Greenhouse: Coping with Climate Change

Greenhouse: Coping with Climate Change

Consideration of climate change deals increasingly with impacts and responses, and therefore involves a wide range of technical issues and a diverse community of experts. One of the challenges faced is that of ensuring effective communication between these different areas of expertise. For example, climate change studies require new types of collaboration between carbon cycle modellers and economists, and between meteorologists and coastal geomorphologists. Furthermore, there is a need to distil balanced assessments ranging across many disciplines for the benefit of all policymakers.Greenhouse: Coping with Climate Change brings together the contributions of many experts to the climate change debate.

This book is a landmark publication summarising our understanding of climate change issues as they affect Oceania. It contains review papers that report on the status of knowledge, methodologies and developments; and a selection of focused papers that expand on specific issues and present significant new developments of wide general interest and relevance to the region.

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      This paper reviews changes that have occurred in the atmospheric levels of major greenhouse gases and consequent changes to heating of the lower atmosphere through the enhanced greenhouse effect. The naturally occurring greenhouse gases carbon dioxide, methane, and nitrous oxide have increased by about 27%, 140% and 10%, respectively, over the last 300 years and Over the last decade have increased at an average rate of 0.4, 0.7 and 0.3% y-l, respectively. The rapid increases in these gases that occurred after the 18th century have been due to changes in anthropogenic sources and sinks. Direct measurements in the atmosphere, and studies of source and sink processes, are now producing detailed budgets for these gases.

      Several industrially produced greenhouse gases, such as chlorofluorocarbons (CFCs), are entirely anthropogenic in origin. Until recently CFCs were increasing rapidly in the atmosphere, however, emissions of CFC-11 and CFC-12 have been reduced because of adherence to the Montreal Protocol. Increases in their atmospheric concentrations have thus slowed and are expected to stabilize and then decline before the end of the century. Hydrochlorofluorocarbons (HCFCs), used as substitutes for CFCs, and some other man-made greenhouse gases are increasing rapidly in the atmosphere.

      Ozone is a greenhouse gas which is produced by chemical reactions in the atmosphere. Emissions of CFCs have decreased ozone in the stratosphere, whereas emissions of nitrogen oxides and volatile organic compounds have increased ozone in the troposphere, at least in the northern hemisphere. Global atmospheric chemistry models indicate that changes in ozone over the last 200 years have probably contributed more to the enhanced greenhouse effect than changes in nitrous oxide or CFCs.

    2. Page 27

      One of the major constraints on present efforts to model the climatic effects of increases in greenhouse gas concentration over the last few centuries is uncertainty about the role played by atmospheric aerosol, especially sulfate particles, and by carbon-containing and other atmospheric particles. Recent analyses suggest that in the northern hemisphere the combined ’direct’ and ’indirect’ (mediated through cloud reflectivity) effects of anthropogenic sulfate aerosols may have had a cooling effect approximately equal to the warming effect of increased atmospheric carbon dioxide concentrations since pre-industrial times. Clearly this possibility is of immense significance. In this paper, current understanding of the ’direct’ and ’indirect’ roles of atmospheric sulfate particles and clouds is reviewed, and other second-order climatic effects via aerosol-induced modification of cloud microphysical properties are discussed.

    3. Page 42

      The atmosphere, oceans, ice sheets and the terrestrial biosphere are major components of the climate system. This paper focuses on climate models and climate processes associated with the terrestrial biosphere and its interaction with the lower atmosphere. Studies using atmospheric climate models have demonstrated the importance of the terrestrial biosphere, particularly with respect to the sensitivity of climate to changes in albedo, roughness and soil moisture availability. Comparisons of climate model simulations with observations have also revealed deficiencies in the land surface radiation and energy budgets as simulated in these models. These deficiencies are manifest as (i) significant model biases in annual net radiation and individual radiation components; (ii) a large range of variation in monthly and annual evaporation and sensible heat flux. Such deficiencies reflect a lack of understanding in four areas (i) surface radiation and energy budgets and the lack of long-term observations; (ii) soil hydrology where there is an inability to quantify soil water-holding capacity and difficulties with averaging over heterogeneous landscapes; (iii) vegetation, and the need for closer links between the stomatal conductance, and its control of evaporation, and photosynthetic carbon uptake; (iv) surface heterogeneity. New regional experiments on land-surface interactions and long-term observations of surface fluxes would provide additional constraints on model behaviour and progressively improve their performance.

    4. Page 56

      The global climate system consists of four main components: the atmosphere, oceans, ice and the biosphere. The modelling of the individual components is extremely demanding, and further fundamental scientific advances are required. This paper aims to provide a clear indication of any weaknesses in the component models, as applied to climate change, and present the strategies being adopted to improve these models. Problems associated with the modelling of climate change by means of fully coupled models are also discussed.

    5. Page 81

      Long climate records from deep sea sediments and polar ice caps show that the last few million years have been dominated by quasi-regular glacial-interglacial cycles. These cycles are ultimately regulated by fluctuations in high latitude, northern hemisphere, seasonal solar radiation caused by orbital perturbations. Trace gas records from ice cores reveal variations in atmospheric carbon dioxide and methane concentrations that parallel climate fluctuations. The sensitivity of global temperatures to increasing greenhouse gases (approximately 2°C for a doubling of carbon dioxide concentrations), as estimated from palaeoclimate records, is close to that derived from numerical modelling of future greenhouse warming. Comparison of records of past climate states with numerical climatic model simulations show that previous versions of general circulation models (GCMs) have not performed well in Oceania, possibly because of inaccurate sea surface temperatures, a lack of an interactive ocean, and coarse resolution. More recent GCM versions perform better with present climates, and give indications of better performance in modelling past climates.

      While palaeorecords of climate change can provide no close parallel to greenhouse warming as the primary forcing and its spatial distribution differs, they do indicate how biotic and physical systems react to climate change. The most recent warming events comparable in size to those expected in the near future led to major biotic changes. Vegetation assemblages during the last prolonged episode (8000 to 6000 BP), when temperatures were warmer (O.S-l.S°C) than present, were markedly different from those of today.

      The current climatic regime that established between 3000 and 2000 years ago is highly variable. High resolution records show some decades and centuries have had higher or lower than average numbers of warmer or wetter years, but there have been no sustained periods of highly deviant climate. The much publicised Medieval Warm Period (9th to the 14th century) and the Little Ice Age (17th to mid 19th century) do not appear as discrete events in these records from the Australia-New Zealand region. The warming of recent decades is an unusual event as shown by the long-term perspective of these records.

      Palaeorecords show the Antarctic region to be highly sensitive to warming and, with future warming, sea ice extent could be dramatically reduced. On a much longer timescale, the unstable West Antarctic Ice Sheet could be vulnerable to collapse because of the effects of rising sea levels.

      Despite an increase in detailed palaeoenvironmental records from all parts of Oceania, extraction of unequivocal climatic parameters remains an elusive goal. The interaction of climate and complex biophysical and geophysical settings is still poorly understood.

    6. Page 100

      In this study, observed trends and variability in climate and sea level for Australia, New Zealand and the south Pacific (Oceania) are presented. The results are derived from high quality, long-term climate data. It is found that annual surface air temperatures have increased between 0.4 and O.8 °C throughout most of the region in the period 1951-1993. The fewer longer temperature series from parts of the region show an increase of 0.7 ± 0.2°C of land air temperatures and of the surrounding sea surface temperature from the beginning of the century, consistent with that observed for the Southern Hemisphere. Concurrent with observed warming over the last four decades, a significant decrease in the diurnal temperature range (DTR) has occurred over significant parts of Australia, and in the central south-west Pacific, particularly in areas where cloud cover has increased. In other areas, there is little change or small increases in DTR with associated decreases in cloud cover.

      Summer precipitation increases occurred over eastern Australia. Increases occurred in the south Pacific to the north-east of the South Pacific Convergence Zone (SPCZ), whilst decreases occurred to the south-west of the SPCZ. Interannual variability in temperature and precipitation is very much driven by the Southern Oscillation throughout Oceania. Since the mid-1970s, more frequent EI Nino episodes have influenced longer term trends in precipitation.

      However the longer term warming trend observed in the sea and land temperature reflect hemispheric-wide climate warming and circulation change. Warming is also observed in surface and main thermocline waters in the oceans, with a freshening of Antarctic Intermediate water. The observed sea level rises of almost 2 mm y−1 (from tide gauges) are consistent with the observed ocean warming. The observed records of change in Oceania show some definite trends. This area provides an excellent regional monitoring platform of trends and variability in climate and sea-level in the Southern Hemisphere.

    7. Page 127

      The oceans store and transport vast quantities of heat, water and carbon. As a consequence, the rate and regional distribution of climate change on time scales longer than months is dominated by ocean processes. Of particular importance is the rate of exchange between surface, intermediate and deep waters. On time scales of several decades to millenia, climate variability is strongly controlled by the thermohaline circulation, a system of ocean currents driven by sinking of dense water at high latitudes balanced by upwelling elsewhere. The volume (and residence time) of the near-surface and intermediate-depth reservoirs is smaller than that of the deep sea, so exchange between them is important for heat and carbon storage on time scales of years to decades.

      Changes in ocean circulation can have a strong impact on regional climate. Sea surface temperature variations in the Pacific and Indian oceans, for example, are correlated with Australian rainfall. Sea surface temperature is, in turn, sensitive to changes in ocean circulation, such as the flow from the Pacific to the Indian Ocean through the Indonesian Archipelago. Similarly, the severe winter experienced in New Zealand in 1992 can be related to anomalous currents removing heat from the Tasman Sea, thereby reducing sea surface temperature.

      Recent improvements in the correction of tide gauge observations for land motion has resulted in a consistent record of historical sea-level rise. Forecasts of future sea-level rise due to thermal expansion of the ocean have been improved by taking into account the fact that heat enters the ocean primarily by advection rather than diffusion. While substantial progress in observing and modelling the ocean has been made in the last decade, reliable forecasts of future climate will require a more complete understanding of the global ocean circulation and its interaction with other components of the climate system .

    8. Page 145

      Current global climate models (GCMs) do not provide reliable detailed regional predictions of climate change. However, with a careful approach, GCM results can be used to develop scenarios of regional climate change. Such scenarios are descriptions of a range of plausible, but not all possible, future climates for a region which can be used for guidance in impact studies. This paper describes our approach to developing climate-change scenarios for Australia and New Zealand, and the caveats and uncertainties inevitably attached to them.

      The scenarios presented for mean precipitation and temperature change over Australia and New Zealand allow for three important sources of uncertainty: the range of greenhouse-gas emission scenarios considered by the Intergovernmental Panel on Climate Change as plausible, the range of uncertainty regarding the sensitivity of the global climate to increased greenhouse forcing, and differences between GCMs in the simulated regional climate change per degree Celsius of global warming. GCM results were used directly for preparing the Australian region scenarios, but for the smaller and very mountainous New Zealand, a statistical spatial interpolation technique was also used.

      For Australia in 2030, the warming scenarios are 0.S-2.SOC for inland areas, 0-1.SOC for northern coastal areas and 0.S-2.0°C for southern coastal areas. Scenarios for New Zealand are warmings of 0.S-2.0°C in inland Canterbury and Otago and 0.5–1.5°C elsewhere. Projected changes in summer precipitation for any location within Australia range from little change to as much as a 20% increase by 2030. Winter precipitation changes may be as much as 10% by 2030, but the direction of change depends on the region. Regardless of season, precipitation increases (of zero up to around 20% by 2030) predominate in the New Zealand scenarios except around Wellington, the east coast of the North Island, South Canterbury and Otago. According to these scenarios, changes in 2070 are about twice the magnitude of the 2030 changes.

      GCM results and other information are used also to provide some guidance on how other aspects of climate such as diurnal temperature range, humidity, sea level, and tropical cyclones may change. Significantly, there is considerable evidence pointing to a future increase in rainfall intensity and in the frequency of heavy rainfall events. Although quantification of this is difficult, the GCM’s results suggest scenarios of up to a halving of the return period of heavy rainfall events by 2030 and up to a fourfold reduction by 2070.

    1. Page 171

      It is predicted that there will be both positive and negative impacts of atmospheric and climatic changes on future forage and animal production. In order to examine areas of consensus and uncertainty, several specific case studies are made of grassland systems in Australia and New Zealand. Recent research on the interactive effects of increases in atmospheric carbon dioxide (CO2) and water stress in Australian rangeland grasses shows the importance of incorporating direct CO2 effects when predicting effects of future climates on plant growth. Effects of CO2 on the seasonal production and structure of temperate New Zealand L. perenne-T. repens dominated pasture communities are also expected, and are being mathematically modelled. Extreme climatic events are identified as important in determining pasture community structure, especially the invasion of subtropical (C4) grasses into temperate pastures. A new initiative within the Global Change and Terrestrial Ecosystems project is outlined. This initiative is designed to overcome the fragmented nature of much impact research by scaling fundamental biological knowledge to the farm enterprise level to interface impact analyses with economic and social consequences and adaptation responses. A case study modelling climate change impacts in tropical northern Australia is also presented as an example of interfacing impact analyses with adaptation responses. It is concluded that some specific areas of consensus are evident on predicted impacts but major uncertainties remain in quantifying the future changes. In general, it is unclear what rates of change will occur in different systems, and at what level critical thresholds exist, above which detrimental effects are accelerated. Further knowledge is needed to quantify effects of CO2, ultraviolet (UV) and climate variability on different forage plants, production systems and soils, and to identify how adaptation may modify potential direct and indirect impacts. Validated models must also be developed which describe pasture and animal productivity and make predictions at large spatial and temporal scales.

    2. Page 190

      About 65% of New Zealand’s economy is based on its natural and managed land systems and soils. Present understanding of their relative sensitivity to climate change is generally poor and largely qualitative. This paper examines the possible impacts of an enhanced greenhouse effect, with particular emphasis being given to identifying the most sensitive land systems and soils. A scenario of climate change, based on the IS92a emissions scenario of the IPCC, is used.

      The sensitivity of land systems is examined in two ways. Firstly, a first-order indication of how agroecosystems might respond to climate change is illustrated by assessing possible spatial changes in grain maize suitability. Secondly, susceptibility of land to erosion, with possible concomitant losses in productivity, is assessed against changes in precipitation. The analysis suggested only small changes in erosion severity appear likely except in critical areas where a substantial increase could result from increases in storm frequency and intensity.

      In evaluating the sensitivity of soils, the emphasis is on soil organic matter. Soil organic matter, which stabilises topsoils and stores most of the nutrients, is critically important for the sustainability of land systems. Spatially referenced data for land use, soil carbon and climate are used in a model to indicate the possible responses of organic matter to climate change for the major ecosystems of New Zealand. Reductions in soil carbon of about 5-6% per degree temperature increase were generally expected in the absence of effects from carbon dioxide fertilization and increased nutrient availability. Soils likely to reach critical minimum-threshold concentrations of organic matter over the next 60 years are identified.

    3. Page 205

      The impacts, if any, of climate change on planted forests will be apparent either as progressive change in the suitability or otherwise of particular areas for forestry, or through changes in the growth and yield of forests as a result of changing conditions.

      It is not possible to predict with any confidence the influence of climate change on the location of planted forests. Uncertainties about the effects of the expected temperature rises on physiological processes and growth, and about the influence of possible changes in rainfall patterns on water balances, limit our ability to do more than make informed guesses.

      There is strong experimental evidence, from studies on young trees, that increased atmospheric carbon dioxide (CO2) concentrations lead to increased growth. Studies with complex physiological models lead to the same conclusion for forest stands. However, all the research that has been done has used relatively high CO2 concentrations-usually double present levels, with no acclimation-so the results cannot be accepted as necessarily reflecting future forest responses. Furthermore, forests-even planted forests-are complex ecosystems within which there are many interacting processes, and there have been no long-term studies on the effects of increased CO2 concentrations on them. Nutrient cycling and availability are important factors that may determine the long-term responses to increasing atmospheric CO2 concentrations and dry mass production by trees.

      This paper reviews the basis of several well-recognised forest growth simulation models, and presents results obtained when these models were compared and used to study climate-change scenarios for sites in Australia and Sweden. The results vary because of the different structures and assumptions of the models, but generally indicate that we can expect growth increases in the short-term, when plantations are young, but that the long-term outlook is uncertain.

    4. Page 220

      The enhanced greenhouse effect is expected to cause changes in nearshore wave climates, storm frequencies and sea level over the next century, but climate change research has not yet converged on a particular scenario. Methods for identifying climatic and sea-level changes are well established, but early identification of coastal responses requires better coastal modelling and monitoring. Generalised responses to sea-level rise or shifted wave directions have been estimated from geomorphological studies but usually are not quantitatively predictive. Coastal monitoring and numerical modelling in Australia are reviewed for tidal river estuaries and barred-basin estuaries, wave-dominated coasts, low-energy coasts including those affected by cyclones, and coral islands. Palaeo data usefully extend knowledge of storm events and their coastal effects, but the value of paleo data for future prediction is questionable. Holocene palaeo data are useful for testing numerical models that predict the response of tide- dominated estuaries to a possible sea-level rise but their value in most other cases has yet to be proven. It is concluded that improved numerical modelling of coastal morphodynamics is essential but is no substitute for better coastal monitoring programs.

    5. Page 235

      Models of future greenhouse climate change have been used to produce scenarios illustrating a range of potential climatic futures. For urban areas, the most significant climatic impacts are likely to result from increased frequency of extreme events, including flooding. Both buildings and urban infrastructure are likely to experience severe effects.

      Future climate changes need to be incorporated into the strategies of policy makers. The question is how this might be done, given the generally poor record to date. Policy responses are more easily gained when future impacts are linked to phenomena whose present-day effects are widely understood. Flooding is such a phenomenon, with flood return periods (e.g. a 1-in-100 flood line) being widely incorporated into land-use and development policies.

      The paper discusses the changes to policies that need to be considered if return periods for floods are reduced, and thus the areas defined as within or outside specific flood probability lines change. It builds on recent research which links flood probability and flood damage for selected urban river catchments in New South Wales. It uses direct flood damage to buildings and contents as the focus, but also considers damage to urban infrastructure.

      There is a need for considerable further research in the area of flood damage on urban infrastructure, as well as further research on the potential impacts of changing flood return periods on both urban areas and urban policy making.

    6. Page 248

      Global climate change caused by rising atmospheric concentrations of carbon dioxide (CO2) and other trace gases may have significant impacts on the timing and magnitude of rainfall, soil moisture, evapotranspiration, and streamflow. These impacts have important implications for future water resources planning and management.

      This paper investigates the potential impact of climate change on Australia’s surface water resources. Six catchments are selected from a variety of climatic and hydrologic regimes. A stochastic weather generator is used to derive 1 000-year daily weather sequences corresponding to present day and future (doubled CO2) climates. The synthetic daily weather data are used to drive two conceptual rainfall-runoff models (IHACRES and a generalised version of Boughton’s SFB Model) that have been calibrated using historical climate and runoff data to determine the potential impact of climate change on streamflow regimes. The most prominent impacts are sizeable changes in median monthly runoff magnitudes during the high runoff periods of the year and sizeable increases in annual maximum monthly runoff. This indicates a possible increase in flood risk.

    7. Page 263

      Climate and its variation plays an important role in the supply and demand of electricity in New Zealand, where up to 80% comes from hydro generation. The supply system is controlled by runoff, which depends on rainfall, seasonal snow melt and ablation of glaciers. River flows tend to be lowest in winter, when the demand for electricity is largest, and rise in spring and summer as snow and glacier melt make significant contributions. Long-term estimates of the water balance show that average seasonal snow storage is 2500 GWh (or 330 mm). This is equivalent to 15% of total annual runoff and is similar to controlled lake storage, which is 17% of annual runoff However, there is much inter-annual variability in runoff The amount of water stored as snow is a major component of this variability and has been simulated with a snow mass balance model for each year from 1930. Sustained periods of low or high runoff are the product of large-scale forcing by anomalous atmospheric circulation patterns. Some examples of these are briefly presented. Sensitivity of the hydro-electricity supply system to changes in precipitation and temperature is simulated. Results show that for the climates likely to be experienced with greenhouse warming, the seasonal distribution of runoff will be strongly modified. Sensitivity of electricity demand to climate change is determined by statistical modelling using temperature. These simulations and sensitivity studies demonstrate that climate change will produce important changes in both electricity supply and demand and have implications for future growth and operation of the hydro-electric system.

    8. Page 281

      The development of a generic approach to pest risk analysis in relation to climate change is described. Pests are defined as any species, including arthropods, plant pathogens, disease vectors and weeds, which have adverse impacts on natural ecosystems, agriculture or human health. The potential use of generic .modelling of different taxonomic groups for pest impact assessments is discussed in the context of defining minimum information requirements, the degree of holism needed to define pest risks adequately for different purposes, and the analytical tools, databases, networks and climate scenarios required. The current status of knowledge of likely impacts of climate change on pests in Australia and New Zealand is reviewed, and examples are given of the application of an approach to impact assessments. Finally, specific needs and priorities for impact assessments in the Australasian region are discussed.

    9. Page 308

      This study examines the potential changes in species distribution predicted by a +4°C model of climate change. It suggests that if climate is the main determinant of a species distribution, then major changes in distribution could occur. The results suggest that rare biota that are climatically restricted have a strong possibility of extinction by the 22nd century. For more common species, the models predict major geographic shifts in distribution. A problem is identified as to how species can move around human- dominated landscapes to reach their future locations. A discussion is presented on the ramifications for species management of climate change.

    10. Page 325

      It is possible that climate change may stimulate population movements as people turn to migration as one strategy of adaptation. This paper tries to examine possible migration flows which may occur within and between the countries of the south-west Pacific Ocean region as a result of climatic shifts over the next few decades. The focus includes the small island states of the region, Papua New Guinea, Australia and New Zealand. Some international case studies of how societies have responded to past climatic events are considered. It is argued that the small island states appear vulnerable to climate change, with low coral atolls being most at risk. Adverse impacts of climate change will put extra pressure on Papua New Guinea and small island states which are already struggling to cope with sustainable management of their natural resources and with the demands of their rapidly growing populations for education, housing and employment.

      Regional climate change, in particular sea-level rise, may increase the numbers of Pacific islanders attempting to migrate permanently to New Zealand and Australia. Any such migration strategy is likely to entail significant medium-term health, psychological and social costs for some Pacific island migrants as they try to cope with life in Western industrialised societies. It is unlikely that gradual climate change will lead to the forced permanent migration of large populations within Australia and New Zealand over the next few decades. Populations in developed countries generally have the resources to defend major human settlements from predicted sea-level rises and to cope with climatic stress in situ. However, sustained climate change may contribute ultimately to gradual population shifts within Australia and New Zealand.

    1. Page 349

      Adaptation is a straightforward, highly robust and all pervasive strategy for coping with change. As climate varies very much more rapidly with geography and season than through time, the success and variety of human and natural adaptation to different climates is self-evident around the world. Adaptation does not require definition or explanation; it is well understood and its benefits and costs appreciated if not fully quantified or even quantifiable. Since adaptation is clearly feasible and potentially beneficial, why has it become the neglected ’Cinderella’ of climatic change? The perceived reasons include lack of economic evaluation, failure to identify sources of funds, lack of motivation, the desire not to lose impetus towards mitigation, the need to await impact (or integrated) assessment, and the lack of agreed criteria for selection of adaptive strategies. I believe that most of these ’arguments’ are more apparent than real. In this paper, I argue that most of the mystery surrounding adaptation is bunkum or camouflage. I put the case for a positive approach to adaptation. In Oceania ’climate proofing’ is a no-cost adaptive strategy offering enormous benefits.

    2. Page 377

      Decisions to plan for the potential future impacts of climate change and sea-level rise are being made every day around the coast of Australia and New Zealand. Decisions about the location of new coastal development in potentially hazardous coastal areas and hazard mitigation for existing development are a routine part of the planning processes for both countries. These decisions are being made in the face of incomplete information on both natural climatic variability and its extremes, and with considerable uncertainties in the magnitude of future greenhouse-induced climate change and sea- level rise. Because planning decisions cannot be delayed until there is complete certainty in the prediction of future greenhouse effects, uncertainties must be taken into account when planning decisions are made. The various spheres of government in Australia and New Zealand have chosen different mechanisms to take into account coastal impacts, and the attendant uncertainties. These mechanisms depend to a large extent on each country’s coastal management systems. This paper analyses the climate change and sea- level rise impact mitigation strategies adopted by the two countries. This analysis concludes that the governments of both countries use a policy-driven approach to planning for potential future coastal change, implemented through a hierarchy of regional and local plans, rules and guidelines. Despite these similarities, legislative differences are likely to result in subtle differences between the two countries in the type and magnitude of the reduction of the impacts of potential future coastal change.

    3. Page 399

      Many organisational levels from international institutions to the farmer must be involved in adapting agriculture to anthropogenic climate change. Each level has a different role to play. Governments should consider long-term scenarios and the implications for such things as population and land tenure policy, and policies that influence bank lending arrangements. Individual farmers cannot plan for highly uncertain specific scenarios eventuating decades ahead, given other faster-acting external factors influencing them. They can, however, strive for flexibility and keep good farm climate and management records to allow faster reactive responses. In the highly variable climate of Australia, this approach, combined with informed use of seasonal weather forecasts based on the Southern Oscillation Index; should permit automatic reactive adaptation to anthropogenic climate change as a spin-off from routine proactive and opportunistic responses to natural climatic variability.

      At the level of agricultural research, there are anticipatory adaptive options that can be investigated and developed. Examples are genetic modification of plant and animal species by breeding, and changes in the management of individual crop and pasture systems. For New Zealand, a strategy is proposed for iteratively relating forage species improvement and evaluation to the implications of scenarios of atmospheric and climatic change. To some extent, the yield of annual temperate crops, such as Australian wheats, may largely self-adapt to earlier springs where development is controlled mostly by the passage of thermal time. Thus breeding would need only to fine tune to the change. There are also modifications that can be made in the management of whole farm systems. However, situations may arise where it is more appropriate to alter land use than to adapt the existing land use. Hence, strategic approaches to the development of policies, institutions and infrastructure are required that can allow regional adaptation of agriculture over longer time-scales.

    4. Page 417

      Carbon sequestration by plantation forests is examined conceptually, and quantified by data obtained from New Zealand’s national estate. N ew Zealand’s plantation forests are sufficiently uncomplicated to enable key issues to be identified. Areas of critical interest for carbon sequestration are shown to be average rotation length and the age- class distribution of the plantation resource, whereas the growth rate of trees (m3ha−1y−1) and the fate of wood products are demonstrated to be of lesser importance.

      The establishment on grassland, and replanting upon harvest, of 1 ha of Pinus radiata on New Zealand pasture/and, using a regime typical of present-day practices will result in the sequestration of approximately 112 t of carbon in perpetuity. This can be viewed as a one-off movement of carbon from the air to the land surface. Some of this benefit will be lost if fossil fuels are used to process the wood, and if the wood products decay anaerobically in landfills to release methane, but there may be benefits that result from the substitution of wood for less energy-intensive products.

      Forests are considerably more complex than stands (an area of trees that is relatively uniform in species composition, age and management regime), and it is essential to understand the age-class structure of a forest in order to quantify the carbon present and to predict future levels of sequestration or emissions. Forests that are currently sinks for carbon can become sources as the age-class composition changes.

      At a high rate of afforestation (100 kha y-1), carbon sequestration by New Zealand plantation forest sinks may exceed emissions from combustion of fossil fuels from A.D. 2008-2026. Assuming that there is an upper limit of plantable land of 5 Mha, there would be a rapid decrease in sequestration from about 2045. At the more modest rate of 60 kha y-1 of afforestation, sequestration by forest sinks expands approximately in parallel to increased emissions until about 2018. After that, emissions rapidly overwhelm the capacity of sinks.

    5. Page 437

      This paper outlines potential emission-reduction strategies for ruminant methane. The simple option for lowering ruminant methane emissions by substantially reducing livestock numbers is economically unacceptable as New Zealand and Australia depend upon ruminant products for income. Ruminant methane production in both countries and the digestive processes in the rumen leading to methane formation are outlined and two possible approaches for reducing methane emissions are presented. These approaches focus on dietary and microbiological factors to take into account the fact that the problem is a microbial one as well as an animal one. One option is to increase the efficiency of both feed utilisation and production by forage-fed animals in order to reduce the amount of methane produced per unit of product. This approach involves reducing animal numbers but maintaining production levels. The other option, which does not require a reduction in animal numbers, is to target directly the microbial processes which lead to methane formation in the rumen.

    6. Page 450

      The pattern of energy use is largely determined by social factors. This is clear from comparative studies which show that the link between energy use and either climate or the scale of economic activity is complex. The same conclusion emerges from studies of the changing pattern of energy use over time in a given society. Consumer demand is not for energy as an abstract quantity but for energy services such as motive power, transport, heating and lighting. The level of demand for each of these services is largely determined by social factors. There is remarkably little evidence for the common belief that the pattern of energy use results from perfectly informed consumers making rational choices in a free market to maximise their marginal utility. In many cases, the consumer sees no price signal at the point of use. Where there are incomplete price signals, as in the case of transport fuels, energy demand is highly inelastic.

      These considerations are crucial if there is an aim of changing the pattern of energy use. Demand for energy can be influenced by price signals, by legislation or by changing social attitudes. There is a common belief, based on the scale of price changes needed to influence demand, that changing demand could result in unacceptable disruption. The available evidence simply shows that price signals are the least promising way to influence demand patterns. Changing social attitudes are the key to behavioural change and central to the acceptability of regulatory change. Thus significant alteration in the pattern of energy use is unlikely to occur without an improved understanding of the social dimensions of energy use.

    7. Page 464

      This paper is principally concerned with Australia’s largest energy-supply industries: electricity and petroleum. The fuels supplied by these industries were responsible for 31% and 23%, respectively, of Australia’s carbon dioxide emissions in 1990. Both these industries, and particularly the electricity industry, are currently the subject of intense and active policy discussion and are undergoing major changes, in the context of micro-economic reform.

      If Australia is to stabilise, let alone reduce, its emissions of greenhouse gases, these industries will have to undergo radical changes, probably involving great increases in the efficiency of use, and reductions in total demand. There will also have to be major changes in the mix of fuels used for electricity generation, and probably also for transport. There has been considerable policy research and debate about these changes. Astonishingly, the two policy debates- on micro-economic reform and on greenhouse- are being conducted in almost total isolation from each other. Where the two do come together, it is mainly in the form of inadequately substantiated claims about the positive benefits of micro-economic reform for reducing greenhouse gas emissions.

      The main implications for the oil industry of the changes required to achieve greenhouse gas emission reductions may include:

      • a stabilisation or fall in demand for petroleum products, putting pressure on the financial viability of the oil refining and marketing industry;

      • the large-scale entry of new fuels and new competitors into the transport energy market;

      • changes in the taxation and the pump price of petrol and diesel.

      The main implications for the electricity industry are that the introduction of a competitive market will introduce greater uncertainties and instabilities in relation to the balance between supply and demand. These will be exacerbated by the likely market response to the existence of substantial excess generating capacity in New South Wales and Victoria. This will make it more difficult for new, independent generators using gas or renewable energy sources to enter the market. The claimed benefits of more cost reflective pricing of electricity to consumers, as an incentive for energy efficiency and renewable energy, will apply only to the relatively small number of consumers located in remote rural areas, and have in any case been undermined by the decision of the Victorian and Queensland governments to continue cross-subsidising the price of electricity in country areas of their respective states.

      Electricity distributors may have incentives to help their customers use electricity more efficiently by means of demand-management programs, but this will occur only if they are provided with the right kind of regulatory framework. There has so far been extraordinarily little discussion of the form of regulation that will be used to protect customers, most of whom will still have no practical choice between competing suppliers of electricity. Victoria and Queensland have already said that they intend to regulate electricity distributors in a way which will give distributors strong incentives to maximise sales of electricity, and no incentive to pursue demand-management alternatives. On balance, therefore, it is probable that implementation of the competitive national market in electricity, in the form presently envisaged, will make it more difficult for Australia to reduce greenhouse gas emissions.

    8. Page 478

      Projections of energy demand in Australia under business-as-usual assumptions show continued growth, although rates are projected to decline after 2000, in line with assumptions on growth in population and GDP. Carbon dioxide emissions from the energy sector will follow a very similar pattern.

      A wide range of technical opportunities to reduce emissions of carbon dioxide from the energy sector, which will also contribute to overall economic efficiency or at least have no net costs, can be identified. These are the so-called no regrets opportunities and exist because of a range of market failures and distortions. The nature of market failures and some of the constraints on the level and rate at which emission reductions might be achieved are discussed.

      Packages of measures can be designed which will enable part of these technical opportunities to be attained. Such packages would consist of two major types of measures: micro-economic reform which would materially reduce existing distortions in the market place; and a range of energy programs aimed at addressing specific market failures. It appears to be feasible to design a package which will make a significant contribution to reducing the rate of growth in emissions in the short to medium term and to stabilising emission rates in the medium to longer term, provided that factors driving energy demand growth rates are moderated.

      In the longer term, major options on the energy supply side may offer an opportunity to reduce emissions. However, if levels of reduction in emissions significantly greater than those given in this energy-efficient scenario are required in the short to medium term, other measures such as carbon taxes will be necessary.

    9. Page 492

      In response to concerns about global warming, there is increasing interest in the potential for using renewable sources of energy to meet the world’s energy needs. This paper reviews the present use of renewable energy in Australia and New Zealand and examines the potential resources available to meet the future energy needs of both countries. Resources considered include hydro, biomass, solar, geothermal, wind, tidal and wave energy.

      Consideration is given to a variety of factors which are likely to determine the extent to which renewable energy options are used. These factors include the availability and cost of non-renewable resources, advances in renewable and other energy technologies and the severity of environmental problems (greenhouse and non-greenhouse related).

      Two future scenarios for the use of renewable energy in Australia and New Zealand are considered. One scenario assumes a continuation of recent trends relating to micro- economic reform in the energy sector and the implementation of greenhouse-related response measures which incur no net cost to the economy. The other scenario assumes that a concerted international effort will be undertaken towards stabilisation of atmospheric levels of greenhouse gases.

    10. Page 507

      The main determinants of energy use in the residential sector are householder preference and behaviour, appliance characteristics, dwelling thermal performance and energy price. The level of energy efficiency in the residential sector is well short of the economic optimum, and there are many opportunities to supply energy services at far lower economic and environmental cost. For the most part, these opportunities can only be realised through programs of selective intervention in the market.

      This paper reviews the range of programs which governments and utilities in Australia have adopted to encourage greater energy efficiency in the residential sector. Most of these are now part of the National Greenhouse Response Strategy. They include information programs, minimum performance standards and financial incentives. The programs most likely to deliver significant and cost-effective reductions in greenhouse gas emissions are those which bear directly on appliance characteristics, rather than those which target the other main determinants of residential sector energy use.

      Current issues of planning, implementation, evaluation and resource allocation between residential sector programs are also discussed.

    11. Page 520

      Five or six decades of town planning has built many Australian, New Zealand and US suburbs on the assumption of ever-growing car use. In historical terms, this Car City era is only a short period but it has extraordinary environmental and social implications, especially in terms of energy use and greenhouse gas emissions. Many European and Asian cities, by contrast, are more compact and efficient in transport and energy terms. Town planning is now looking to incorporate more of these features, which have their roots in the Walking City (up to 1850 in Europe) and the Transit City (1850-1940). The Australian city data show some positive trends, particularly in comparison to US cities, but the major progressive policies and actions continue to be found in many European and Asian cities. The principles of a ’low greenhouse gas emissions’ Future City vision include a balance of walking/cycling, public transport and ’calmed’ car usage, urban villages, and their associated land use. The role of 21st century technology in facilitating such a city is suggested, not only in transport but in the energy efficient management of water, waste, community services, communications and industry. In practice, the development of the Future City is rapidly occurring in Australian cities. In Perth, the most car dependent of Australian cities, the transport sector showed the smallest increase, next to agriculture, in greenhouse gas production between the first and second WA greenhouse gas audits. This result may well reflect the effects of urban consolidation processes and the northern suburbs railway line.

    12. Page 538

      With the coming into force of the Framework Convention on Climate Change in March 1994 and the first Conference of the Parties taking place in March-April1995, political and business interest in greenhouse policy is intensifying. Governments in Annex 1 countries are concerned about their abilities to meet the Convention’s aim of returning emissions to 1990 levels by the year 2000 and there is pressure from some countries to strengthen Convention commitments through some form of protocol.

      Greenhouse is not just an environmental issue. The Convention is potentially one of the most important trade and economic conventions ever signed, and national and international actions under the Convention will affect everyone. For Australia, which is heavily dependent on fossil-fuel exports and energy-intensive manufactures, there are particular concerns about the adverse economic impacts that could flow from any strengthening of commitments. Similar concerns apply to New Zealand, where the export sector is also dependent on energy to add value to its primary products.

      This paper examines coal’s future in a world which may be increasingly bound by measures to mitigate potential climate change. The paper contends that, pending resolution of scientific and economic uncertainties, greenhouse policy measures should be undertaken within a ’no regrets’ policy framework.

      Measures ’beyond no regrets’ may become necessary, due to either politically driven strengthening of the Convention or stronger scientific evidence of significant anthropogenic climate change. Such measures would impose substantial and differing economic burdens on Parties to the Convention and there is a need for an ’equitable burden sharing’ mechanism. The paper examines various ’beyond no regrets’ measures and their implications for equitable burden sharing, including targets, emission reduction rules, international standards, carbon taxes and tradeable quotas.

    13. Page 554

      Reducing coal-based greenhouse emissions from electricity generation could make a significant contribution towards meeting any Australian national greenhouse commitment. In this paper two issues are addressed: the costs and adjustments which would be imposed upon the Australian energy sector by a range of targets and timetables to reduce energy sector carbon dioxide emissions; and the scope for different electricity generation technologies, such as advanced coal combustion technologies, renewables and nuclear power to make a cost effective contribution to reducing carbon dioxide emissions under different scenarios. The implications for the use of fossil fuels, and particularly coal, within the Australian energy sector are examined. These issues are analysed using Australian Bureau of Agricultural and Resource Economics’s MENSA model, which is a large multi-period linear program-ming model of the Australian energy system.

      It is shown that substantial substitution away from the domestic combustion of coal for energy generation and into natural gas and renewable sources of energy is required to meet increasingly stringent emissions reduction targets. Under relatively mild constraints there is a role for new and advanced coal technologies such as integrated coal gasification combined cycle (IGCC). As constraints tighten and the implicit cost of carbon increases, however, even advanced coal technologies are forced out of the conversion sector. The introduction of a nuclear power option changes the optimal configuration of the conversion sector substantially. In particular, the availability of a large, cost effective source of baseload capacity that does not produce carbon dioxide emissions allows the model to use a mix of fuels that includes coal at substantially reduced costs.

    14. Page 570

      A number of countries have in principle committed themselves to reducing greenhouse gas emissions over the next decade. Assessing the economic implications of the likely policies necessary to achieve these goals requires a comprehensive economic modelling framework. In this paper we outline the G-Cubed model and use it to analyse the effects of alternative greenhouse gas mitigation strategies.

      G-Cubed is a multiregion, multisector, intertemporal general equilibrium model. It is unique in integrating production, consumption and financial aspects of each economy. Its current version has 8 regions and 12 sectors and can be solved for horizons of up to 100 years.

      We find that a carbon tax that is levied only in Australia involves considerable costs without any noticeable effects on global emissions. Even an OECD-wide carbon tax is not sufficient to prevent global emission from rising significantly.

    15. Page 586

      The standard framework for analysing the economic impact of carbon emtsszon abatement is the cost-benefit approach, which estimates the cost of abatement and compares it with the benefits (avoided damage) over a range of abatement options. Recognised problems with this methodology include the treatment of uncertainty, the use of a positive discount rate, and the difficulty of evaluating dynamic processes such as technological change. A major advantage of cost-benefit is its ability to utilise the quantitative results from economy-wide computable general equilibrium models.

      Results from a series of such model experiments simulating the economic effect of carbon taxes in New Zealand are compared, with particular attention paid to modelling work commissioned by the Ministry for the Environment in 1993. The results suggest that New Zealand could impose a unilateral carbon tax without causing any clear-cut damage to either its international competitiveness or the level of G D P, provided that the overall fiscal package is appropriately structured. In contrast to Australian findings, the carbon tax emerges as a more powerful instrument than an energy tax in the New Zealand case. The low, possibly negative, abatement costs estimated for New Zealand overlap with parallel studies in the USA, though most computable general-equilibrium (CGE) abatement cost estimates for the US economy are positive.

    16. Page 607

      One approach to reducing greenhouse gas emissions is to impose taxes on the use of fossil fuels. Such a policy might however cause short-run economic disruption. This issue is investigated for Australia using a general equilibrium model, ORANI-E. The short-run effects of an energy tax are shown to depend on what is done with the tax revenue, how the labour market reacts, and on substitution possibilities between energy, capital and labour. Overall, the results indicate that energy taxes need not be damaging to the macroeconomy.

    17. Page 620

      This paper is based on a report by the authors to the House of Representatives Standing Committee on Environment, Recreation and the Arts (Common and Hamilton, 1994). After considering Australia’s current situation with respect to emissions and inter- national greenhouse obligations, the alternative policy instruments that could be used to reduce carbon dioxide emissions are examined. The nature of carbon dioxide taxation is discussed and the advantages and disadvantages of a carbon tax are reviewed. Based on some modelling work on the effects of introducing a carbon tax in Australia, including projections of impacts on carbon emissions, economic growth and employment, it is concluded that, with appropriate use of carbon tax revenues, there is a prima facie case for the unilateral introduction of carbon taxation in Australia.

    18. Page 641

      In this paper, a simulation using the comparative static version of the MEGABARE model is presented. The way in which countries might share the costs of reducing global emissions is examined. Many rules have been proposed in the light of various equity criteria. However, in the literature on public goods, the concept of a cost sharing equilibrium has been developed that is the natural extension of the concept of a competitive equilibrium to an economy with public goods. Global abatement can be regarded as a public good since all economies must consume the same amount regardless of their willingness to pay.

      It can be shown that a cost sharing equilibrium will be the outcome of a bargaining process where all countries seek to maximise their own welfare. Furthermore, such an equilibrium is self-enforcing in the sense that no country can improve its welfare by seeking to alter the allocation given the response of other countries. The computation of cost sharing equilibria is illustrated using the comparative static version of MEG ABARE. To compute such equilibria, it is necessary to make an assumption about the willingness of countries to pay for global abatement. Results are presented in the case where an abatement scheme is confined to OECD countries.

    19. Page 650

      Uncertainty about the process of climate change and the ability to learn more about the process over time means that there is a sequential decision problem. A key dilemma is the optimal timing of mitigation action. Even if there was agreement about the form of the possible states of the world and their probabilities of occurring, countries and individuals may still disagree on the timing and extent of costly action. Such differences would stem from differences in attitudes toward risk and the willingness to trade off the welfare of the current against future generations.

      Uncertainty means that it would be optimal to adopt a portfolio of policies. In this paper the concern is solely with mitigation policies. There is wide agreement that ’no regrets’ options should be adopted first. However, there is much dispute about the scope for ’no regrets’ options in developed economies.

      For costly mitigation policies, it is argued that there are efficiency gains from market- based policies over a regulatory approach. The major choice is between taxes and tradable quotas. There are a number of issues on which an attempt can be made to discriminate between taxes and quotas. It is argued that no firm conclusions can be drawn in favour of one instrument or the other on all but one of these issues in the current state of knowledge. The one issue in which quotas appear to have a distinct advantage is their potential to be developed as a risk management tool.

    20. Page 662

      In recent times the Framework Convention on Climate Change and Australia’s National Greenhouse Response Strategy have been drawn up to provide avenues for international and national action on the climate change issue. Effective response on climate change requires solutions that integrate environmental and economic factors.

      The National Greenhouse Response Strategy provides a comprehensive framework for action on climate change, and includes a set of initial response measures. The paper identifies issues needing to be addressed in advancing the national greenhouse response, particularly in the areas of improving knowledge about climate change, monitoring and analytical tools, greenhouse mitigation measures, and community understanding.

  3. Page 681