slow to be monitored and the impacts managed.

    7. Page 83

      Plant photosynthesis has transformed the pre-biotic anaerobic atmosphere that was rich in CO2 to a modern atmosphere, fit for advanced life, containing 21% O2 and only a trace concentration of CO2. Modern vegetation also plays a significant part in determining climate by affecting the partitioning of incoming solar energy over land. This partitioning may change as a result of CO2 effects on vegetation. In one way or another vegetation contributes to and/or is affected by the other major changing components of the global atmosphere - O3, CH4, CFCs, N2O.

      Current best estimates of the scale of net deforestation of the world indicate that it is releasing about a quarter as much CO2 to atmosphere as fossil fuel burning is. However, the increasing CO2 concentration in the atmosphere is probably increasing the growth of vegetation. It is estimated that the net annual storage of extra carbon in the form of more standing biomass and soil organic matter than hitherto, may approximately equal the carbon released by net deforestation. Quantitative appraisal of the global carbon cycle reveals that to attempt to permanently remove the fossil fuel-derived CO2 from the atmosphere by massive re-afforestation or by storing felled timber is unrealistic. Refraining from continued net deforestation would, however, produce a probably detectable slowdown in the rate of build-up of atmospheric CO2.

    1. Page 93

      Australia’s open coastline is dominated by Holocene sedimentary deposits composed of sand (16 000 km) and mud (6500 km). In addition, hundreds of deltas, estuaries, coastal lagoons and bays contain more ‘protected’ shorelines of equal magnitude. The impact of a sea-level rise on all shorelines will depend on their cross-shore gradient which would determine the pro rata extent of permanent sea-level inundation and shoreline retreat. The low gradient (1:1000 to 1:10 000) inter and supra tidal flats, chenier and beach ridge plains particularly in northern Australia would be most affected by a rise with a 1m increase producing shoreline retreat of up to 1000’s m. Furthermore, the effects of higher frequency oscillations in water level associated with waves, tides, storm surges, shelf waves and flooding will result in periodic inundations of up to several meters above sea-level. In northern Australia periodic inundation is associated both with the meso- to macro-tidal ranges and with the episodic occurrence of storm surges and coastal river flooding. In southern Australia waves play a greater role in periodic inundation, in particular wave uprush and set-up during high-wave events. These are compounded across the Southern Ocean coastlines by the regular passage of higher amplitude shelf waves and occasional storm surges. On the higher wave-energy sections of the southern Australian coast and parts of the northern coast beaches have relatively steep gradients (1:10 to 1:50) and are usually backed by foredunes 5 to 20 m high. While the foredunes would prevent much overwashing and landward inundation they could experience massive scarping and erosion which could accelerate the present phase of coastal dune instability in southern Australia.

    2. Page 105

      A possible rise in sea levels of 0.2–1.4m over the next 40 years plus associated changes in temperatures, river discharges, water tables, cyclone/storm activity inter alia would have a range of impacts on social and natural functions of the Australian coastal zone. The judgement is made that the changes foreseen are well within society’s capacity to adapt; this does not mean that society should not address its limited planning capacities to the issue and several recommendations to this end are made. Also to this end, the Australian Resources Information System (ARIS) is used to produce a map of the Australian coast classified with respect to priority for undertaking climate/sea-level impact assessments. The primary basis for prioritisation is population proximate to and population resident within each coastal sector; this initial rating is adjusted for foreseen impact with respect to increased flooding, erosion, storminess and salt water intrusion.

    3. Page 121

      Sea level on the New South Wales (NSW) coast of Australia has risen some 0.1m since the mid 1920’s. Evidence suggests that prior to this, in the late 1890’s to early 1900’s, it rose to a peak in about 1911 before falling to the record low in the period 1925 to 1930. Whilst there are now some 100 years of reliable data for the Sydney gauge, and these data suggest an overall sea-level rise trend, caution must be exercised if this information is to be applied to coastal process analysis as the short-term fluctuations in the record, the ‘noise’, are of the same order as the trend.

      Detection and quantification of long-term trends in coastline movement (engineering time scale), are generally based on historical survey records and/or aerial photography. Whilst in some areas on the NSW coast accurate beach and back-beach surveys are available over a period of more than 100 years, in general suitable survey data only span some 50 years, from the 1930’s onwards. Vertical aerial photography and the associated technique of photogrammetric analysis were technological developments of the 1940’s era which provide an additional source of beach recession data for most regions of the NSW coast. Thus the two main sources of data on coastal response provide an estimate of coastal behaviour for the past 40 to 50 years - the period during which there has been a recorded sea-level rise.

      The detailed coastal process studies at specific sites suggest that much of the coastline is presently experiencing a recessional trend which has been present for at least the past 40 to 50 years. At most locations studied the long-term averaged recession rates vary from less than 0.2 m y−1 (lower detection limit) to 1.5 m y−1. Most beaches studied fall into the 0.2 m y−1 end of the range.

      Although it is generally recognized that sea-level rise results in coastal recession, to date the models used to describe the mechanism have been somewhat simplistic. Quantification of the process including determination of the response time is therefore difficult. An insight into the relationship may be gained by examination of the impact of the last post glacial sea-level rise (17 000 y B.P. to 6500 y B.P.). It resulted in a time averaged rate of rise of some 12 mm y−1 as compared to the present 1.5 mm y−1.The coastal change associated with the Holocene sea level rise continued for some 5000 years after sea level stabilized and resulted in a major change in shoreline location. When the observed sea-level rise over the past 50 years is entered into the basic response models, the recession rates obtained are of a similar order of magnitude to those given by the site specific process studies (0.2 m y−1). Therefore, whilst significant reservations must be held as to the validity of conclusions based on such meagre evidence, it would appear that there may be a tentative if not tantalizing link between the recent sea-level rise and the present coast-wide recessional trend.

    4. Page 135

      The greenhouse scenario assumes that sea level will rise worldwide at uniform rates because of near-polar ice melting or because of thermal expansion of ocean waters. This view ignores the natural variability of existing sea-level behaviour that occurs globally over time. It also ignores the fact that some of this variability is related to changes in climatic parameters such as precipitation, barometric pressure and temperature that will be influenced by the greenhouse effect.

      This paper presents existing evidence on sea-level variability across the globe and links it to changes in atmospheric pressure, air temperature and precipitation for the period 1933–1980. Rapid fluctuations in rates of sea-level change occur over distances as little as 200 km. Additionally, sea-level directly responds to changes in climatic variables near areas of greatest seasonal climatic change, namely the coastlines affected by the Asian monsoon and beneath the path of the polar jet stream in the northern hemisphere. Aseasonal effects are greatest along coastlines bordering the Aleutian and Icelandic lows. The current postulated worldwide rise in sea-level of 1.0–1.5 mm y−1 may be occurring concomitantly with increasing climatic trends in temperature, precipitation, surface pressure and intensity of pressure cells.

      These results will have a significant impact within the greenhouse scenario. An accelerated worldwide rise in sea-level will be difficult to detect because of the inherent variability that exists over time and space. Seasonal and inter-annual variability in tropical regions can exceed 40 cm and already poses a natural hazard that will only be exacerbated by the effects of a global rise due to greenhouse warming in these locations. In some temperate locations, rates of sea-level rise already exceed rates proposed within the scenario, while in parts of Scandinavia and northwestern North America negative rates will locally reduce the impact. Because of the linkages in behaviour between sea-level and climatic variables, negative and positive feedback will be superimposed at regional levels upon any global sea-level rise induced by the greenhouse effect. This will add a degree of uncertainty to sea-level predictions at many locations.

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      The well defined pattern of vegetation zonation on most saltmarshes reflects the relative tolerance of various plant species to the extent, frequency and duration of inundation by seawater. Small differences in elevation are accompanied by marked floristic changes.

      Rather than attempting to measure sea-level change directly, it is proposed that ecological indicators, such as changes in saltmarsh vegetation, may supply useful additional data and perhaps alternative methods of detecting changes in sea level.

      Initial investigations of the marsh islands at Corner Inlet have found landward migration of plant species, accompanied by the erosion of island shorelines. It is suggested that this has occurred as a result of submergence due to tectonic subsidence of the Corner Inlet Basin. An examination of the associated changes in saltmarsh vegetation provides a useful model for the response of other southeastern Australian saltmarshes to the proposed rise in sea level as a result of the greenhouse effect, and may allow them to act as early indicators of such a rise.

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      The greenhouse effect will impact on coastal and marine structures and developments with a threefold attack. The predicted physical changes which engineers must now consider in designing such structures, and developments, are (i) a rise in mean sea level, (ii) an expected increase infrequency of and areas affected by tropical cyclones, and (iii) an increase in intensity of cyclones.

      If current scenarios concerning changes in cyclone frequency and intensity do occur, coastal and marine structures will be subjected to cyclonic storm surges and wave attacks at levels considerably higher than current designs anticipate. Inundation of low-lying coastal developments and of maritime (port) infrastructure can be expected.

      As the design life of important structures and some of the major coastal developments now under way in tourism and offshore projects will be at least 50 years and in some cases more than 100 years, planning to cope with these changes must be incorporated in designs now. Some valuable real estate areas will require special protection.

      The greenhouse effect if it follows currently predicted patterns will increase the vulnerability of all coastal structures and developments but this increased vulnerability could become critical if such projects (i) are in current cyclone areas but have not been properly designed for cyclonic storm surges or (ii) are in those areas which will become affected by cyclones because of the predicted climatic changes.

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      Central to the task of planning appropriate management responses to a greenhouse-induced rise in sea level, is an understanding of the nature and extent of physical changes that are likely to occur in different coastal settings. In southeastern Australia such a record of coastal change is provided by marine sedimentary deposits that were laid down during the Postglacial Marine Transgression (PMT) between c.17000 and 6500 years ago. This event, which accompanied melting of the ice sheets, caused sea levels to rise about 120 m and to flood the continental shelves of the world. The average rate of relative sea-level rise at this time (12–15 mm y−1) was similar to that predicted for the next 50 years, and it is therefore appropriate to use the past as a key to assess future coastal change. It has been possible to document the rate and direction of shoreline change during the PMT, and over the past 6500 years of relative sea-level Stillstand, in a number of different shelf, coastal and estuarine settings in southeastern Australia. These studies point to a set of response patterns in shoreline position, in geometry of depositional units, in sediment composition and in ecological characteristics. These response patterns vary in space and time. The complex behaviour of response patterns of shorelines to changing environmental conditions in the past highlights the difficulties in predicting coastal environment variation in the future. Changes can take place as a result of shifts in boundary conditions (eg sea-level rise, increased storminess), or as a consequence of internal adjustments within any given sediment budget system. We advocate caution in predicting the impact of the greenhouse effect on the coastal zone unless there exists a clear understanding of both the theoretical and empirical nature of shoreline change in different environmental contexts.

    8. Page 189

      Within the given scenario of a sea-level rise of 0.2 to 1.4 m by the mid twenty-first century, the response of the Great Barrier Reef in the short term is likely to be beneficial. Large areas of currently depauperate reef flat produced by a long period at modern sea level (ca 6000 yrs) will be reoccupied by corals and become aesthetically more pleasing, as can be illustrated by a number of modern analogues. Coral cays, although generally less than 3 m above High Water may also show minimal impact as inundation produces more efficient transport of sediment to the cay site. However, both geological time-scale results produced from dated reef cores and modern metabolic studies suggest that over longer time scales reefs as a whole have the potential for a maximum vertical accretion rate not exceeding 8 mm y−1 or approximately half that predicted by the greenhouse effect, with many parts of the reef falling well below this figure. Thus the long term effect will be a progressive drowning of reefs and loss of coral cays. Climatic changes such as increased rainfall, greater cloudiness and higher temperatures have the ability to affect reef growth but within the ranges predicted are unlikely to pass thresholds which will have more than a trivial short term effect.

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      A number of tropical cyclone storm surge climatologies for three Australian ports, Darwin, Mackay and Port Hedland, are presented. In the first instance, continuance of the present climatological regime is assumed and the difficulties of developing an extreme event climatology from the conventional meteorological data base are discussed. With distributions of the frequency, intensity and velocity of landfalling tropical cyclones an open coast surge model is used in conjunction with a simple Monte Carlo technique to generate the required surge climatologies.

      A second set of climatologies is derived after specifying possible responses of the tropical cyclone climatology to a sea-surface temperature (SST) warming of the order of 1.0°C in the oceans surrounding northern Australia accompanied by a sea-level rise of 1 m. It is shown that a 1 m sea-level rise increases the possibility of major surges by between a factor of 4 at Darwin to a factor of 13 at Port Hedland. This change in sea level offers the possibility of decreasing the return periods of extreme surges from tens of thousands of years to around a thousand years. If the sea-level rises are accompanied by more frequent and more intense cyclones these extreme events could possibly have return periods of only hundreds of years. These results are crucially dependent on the method used to compute the return periods of extreme events under present climatic conditions and the assumptions made on likely changes to the regional climate. It is noted that there is a high degree of uncertainty in specifying likely changes to the climate in the Australian region given a global warming trend.

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      The population sizes, and related commercial catches, of penaeid prawns in northern Australia are dependent on a large number of environmental factors which interact with the prawns’ relatively complex life history. Physical factors, including currents, tides, rainfall and runoff, affect larval dispersal from the offshore spawning grounds to the nursery grounds. They also affect the immigration and emigration of postlarvae and juveniles to and from the nursery grounds. Biotic factors such as mangrove extent and seagrass extent, species composition and density will affect the carrying capacity of these nursery grounds, the population size of subsequent stages and hence the ultimate catches. If the greenhouse effect leads to higher sea levels, higher rainfall and increased cyclone activity we would expect an increase in banana prawn (Penaeus merguiensis) catches and a decrease in tiger prawn (P. esculentus and P. semisulcatus) catches largely due to alterations in nursery grounds. The magnitude of these changes is hard to predict given the uncertainty of both the localised changes due to the greenhouse effect and their direct relationship to prawn populations.

    1. Page 231

      An attempt is made to infer changes to the rate of movement to rivers and reservoirs of sediment eroded from hillslopes and tributary streams under the climatic conditions that might prevail on a warmer Earth. Numerical simulations of future conditions are not possible because an adequate model of the sediment delivery system is not available. Inferences are therefore based upon analogues from the past as well as a simple manipulation of hillslope erosion rates. There is a slightly more direct relationship between climate and wind erosion thereby allowing firmer conclusions about the future.

    2. Page 238

      In Australia, groundwater supplies are essential for some cities, many country towns and mine sites, and large areas of grazing leases. Moreover, shallow water-tables are a major problem contributing to salinity of farmlands. The impact of climate change on groundwater systems has previously received only passing mention in the scientific literature.

      Aquifer recharge from direct infiltration of rainfall can be an important process when there is a significant period in which rainfall exceeds evaporation. A model of water drainage beyond the root zone of plants was used to show that, with unchanged vegetation, recharge may change by −70% to +230% for rainfall changes of −20% and +20% in a summer-rainfall environment, and by −60% to +35% for similar changes of rainfall in a winter-rainfall area. The greatest fractional changes are in situations of very low recharge rate. The model predicts that a 20% decrease of potential evaporation would increase drainage and recharge by about the same amount, or more under low drainage conditions. These predictions may be compared with analysis of groundwater depths at several locations over many years with varying annual rainfall. The latter data suggest recharge changes of ±35% and ± 50% for ± 20% changes of rainfall in a higher rainfall area, and by ±25% and ± 40% in a nearby lower rainfall area.

      The distribution of hydraulic head in a groundwater system depends on the climate-driven recharge rate. Using a simple model of the Gnangara Mound, a major aquifer close to Perth, with ± 30% changes of recharge, it is concluded that changes of water-table level of about ±10 m would result. Such an increase of head is not possible in parts of this aquifer, because the water table is generally shallower than 10 m. As the water table approached the ground surface, swamps would develop in low lying areas and net recharge would fall because of increased evapotranspiration. A decrease of water table level by 10 m would drain lakes and swamps and add to the costs of pumping water from the aquifer.

      Lower water-table levels from decreased precipitation would ultimately result in a reduction of areas of saline land. Higher precipitation and recharge would increase saline areas and areas of shallow water table, but the extent of these increases is not readily estimated.

      The discharge of saline aquifers into streams and rivers will tend to increase as a result of increased recharge. When increased precipitation also affects the level of water in the stream or river, however, there may be a period in which saline discharges firstly fall. Although the quality of water in an aquifer may ultimately improve under higher recharge conditions, the time-scale of this process can be very large.

    3. Page 252

      In southern and south-eastern Victoria, Australia, salinity is mainly a groundwater problem caused by the filling of aquifers as a result of land-use changes introduced with European settlement. These changes, the principal ones being the removal of the forest cover and the introduction of irrigation schemes, have tilted the delicately balanced hydrological equilibrium towards steadily increasing salinity.

      The impact of the greenhouse effect is largely climatic in nature. However, the influence of climatic variation is not immediately apparent, because rising water tables and salinity already occur in widely ranging existing climatic regimes. Indeed, it is clear, when considering the distribution and severity of salinity throughout Australia that neither rainfall nor temperature are particularly critical factors. The exception is the effect that extreme events have, particularly very high rainfall or flood, when recharge causes a significant increase in aquifer pressure and a consequent rapid rise in water-tables. Droughts though, have virtually no impact upon most saline groundwater systems and least effect on regional aquifers. The distribution of salinity is instead best related to the distribution of groundwater discharge zones, which are in turn determined by geomorphic and hydrogeological factors. The future influence of the green-house effect on water tables is seen, therefore, in terms of the extent and incidence of these major recharge events.

      The greenhouse changes will simply result in a modification of already existing strongly developed hydrogeologic trends, of which salinity is a major consequence. While groundwater systems, and hence salinity of soils, are unlikely to be greatly affected by the impact of greenhouse-induced climatic changes, the effects could be significant on surface water bodies, especially streams. This may affect salinity strategies involving long-term planning for salt disposal schemes utilizing the River Murray system. Whatever the case, the technical and administrative infrastructures for salinity monitoring, salinity control and long-term strategy development are already well established.

    4. Page 261

      It has been postulated that there is an ongoing build up of trace gases in the atmosphere which will lead to changes in the world climate: this is the greenhouse effect. The predicted impacts to Australia which will occur within the next few decades, include a 2–4°C rise in annual temperatures and an increase in summer rainfall of up to 50%. Such changes will have an important impact on flooding in the areas so affected. It is difficult to predict the magnitude of these changes because it is not easy to assess how the various associated factors will be modified. However, the likely changes can be estimated by considering a number of representative situations. This analysis addresses the two distinct aspects of the problem. First, what will be the impact on structures already constructed? How would their level of performance be reduced? Second, what changes will need to be made to maintain performance standards for new works? In general, it can be said that frequent events will be proportionally increased more than infrequent events.

    5. Page 273

      The climatic changes induced by greenhouse gases that are expected to occur within the next 50 to 100 years will affect the magnitude and seasonal distribution of temperature and precipitation. Such changes must be expected to alter the existing streamflow regime and thus will have consequences on aspects of engineering hydrology such as the planning and construction of major water resource systems and the timing and frequency of flood events. The effects will also be felt in agriculture, for example soil erosion and the availability of soil moisture for crop production.

      This paper investigates the impact of these expected climatic changes on some aspects of catchment hydrology and reservoir reliability. Two catchments are selected that are subject to substantially different climatic conditions. One, Myponga Weir in South Australia, is dependent upon winter dominated rainfalls, and the other, Moogerah Dam in Queensland, derives high summer and early autumn rainfalls from the Australian monsoon season. Stochastic data generation techniques are used to derive 1000 year daily-rainfall sequences corresponding to the range of climatic changes expected over the next 50 year period. This rainfall data, and expected changes in evaporation rates, are input into a conceptual, physically-based rainfall-runoff model to determine the influence of climatic variation on streamflow and soil moisture characteristics. The streamflow data is also used to determine the impact of climatic variation on the yield-reliability relationships of the two reservoirs. The study indicates a considerable amplification of the effect of climatic change on soil moisture availability, flow duration and flood frequency curves, and reservoir reliability.

    6. Page 296

      The south west of Western Australia is the region where most Western Australians live and enjoy a Mediterranean climate. The warming of the earth’s lower atmosphere due to the greenhouse effect is expected to move the sub-tropical high pressure systems southwards and cause some blocking of the rain bearing fronts which bring winter rains to the region from the Westerlies.

      A decline in rainfall is expected which researchers are predicting could be as much as 20% by the year 2040. Using a simple statistical relation between historical rainfall and streamflow it is estimated that the streamflow in the region could decline some 45% as a result of such a rainfall decrease. Groundwater recharge is also expected to be severely reduced.

      Water supplies in the region are based on a combination of surface resources and groundwater resources. The fresh water resources are under strong pressure from regional development, particularly in the vicinity of metropolitan Perth.

      Simulation models indicate that the result of the projected hydroclimatic changes could be that the yield of the sources for Perth’s public water supply will decline by some 35% to 45% over a 50 year period. A result of this change would be to increase the Present Value of the capital and operating costs of future source development works by as much as threefold. Considerable pressure will be placed on the region’s limited water resources including important wetlands of the coastal plain. A regional salinity problem which results from agricultural clearing, will require greater attention because of declining fresh water resources, and interaction of the climate changes with salinity trends and management.

      The Water Authority of Western Australia is considering strategies for progressively adapting to the regional effects of climate change. Public decisions in problems of this kind are generally very slow in developing, an issue which needs special attention. In terms of research, the most urgent need is for support to general policy decisions by improvements in confidence of basic climatic forecasts.

    7. Page 312

      Water resource planning studies conducted by the River Murray Commission use computer models to examine how the River Murray system would have behaved if the current storages and the current irrigation development had existed for the last 94 years. The use of these studies makes the assumption that the last 94 years of flow and rainfall data are representative of current conditions. Recent studies have revealed that in much of the Murray-Darling catchment, the average rainfall in the last 30 years was higher than in the previous 30 years. There is also evidence to suggest that this increase in rainfall corresponds to an increase in temperature in the southern hemisphere. An examination of the natural inflows to the River Murray reveals a similar increase in streamflows. This is borne out in the planning studies which show that all the major periods of restriction occur before 1950.

      By making the assumption that the change in streamflow over the last 60 years is typical of the change that might result from future greenhouse effect warming, it is possible to make an estimate of the impact of the greenhouse effect on the water resources of the River Murray. These studies reveal an improvement in the security of supply to water users on the Murray and a reduction in river salinity as a result of increased dilution flows.

    8. Page 324

      Over 90% of irrigation development in the state of Victoria (Australia) occurs off river systems north of the Great Dividing Range. One of the two major water supply systems in northern Victoria, the Goulburn System which is based on the regulation of the Goulburn, Campaspe and Loddon Rivers, has been analysed using a computer simulation model to assist in assessing the potential impact of climatic change on existing irrigation development.

      The postulated changes in winter/spring rainfall (10% reduction) and evaporation (5–10% increase, depending on season) adopted as the greenhouse scenario were translated into runoff reductions using rainfall-runoff relationships reported in the relevant literature. The adopted relationship was confirmed by analysis of rainfall and runoff data for the Goulburn River catchment.

      The system simulation model which uses 91 years of historical streamflow, rainfall and evaporation data was first run to establish a “benchmark” of system performance and security of supply under existing climatic and demand conditions. A series of model runs was then undertaken to study the effect of climatic change on system performance. The major conclusion drawn from the studies is that existing irrigation storages would not be able to satisfactorily support the current level of irrigation development in the future should the forecast climatic change eventuate.

      Further studies showed that a 20% reduction in total demand would be required to maintain a long-term distribution of seasonal allocation levels similar to current conditions.

      With more efficient use of irrigation water and the likelihood of a shift away from dairying to other less water intensive farming enterprises, it is expected that the reduction in total area under irrigation in northern Victoria would not be as high as 20%. However, under the adopted climatic change scenario and without any further storage development, it appears inevitable that adjustments of considerable magnitude would be necessary.

    9. Page 339

      Rainfall-runoff and water supply system simulation modelling of the Severn Valley demonstrates the sensitivity of streams and water supply systems in inland New South Wales to greenhouse climate changes. The effects on flows and system performance were found to be two to three times greater than changes to rainfall or to evapotranspiration.

      The study compared well with those contained in a World Meteorological Organisation report. The combined results indicate a relationship between present average rainfall level and sensitivity to greenhouse changes with more arid areas showing greater reaction.

      Water planners must consider the impact greenhouse changes could have on water supplies when making long term development decisions. The lack of reliable regional predictions of change combined with the uncertainties inherent in rainfall-runoff modelling make the task difficult. The provision of the best advice on both likely climate movement probabilities and regional hydrologic sensitivities will be essential to planning for a greenhouse affected world.

    10. Page 350

      The possible effects of climatic change scenarios on the largest water supply and sewerage authority in Australia were examined. Particular emphasis was placed on the headworks system.

      The changes in the demand for water were assessed on the basis of these scenarios and it was shown that the headworks augmentation program would not be significantly affected. However, increases in probable maximum floods would necessitate expansion of spillway capacity at considerable expense.

      A brief discussion with appropriate costs was presented, on the possible consequences on the water conveyance system, the sewerage conveyance system, the urban drainage system and sewage treatment processes.

      It was concluded that the climatic change scenarios could have important implication for services provided by urban water authorities.

    1. Page 361

      In this paper climatic changes including rises in sea level are discussed within the framework of the biological context of nature conservation in Australia and the role of disturbance in maintaining diversity within natural ecosystems.

      Within ecosystems a changing climate might be expected to initiate changes in the biota analogous to the responses to past warmer and wetter periods. However, this is no longer possible because the natural environment is now fragmented by human settlement. Despite these barriers to range changes, arrays of relatively large reserves across climatic transitions are likely to be well situated to retain much biotic diversity. Rises of sea level, associated with changed storminess, will lead to the reduction in size of islands, particularly low sandy ones. The combined result reduce the habitat for many wading birds, those utilizing salt marshes and trans-equatorial migrants.

      In regions of increased rainfall, water birds will be favoured by the more extensive and reliable wetlands. However, where rainfall is reduced, as is suggested for southwestern Australia, water birds are likely to suffer from reduced habitat as the wetlands contract.

      The combined effects of climatic change are likely to have serious implications for nature conservation management, especially with respect to retaining species, in the face of management of fire hazards, predators, introduced species, competitors and disease such as Phytophthora.

      The range of possible actions is discussed and it is suggested that decision procedures should be established so that rational decisions can be made in the face of uncertainty.

    2. Page 375

      In the long term, the effects of climatic change on wildlife in Western Australia are going to be similar to those that have occurred previously with climatic changes. There will be shifts in the bioclimatic zones and zoogeographical barriers with changes in vegetation communities and corresponding changes in the distribution and abundance of animal species. The major difference from previous periods of climate change is that the rapidity of the change in climate due to the greenhouse effect will not allow time for evolutionary adaptation of species, or even for movement of species into new environments. The redistribution of species, especially the less vagile ones, will be hindered in the more agriculturally developed parts of Australia because of their isolation in remnants of natural ecosystems. Thus some species may become locally or even regionally extinct quite rapidly.

      Changes in agricultural activities, including the abandoning of current agricultural land and the development of new agricultural land will also have an impact on wildlife by causing alterations to habitats additional to those caused by climate change.

      As winter rainfall areas become drier, the distribution of Bassian species will contract to the wetter areas of the southwest of Western Australia, and that of Bassianl Eyrean species spread into the southwest. Specific examples are given for amphibian, repitilian and avian species. In woodland, loss of trees will affect many of the hole-nesting bird species. Initially, these species will benefit from an increase in hollows but in time their numbers will decline. The most immediate impact in the southwest will be on wetland species. There will be large reductions in ducks and other water birds due to loss of coastal wetlands. Many of the trans-equatorial migratory waders would also be forced to find other winter habitats.

    3. Page 387

      A preliminary scenario for greenhouse-induced climate change implies a potential geographical rearrangement of the climates currently experienced by the Australian flora and fauna. BIOCLIM, a bioclimate analysis and prediction system, was used to simulate the geographical implications of climate change for alpine and temperate rainforest vegetation and a rare and a common mammal species.

      The present alpine vegetation is restricted to disjunct mountain tops and high plateaux in southeastern Australia. According to the scenario, the alpine climate will retreat to a very small number of isolated mountain peaks. A mass extinction of the present alpine species could be expected to accompany such a predicted dramatic reduction in area.

      Temperate rainforest is presently a conspicuous feature of western and northeastern Tasmania and occurs as isolated patches in south central Victoria. The postulated change would make the climate of most of Tasmania marginal for rainforest, the most favourable climate moving to the mountains of northeastern Victoria and southeastern New South Wales, where temperate rainforest is presently absent.

      Potorous longipes, the Long-footed Potoroo, has a highly-restricted distribution in far eastern Victoria, with one record from New South Wales. After the postulated climate change, the only area predicted to have a suitable climate is on the western border of the Australian Capital Territory, over 200 km away from the species’ present location. The continued survival of the species must be considered doubful.

      Macropus antilopinus, the Antilopine Wallaroo, currently has a wide distribution across northern Australia. The climate scenario implies a restriction of the suitable climate to two small areas in Queensland, while the climate of the vast majority of its present range is predicted to become unsuitable.

      Climate change may imply significant distribution changes, with severe reductions in at least some cases. This makes management of the native flora and fauna using the present conservation reserve system a very much more complex task. The actual impact of climate change will be very difficult to assess, being dependent on the ability of a species and its predators, competitors and prey, to adapt to the change or to migrate through available corridors to more suitable areas. While active management by man, at least of some of the larger animals, may prove feasible, this is unlikely to be the case with entire ecosystems, with their many thousands of plant and invertebrate animal species.

    4. Page 399

      This paper attempts to forecast the most likely consequences of global climatic change for the ecosystems and land use of arid Australia; the innermost 70% of the continent. Two simplifications are used. The first is that the essential characteristics of ecosystems are determined by the vegetation component; the second is that only two factors of climate are relevant: rainfall and temperature. The direct influence of increasing carbon dioxide (CO2) on arid zone vegetation is as yet unclear and is temporarily discounted.

      To forecast vegetation change in response to climate at continental scales requires an understanding of the relative influence of climate and edaphic factors in determining the existing patterns of distribution, structure and productivity. Rainfall, temperature (T)and the hydrological characteristics of soils interact in determining plant-available moisture (PAM) while, in the short term, soil type alone determines available nutrients (AN). Using existing vegetation and soil maps, the scale-dependent hierarchy of interaction of PAM/AN/T is demonstrated.

      Vegetation change in the arid lands will be influenced primarily by changes in PAM and only secondarily by T; the spatial patterning (distribution) will remain constrained by soil type through its influence on PAM and AN. Forecasts of vegetation cover based on modelling, support the view that the process and rapidity of change will be determined not only by changes in the mean climatic variables, eg. rainfall, but also by the variability associated with that mean. Estimates of the spatial and temporal variability of future rainfall and temperature regimes are essential but not yet available from existing climate models.

      The indirect effects on vegetation and land use of climatic change are predicted to be substantial. These include changes in the wildfire regime (frequency, intensity and extent) and in land use with opportunistic cultivation of the less arid margins.

      The forecast changes in vegetation to 2030 AD will have a marked effect on the pattern and intensity of pastoral landuse. Of the two livestock industries, it appears that wool-growing will be the most seriously and detrimentally affected. The existing boundaries between crop- and range-lands will change, with the potential for an advance or retreat depending upon geographic location.

    5. Page 421

      The daily McArthur Mark 5 Forest Fire Danger Index (FFDI) was calculated for the complete climatological data set for East Sale, Victoria, which covered the period 1945 to 1986. Neither temperature nor rainfall on their own are good predictors for annual summed FFDI. Relative humidity is the climatic parameter with the greatest influence on the FFDI on an annual basis.

      The effect of various climate scenarios on the annual summed daily FFDI at Canberra, East Sale and Hobart was examined. It increases if temperature or wind increases, or if relative humidity or rainfall decreases. However the climate scenarios of interest consist of a combination of these factors in which the temperature, rainfall and wind all increase in summer. There is a tendency for the temperature and wind effects to cancel the rainfall effect though the overall result appears to be an increase in FFDI. Nevertheless, any scenario that assumes that the relative humidity remains unchanged will be unlikely to provide realistic estimates of future bushfire incidence. Estimating the likely changes in relative humidity for any future climate scenario is vital for examination of future bushfire incidence.

    6. Page 428

      Australian snowfields are small with a short and variable season and are very sensitive to changes in climate. The effects of possible greenhouse-induced climate changes are studied by two models based on snow course and climate station data. The models are applied to the ski resorts at Perisher, Hotham and Mt Selwyn and indicate the mean duration of their snow season would fall from about 130,135 and 81 days to about 60,60 and 15 days, respectively, if average winter temperatures rose by 2° C and precipitation fell by 20%. The area suitable for cross-country skiing in New South Wales would fall from about 1400 to 270 km1. If the climate changes occurred in the opposite sense, the snow season would increase to about 180,190 and 140 days, respectively, and the cross country skiing area in New South Wales would rise to 4000 km.

    7. Page 438

      Potential changes in tropical cyclone activity resulting from greenhouse warming-induced climate changes are considered. Interannual variations in cyclone activity are dominated by southern oscillation effects. Because of the uncertainty of predictions of the southern oscillation and of regional climate by present climate models, no meaningful predictions of changes in Australian region tropical cyclone activity are possible. Cyclone activity is likely to increase in the central South Pacific.

    8. Page 456

      Present characteristics of western Victoria’s (Australia) four largest estuaries are described. These are then used as case studies for the likely impact of climate changes on estuarine environments. Likely impacts are analysed under four hierarchical categories:

      • Estuarine morphology.

      • Physico-chemical parameters.

      • Structure of biological communities.

      • Human activities.

      A sea-level peak of +2 m during the Flandrian Transgression has left fossil evidence indicating some of the future changes to be expected.

      Impacts on man-made structures appear to be small for a gradual (40–50 years) elevation in water levels. Barwon Heads and Ocean Grove townships, at the mouth of the Barwon River appear to be most at risk through flooding and bank erosion. Balanced against adverse socio-economic effects are likely benefits due to improved recreational opportunities and an increased potential of estuaries for aquaculture.

    9. Page 473

      Independent evidence from geology, biology and chemistry shows that Australia’s climate has changed in the geologically recent past and strongly suggests that it is likely to continue to change in the future, regardless of any human presence. However, for the past 200 years we have ourselves become more and more active as agents of climatic change, particularly by increasing the concentration of atmospheric CO2. Many workers warn that a world climate warmer and regionally wetter than today could result within the next 50 years. A careful scrutiny of possible former analogues of our likely environmental future is therefore timely.

      During the last 10 000 years Australia’s climate has on occasions been slightly warmer and locally slightly wetter than it is today. In tropical northern Queensland temperatures were highest between about 5000 and 3600 years ago, and precipitation was also apparently higher at this time. In western Victoria, on the other hand, lake levels were very high from about 6500 to 5500 years ago, but were falling between 5000 and 4000 years ago.

      Past environmental analogues are useful in showing rates of change, differential rates of response, and magnitudes of change. Quantitative estimates are now possible using bioclimatic indices derived from modern pollen studies, and salinity estimates obtained from the trace element and stable isotopic composition of fossil ostracod shells from carefully selected sites.

      Antarctic ice-core data show high atmospheric CO2 concentrations during prolonged intervals of warm climate (interglacials) and low CO2 levels during glacial maxima. However, there is no obvious former counterpart to the present very high levels of atmospheric CO2. Future climatic change may be gradual, but could equally be abrupt and rapid.

  3. Page 489
    1. Page 491

      There have been appreciable changes in recorded rainfall in Australia since the late 19th century. These were most marked for summer rainfall in eastern Australia. Water levels at Lake George suggest that there were also changes during the 19th century. At least part of the variation in rainfall appears attributable to El Nino/Southern Oscillation (ENSO) effects. The extent to which the ENSO phenomenon is influenced by greenhouse gases could be a critical factor affecting the future productivity of Australian agroecosystems.

      The major impact of suggested climatic changes could be on the drier frontiers of arable crop ecosystems. Increases in rainfall in subtropical areas could result in expansion of sorghum cultivation into areas where high water holding capacity soils, such as Vertisols, occur. Agroecosystems in predominantly winter rainfall areas are delicately balanced in relation to water. Higher temperatures and evaporation rates may decrease yields but this may be offset to a degree by increases in plant productivity due to higher CC>2..

      Annual variability of wheat yields in Australia is high but there are differences due to both region and crops related to climate. High rainfall variability constrains the application of technology, particularly the use of nitrogen fertilizers. Annual crop-yield variability could increase with further southward extension of summer rainfall and decreased winter rainfall.

      Overall it appears that increased greenhouse gases will have both positive and negative effects of the productivity of agroecosystems. No precise predictions can be made until more information is available, especially on likely changes in the ENSO phenomenon.

    2. Page 506

      Higher atmospheric CO2 concentrations are potentially beneficial to agriculture because they usually stimulate plant growth. The typical magnitude of the "C02fertilizing effect" is a 30–40% increase in yield for a doubling of CO2 concentration to 700 ppmv. Variation in responsiveness depends on plant species and environmental conditions such as temperature and rainfall which may be changing as a result of the greenhouse effect.

      The main mechanisms of the "CO2-fertilizing effect" involve several physiological phenomena, some that are certainly primary (stimulation of photosynthesis, suppression of photorespiration, reduction in stomatal aperture) and others that seem so far to be primary but may turn out not to be (greater leaf area development and branching, reduced stomatal frequency, reduced dark respiration, changes to reproductive development). It is often assumed that the reduction in stomatal conductance at high CO2 concentration will lead to reduced evapo-transpiration from vegetated regions, all else being equal. There are both physiological and boundary-layer meteorological considerations which suggest that this effect might be small though there is some argument about that.

      For annual crops like cereals, a warmer climate will tend to reduce yield owing to the faster attainment of physiological maturity. However, the size of the CO2-fertilizing effect on yield for a currently adapted variety is similar to that of the associated temperature-dependent reduction of yield. So the net effect on cereal yield in a region will depend on the success at introducing slower maturing and CO2-responsive varieties to compensate for faster development in warm conditions, and on whether the climate change involves more or less rainfall in the region.

    3. Page 520

      Australia produced $2.7 billion worth of forest products in 1983–84 but a further $1.3 billion worth, principally softwood, were imported. Because of this ever increasing demand for softwood, there is a move away from utilization of native hardwoods and by 2020 AD, when the atmospheric CO2 concentration is likely to be greater than 450 ppmv, 75% of forest products are projected to come from coniferous plantations. This move towards Pinus radiata is a result of both demand for softwood and lack of in depth investigations of the potential of Australian native species, particularly eucalypts, for plantation forestry.

      Pinus radiata is the major plantation softwood in southern Australia and is presently grown at sites where phosphorus deficiency and repeated episodes of drought are common. Consequently, we are investigating the growth response of pines to elevated CO2 at a range of phosphorus and water levels. When phosphorus was adequate, doubling CO2 concentration more than doubled the rate of photosynthesis and increased the total plant dry weight by about 40%. However, there was no response when phosphorus was deficient. In contrast, there was a slightly higher response under simulated drought conditions.

      A further possible effect of rising CO2 levels is that the climatic range of P. radiata may be altered due to a reduction in water use or an increase in the drought tolerance of the trees. We found that CO 2 enrichment did not affect either of these factors but the water-use efficiency was increased when phosphorus was adequate.

      All families of P. radiata do not respond to CO2 enrichment in the same manner. In a study investigating the response of four families to elevated CO2 at two phosphorus levels, we have identified a considerable variation between the families in their response to CO2 and phosphorus.

      To date our studies have indicated that the projected increase in atmospheric CO2 levels is likely to have a significant influence on the productivity of Australia’s P. radiata plantations. But this will only occur if phosphorus fertilization is adequate. If the rise in CO2 results in climatic change the range of P. radiata may be even further restricted because there will be no concomitant decrease in water use or increase in drought tolerance. There is an urgent need for complimentary studies of the response of Australian native species to elevated CO2 at realistic levels of phosphorus and water to enable more accurate prediction of the productivity and water use of Australian native forests and eucalypt plantations.

    4. Page 534

      Present mean climatic conditions were estimated for 71 major plantation sites, which represent about 90% of the total area of Pinus radiata plantations in Australia. Some simple assumptions were used to estimate annual mean temperature and precipitation at these sites in about 50 years time. The possible effects of changes in coldest month minimum and hottest month maximum temperatures were also discussed.

      A simulation model describing the physiological processes of plantation forest production was used to examine in more detail the likely direct and indirect effects of increasing carbon dioxide and other greenhouse gases. For two sites, one near Canberra, Australian Capital Territory, and the other near Mt Gambier, South Australia, observed and estimated daily meteorological data were used to identify some possible effects of anticipated climatic changes on P. radiata yield.

      More research is needed to monitor and predict the magnitude and pattern of climatic changes. However, if climatic changes of the magnitude assumed here are realized some plantations would enjoy growth increases, whilst productivity could be significantly reduced at other locations. Some tentative suggestions are made about which plantations might be most affected. The climatic changes would not only affect growth rates, but could also increase the risk of serious diseases, such as Diplodea pinea and Dothistroma pini. They might also cause short-term problems with harvest management systems, which currently use yield prediction methods that do not take account of climatic effects.

      As it takes about 40 years to complete the production cycle of P. radiata, the early identification of climate-related problems is important. We conclude that a nationwide program monitoring climate, tree health and growth, should be carried out at selected P. radiata plantations. Some low-cost methods are suggested.

    5. Page 546

      The wide variety of agricultural industries in Queensland, Australia, occur against a background of large spatial and temporal climatic variability. Historical experience and agricultural research have shown that existing climatic variation greatly affects the reliability and economics of production. Areas of cropping and sown pastures have rapidly increased since 1950. The large climatic changes suggested in the scenario presented to this conference (up to 50% increase in spring, summer, autumn rainfall, 20% decrease in winter rainfall, 2°C increase in temperature) would have a great impact on existing production and further development.

      Two methods of evaluation of the influence of such changes were used:

      • Qualitative assessment based on the current climatic constraints to pasture and crop adaptation, and the effect of climatic variability on property management.

      • Quantitative assessment for case study enterprises using simulation models.

      Large changes in cropping and sown pastures could occur with climate change as suitable soils exist in areas presently constrained by low rainfall. The climate scenario would aid development within the existing climate constraints where development has been regarded as too risky. Simulation studies of wheat production showed both benefits (35% yield increase) and risks (trebling of run-off and soil loss).

      Pastoral management problems such as undesirable grass species, shrub invasion, animal nutrition and health, and soil erosion would need careful attention. Technological advances are already available to allow Queensland’s producers to take advantage of changing climatic conditions. As better predictions become available, management changes will be able to be anticipated.

    6. Page 564

      Greenhouse gas climate changes will particularly influence plant development and growth in temperate areas of Australia and New Zealand. Temperature influences development depending on the number of days when temperature exceeds a certain value, the frequency of low temperatures and frost. Precipitation impacts on growth through soil water balance. A temperature increase of 1°C could open a large area of land at higher elevations to pastoralism and allow the introduction of many warm temperate crops south of 40°’S. In oceanic climates the length of the frost-free season increases by 20–30 days. A 2°C temperature warming extends the range of citrus and subtropical crops to 40°S. Less winter chilling means warm temperate crops will yield poorly north of 38°S, bringing the ideal latitude range 4° poleward. The length of the frost-free season increases by 20 days in continental climates and 40–60 days in oceanic climates, some areas becoming frost free. Precipitation increases of ten percent permit plant growth to be extended by 4 to 15 days. Ten percent decreases give a decline of about 15 days.

    1. Page 579

      In the last few decades, the international insurance industry has been confronted with a dramatic increase in the frequency of major natural disasters. In addition to the resulting problems with regard to capacity and loss reserves, both preventive planning and the proper adjustment of catastrophe losses are gaining increasing importance. The control of insured liabilities has been introduced in a number of extremely exposed markets by a joint organization of insurers and reinsurers known as CRESTA. The present problems will be dramatically aggravated if the greenhouse predictions come true. The increased intensity of all convective processes in the atmosphere will force up the frequency and severity of tropical cyclones, tornadoes, hailstorms, floods and storm surges in many parts of the world with serious effects on all types of property insurance. Rates have to be raised and in certain coastal areas insurance coverage will only be available after considerable restrictions have been imposed, eg. significant deductibles and low liability or loss limits.

      In areas of high insurance density the loss potential of individual catastrophes can reach a level where the national and international insurance industries run into serious capacity problems. One possible solution is the involvement of governments in catastrophe pools or funds, as is the case in several countries.

      Recent case studies show the over-proportionally high participation of reinsurers in extreme disaster losses and the need for more risk transparency if the insurance industry is to fulfil its obligations in an increasingly hostile environment.

    2. Page 588

      If predicted greenhouse climate change occurs, insurance on property should be available and affordable, provided taxation deferment or other incentives are allowed to enable insurers to maintain catastrophe reserve funds.

      The greenhouse effect may cause super cyclones, rising sea levels, increased storm damage and more inland flooding. This will require the Australian community to adapt to changing climate conditions. Insurance claims cost will increase because of increased technology costs, increased extreme event frequencies and intensities.

      Greater emphasis will have to be placed upon mitigation factors and their effectiveness will be reflected in the premium rates and availability of insurance capacity. There is an ongoing need to keep appropriate statistical data and to support research and education.

      This paper discusses current problems and future challenges and suggests how they may be resolved.

    3. Page 602

      The potential climate change has two distinct sorts of implications for energy policy. It will lead to international pressure to change the present pattern of fuel use, with, special emphasis on reducing the rate of combustion of hydrocarbons. More directly, it will change the pattern and level of demand for some forms of energy, most notably space heating and cooling.

      Increasing temperatures will have a significant effect on both total electricity demand and winter peak demand in southern parts of Australia. Demand for space heating is strongly associated with ambient temperature, and domestic hot water use is also influenced by temperature. Use of electricity for summer cooling is likely to increase in Queensland, the Northern Territory and South Australia. The effects on peak demand are estimated and shown to be significant. The effect on combustion of fossil fuels cannot be calculated until the influence of climate change on available hydro-electricity has been estimated.

      Australia faces severe problems of adjustment if there is international pressure for reduced use of hydrocarbons, as structural factors largely determine our very heavy use of transport fuels. While more effective use of public transport is possible, our urban structure imposes serious limitations on our flexibility. International pressure to reduce hydrocarbon use and these limitations together constitute a significant force for fundamental change. Although there are formidable obstacles to the task of either reducing energy use or replacing fossil fuels by other energy sources, the changes to the climate now being predicted are highly likely to stimulate a serious attempt to alter the current pattern of energy use.

    4. Page 613

      Predicted climatic changes resulting from the greenhouse effect are likely to impact on electricity generation in New South Wales, Australia, in the following ways:

      • Decrease electricity demands for winter heating.

      • Increase electricity demands for summer air-conditioning.

      • Increase pumping loads from land-drainage systems.

      • Bring about a small decrease in steam plant efficiencies.

      • Sea level rises of 140 cm will not cause flooding of station facilities nor directly affect station operations.

      • Reduced snowfalls on the Snowy Mountains will affect the seasonal distribution of runoff but this will be accommodated by changed reservoir operations.

      • Increased rainfalls could decrease irrigation pumping loads but this may be compensated by an extension of irrigation areas.

      • Increased rainfalls and stream flows will improve the security of water supplies at inland stations which utilise wet cooling systems and increase energy productions at hydro-electric stations.

      • A higher incidence of cyclonic storms will increase the incidence of transmission line tower failures due to wind loading but this should not significantly lower reliability of supply as the higher structural stresses will be accommodated by design margins.

      Concern about the increasing carbon dioxide concentrations in the atmosphere will generate pressures of greater utilisation of renewable energy sources (hydro, solar, wind and waves), but their limited energy production capability and/or their high costs mean that they will prove to be incapable of replacing fossil-fuel fired generating plants in New South Wales. Nuclear energy is the only proven electricity producing system which does not emit carbon dioxide to the atmosphere and which can produce electricity consumption levels at prices reasonably comparable to fossil-fuel plants.

    5. Page 624

      The transmission of mosquito-borne diseases is dependent on the close association of mosquito vector and vertebrate host populations. In Australia, the prevalence of vector populations correlates closely with observed patterns of disease transmission. However, both the vertebrate host population and vector numbers must be above threshold densities for transmission to be maintained. The major epidemiological factors are primarily under climatic control.

      The most important mosquito-borne diseases in Australia are the human arbovirus dengue, and the zoonotic arboviruses Murray Valley encephalitis virus (causing Australian encephalitis) and Ross River virus (causing epidemic polyarthritis). Historically, the parasitic diseases malaria and filariasis have also been significant.

      If the greenhouse effect increases rainfall and temperature, it can be expected to influence the seasonal and geographical abundance of the major vector species and vertebrate hosts. In tropical Australia, the impact of these changes should (a) increase receptivity and thence vulnerability to malaria, (b) increase the incidence of epidemic polyarthritis, and (c) extend the geographical area of endemicity of Murray Valley encephalitis virus and possibly the frequency of Australian encephalitis outbreaks, particularly at the southern boundary of the monsoonal influence. It may have an effect on the incidence of dengue, but this could be limited as the vector mosquito breeds in domestic container habitats which are often artificially maintained by man, and are thus independent of rainfall.

      In temperate Australia, the increased winter temperatures and summer rainfall will extend the season favourable to Culex annulirostris, the dominant vector species. Breeding of this species could extend from mid-September to mid-May permitting much greater summer populations to be reached. This could favour increased incidence of epidemic polyarthritis. Possible changes to the incidence of Australian encephalitis are less clear. If increased spring and summer rainfall permit the required threshold associations of vectors and hosts to be exceeded more frequently, Australian encephalitis outbreaks/epidemics may become more frequent. On the other hand, if this threshold is exceeded only in those years with major spring floods associated with intense El Nino/Southern Oscillation variations, then the incidence of Australian encephalitis epidemics will depend on the changes to the El Nino/Southern Oscillation resulting from the greenhouse effect.

    6. Page 638

      Planning involves the predictions of what the future holds and preparing the community’s response in order to achieve certain goals. Some parts of the future we cannot control; if we are to achieve our goals, we must be able to adapt to changing circumstances. Sound planning must include an element of flexibility to enable appropriate responses to circumstances beyond planning control.

      This paper describes a number of components of water planning in Victoria, Australia, with particular reference to regional water management planning, taking the south western region of Victoria, as a case study.

      The paper examines the potential of climatic change to affect various elements in the Regional Water Management Plan, with emphasis on effects on the sources of water, and on effects on the urban and environmental demands for water in the Region. It also provides an outline of some of the difficulties in planning for maintenance of environmental values under changing climatic conditions.

      The paper then considers means of predicting the magnitude and significance of such effects for water planning in Victoria. Greater accuracy in prediction is essential for sound planning.

    7. Page 648

      The World Meteorological Organization and related expert groups have recently emphasized human impacts of impending atmospheric warming, caused by increasing levels of greenhouse gases. These impacts can only be evaluated when coping strategies are known. In this context, a study was carried out to investigate preparedness for decision making at the local scale.

      A preliminary assessment is made of problems associated with potential sea-level rises in the coastal community of Redcliffe (Queensland, Australia), including:

      • The nature of the risk to specific areas.

      • The land use and infrastructure at risk.

      • Economic, social and managerial consequences of the various hazard dimensions.

      These dimensions are evaluated against the perceptions and envisaged responses of the community to a hazard of low imaginability in a technologically advanced society. The paper reports on the level of awareness in a stratified sample of the local population, and a Delphi type survey among a group of key community representatives and decision-makers.

      The main results discuss the perceptions of decision makers as to their responsibilites for adjustment to the hazard, the relationships between expected impacts and planning horizons, and different evaluations of impacts by sectional community interests.

    8. Page 665

      The global climate is now thought to be warming as a consequence of human activity at approximately 0.3 °C per decade. This process could lead, within a few decades, to temperatures above those experienced in all of human history. Climatic warming is occurring in a global context of severe ecological stress. Unprecedented rates of species extinction are occurring and significant evidence exists of an instability in many natural systems. Poverty in the developing world is a major factor in the developing ecological crisis.

      In facing up to the problems posed by climatic change our policy formation processes are confronted by unprecedented challenges. Some of the key characteristics of the problem involve irreversibility, uncertainty, unpredictability and interactiveness. Conventional assumptions about the desirability and nature of economic growth may have to be reviewed. In view of the grave risks imposed by unrestrained climatic warming, it is argued that a strategy responding to the problem should favour measures designed to limit the rate of climatic warming, preferably below current levels, as well as taking the necessary adaptive measures.

      Energy and resource-use policies oriented towards conservation objectives could provide significant leverage on the global warming problem. The current rate of combustion of fossil fuels places approximately 5 Gt of carbon into the atmosphere as carbon dioxide each year. Feasible fossil fuel consumption scenarios indicate that this carbon input could be reduced to 1–2 Gty’1 by the middle of the next century, whilst raising average global living standards. If fossil fuel consumption is unrestrained, carbon input to the atmosphere could accelerate to 20 Gty’1 over the same timeframe.

      Feasible options exist to control the emission of several of the major trace gases, notably chlorofluorocarbons, which are contributing significantly to the global warming. International action is necessary if a limitation strategy is to be successful. Moves analogous to the Montreal Protocol on Ozone Depleting Substances could be contemplated to control the rate of release of greenhouse gases.

      Australia would need to develop an economic strategy that reduces dependence on energy intensive and resource intensive industries. In addition, a national review of the adequacy of the current system of biological reserves and their capacity to function under changing climatic circumstances is urgently needed.

    9. Page 680

      The social control of private and public development to reduce the risk of undesirable effects and to enhance a range of benefits is generally of a statutory nature in western industrial societies. Very often the principal legislation is a single "Planning Act" which is complemented by other environmental and land use controls such as environmental impact assessment (EIA), pollution controls and broader land management legislation. The integration of all these controls constitutes the environmental planning system.

      The system counters perceived environmental risks and problems, such as may arise from the greenhouse phenomenon, by endeavouring either to reduce the risk of major damage or to remove the cause of the problem. It is a significant issue in Australia whether national, state or local governments should be the prime movers of these strategies. Economic and equity factors may discourage unilateral action by state and local governments; nonetheless administrations at this level are best placed to develop strategies to minimize undesirable effects. In the light of international obligations the Commonwealth carries the moral responsibility for reduction of greenhouse gases.

      This gives rise to constitutional issues in Australia, in particular the power of the Commonwealth to legislate in this area. Practically, however, any attempt to introduce effective planning measures will require Commonwealth, state and local government co-operation.

      Planning experience has demonstrated the ability of state and local governments to control development in areas subject to natural hazard. South Australia was the pioneer in accounting for historical rise in sea level in coastal planning. Salisbury Council is believed to be the first local government authority in Australia to take the greenhouse effect into account in planning and foreshore control. There is no practical reason why Australian planning systems cannot use similar means to address most potential environmental consequences of the greenhouse effect. However, there is serious doubt that the perceived risks associated with the greenhouse effect are sufficiently well defined or convincing to galvanise governments (local, state and national) into promulgating planning policies which will be translated into action through existing or amended planning systems.

      The method of the planning balance sheet is used to analyse the broad environmental implications of significant sea-level rise in the Adelaide metropolitan area. This illustrates the very broad range of factors that become relevant and the weaknesses of the present planning systems in tackling greenhouse issues, in particular the absence of application of EIA to government policy directly relevant to greenhouse consequences. This approach could be pursued at increasing levels of detail to assist decision makers in contingent planning to reduce greenhouse risks and to equitably distribute costs and benefits.

    10. Page 694

      No country can do much unilaterally to forestall greenhouse-gas related environmental changes. International action is needed to minimise anticipated effects, prevention having been rendered virtually impossible. A strategy of securing reductions in the production and release of greenhouse gases is needed, the components of which should include:

      • Reduction in the use of fossil fuels through the development of alternative energy options and energy conservation programs.

      • Introduction, where practicable, of emission controls for greenhouse gases.

      • Indirect policy initiatives related to population growth, agricultural practices and forestry programs.

      Significant international dialogue has begun to occur on the means of establishing and implementing such a strategy. In particular the proposed Toronto World Conference on the Changing Atmosphere (June, 1988) will provide a forum for discussion of policy issues related to the greenhouse effect.

      The recent development of an international policy relating to chlorofluorocarbons and the protection of the ozone layer (the Montreal Protocol) demonstrates that international strategies can be secured for the protection of the atmospheric environment. But the greenhouse problem presents far more intractable political and technical problems. It is essential that Australia be involved as a contributor to the growing international dialogue on policy responses to the greenhouse problem.

    11. Page 708

      Douglas and Wildavsky (1982) have recently argued that societies deliberately choose certain issues for risk assessment while others are disregarded.

      The choice is governed by factors neatly summarised in Cooper’s (1987) seven propositions concerning national precursors for policy formulation. In these terms there is scope for developing policies for coping with environmental changes associated with the build-up of greenhouse gases, but it is counter-balanced by the lack of consensus that policy makers find among scientists and among political pressure groups in general.

      In common with many other nations, our cultural awareness of the nature of environmental change gives more credence to the random than to the predictable. Public institutional response is unlikely to become overt until scientists can change this attitude by providing demonstrably valid predictions about identifiable effects such as changes in sea level or the productivity of food crops traded internationally. Australian natural disaster management practices provide part of the foundation for evolving suitable institutional responses to cope with some such changes but incorporation of environmental predictions into the machinery of government and long term planning is dependent on a change in our cultural appreciation of the nature of environmental stability.

    12. Page 725

      The greenhouse effect is an international matter. It results from changes wrought by human activity world-wide and has global consequences.

      Through international for a, Governments, scientists and other interested parties are beginning to consider global approaches to this issue. The United Nations Environment Program has been involved in greenhouse issues principally through activities related to the World Climate Program and in policy for a emanating from the 1985 Villach Conference. The OECD has flagged intentions to contribute towards the development of effective international strategies primarily relating to energy policy issues and impact assessment. In an incidental manner, the control of ozone depleting substances, now being brought about under the Vienna Convention, will have some impact on climate warming.

      Nationally, the Australian Environment Council, consisting of Commonwealth, State and Territory environment Ministers, has recognised climate change due to the greenhouse effect as being a major policy issue and has commenced a review of potential impacts.

      The Commonwealth Department of the Arts, Sport, the Environment, Tourism and Territories is involved in consideration of these matters within the Commonwealth Government and at the national level and is contributing to discussions within international for a.

      At a national level, there are three broad areas to be pursued:

      • Further research to provide regional assessments of likely climate changes and the impacts of these changes.

      • Policies to reduce the build-up of greenhouse gases in the atmosphere so as to retard the greenhouse effect.

      • Policies to deal with the effects of climate change due to the greenhouse effect, by means of minimising the impact of such changes or adapting to those impacts.

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