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Greenhouse gas emissions: Australia’s emissions from all sectors, including land use change, have risen from around 550 million tonnes of carbon dioxide equivalents (MtCO2eq) in 1990 to around 600 MtCO2eq in 2007 (CO2eq is the unit used to compare the warming effects of different GHGs, such as CO2, methane and nitrous oxide, over a 100-year period; DCC, 2009a). There have been three main contributors to emissions over this period: energy, agriculture and land use change (Figure 2.6). The largest source of emissions is the energy sector, with emissions of more than 400 MtCO2eq in 2007. The dominant contributor to energy emissions is the stationary energy sector, which is in turn dominated by CO2 emissions from coal combustion (DCC, 2009a). Emissions from the energy sector have increased steadily from 1990 to 2007, rising from around half of Australia’s emissions in 1990 to more than two-thirds in 2007. Over the same period emissions from agriculture (mostly methane from ruminant digestion and nitrous oxide from fertiliser use) have been relatively constant, at around 90 MtCO2eq per year, or 15 per cent of Australia’s emissions in 2007. Land use change (including net emissions from deforestation, afforestation and reforestation) has been a declining source of emissions since 1990. This reduction in land use change emissions reflects a substantial decline in annual rates of forest clearing in Australia due to changing regulatory and market conditions (DCCEE, 2010a).
Figure 2.6: Australia’s greenhouse gas emissions from all sectors, including net land use change, from 1990 to 2007 (DCC, 2009a; DCCEE, 2010a). Net land use change includes net emissions and removals from deforestation, afforestation and reforestation. Percentages shown on the right indicate the sectoral share of total emissions in 2007 (2007 total = 597 MtCO2eq). CO2eq is carbon dioxide equivalents—the unit used to compare the warming effects of different greenhouse gases over a 100 year period; Mt is million tonnes.
At present the only land-based emission sources and sinks accounted for in the National Greenhouse Gas Inventory shown in Figure 2.6 are those due to deforestation, afforestation or reforestation of land since 1990 (DCC, 2009a). Changes in carbon stocks on the vast majority of Australia’s landscape are not included in these estimates. This land can change yearly from a net carbon sink to an emissions source. This inter-annual variation is driven primarily by climate variability, for instance drought or high rainfall, and natural disturbances such as bushfire or insect attack. These natural factors tend to dominate over influences attributable to humans, such as agricultural land management practices (DCCEE, 2010a).
Energy, population and economy: Australia’s recent (2000–07) growth rates in primary energy supply, population and the economy, together with the growth rate in CO2 emissions from fossil fuels, are all substantially higher than those in most other developed countries. Table 2.1 compares these growth rates for Australia with the average for the 23 ‘Kyoto Annex II’ developed countries, and with the world as a whole. Our recent population growth rate exceeds the world average, and our recent growth rates for gross domestic product (GDP), energy and CO2 emissions approach those for the world as a whole, which are much higher than for developed countries because of rapid growth in developing nations.
Australia is exceptional among developed nations in being a developed economy with a growth pattern for population, energy use and emissions more characteristic of the developing world.
Table 2.1: Population, gross domestic product measured by purchasing power parity (GDP (ppp)), energy and fossil-fuel carbon dioxide (CO2) emissions data for the world, Australia and 23 developed nations (the signatories to Kyoto Annex II) for the year 2007. All data from the International Energy Agency (International Energy Agency, 2009a; www.iea.org/co2highlights). Only CO2 emissions from fossil fuel combustion are shown here; these values differ from the total greenhouse gas emissions from the energy sector shown in Figure 2.6, which include non-CO2 greenhouse gases. Primary energy supply includes the energy from primary sources (fossil fuels, renewables and uranium) supplied for domestic consumption, including transport and electricity generation, but excluding exported primary energy. The carbon intensity of primary energy is the ratio of total CO2 emissions from fossil fuels to total primary energy supply; carbon intensity of electricity and heat generation is the ratio of CO2 emissions from fossil fuels combusted for electricity and heat generation to the output of electricity and heat. Growth rate comparisons between Australia and developed nations are highlighted in red. Growth rates are per cent growth per year. $US2000 is US dollars in 2000, y is year, PJ is petajoules or 1015 joules, MtCO2, tCO2, gCO2 are million tonnes, tonnes or grams, respectively, of carbon dioxide, k$ is thousand US dollars in 2000, pers is person, kW is thousand watts, MJ is million joules, MWh is million watt-hours.
Water use: Australia’s per-capita water consumption of 1200 kL per year is among the highest in the world (Figure 2.7), largely because of Australia’s substantial irrigation industries, and food and fibre exports relative to a small population.
Figure 2.7: Per capita water consumption by sector in selected countries (FAO, 2010). Municipal consumption includes all water delivered through municipal water distribution systems (household, commercial and industrial users supplied by the municipal water system); agricultural consumption is water consumed as irrigation or for livestock purposes and does not include rain-fed agriculture; industrial consumption is water self-supplied by industry, including water consumed by the electricity (not hydroelectric), gas and manufacturing sectors; kL/pers/y is thousand litres per person per year.
Most Australian water consumption is by the agriculture sector (Figures 2.7 and 2.8), which accounts for about 70 per cent of consumption nationally. Municipal consumption (including both household and non-household uses) accounts for about 17 per cent and industrial consumption for the remaining 13 per cent (ABS, 2006). The largest contributor to municipal consumption is household use (Figure 2.9): typically 100 000 litres per person per year, with substantial variation between cities.
Water consumption is sensitive to water availability. There is a tendency for consumption to fall in dry years, illustrated in Figure 2.9 by the decreased municipal consumption in southern Australian cities (Sydney, Melbourne, Canberra, Adelaide and Perth) in a dry year (2004–05) compared with a wetter year (2000–01) (ABS, 2006). There was a similar decline in agricultural water consumption over the same period (Figure 2.8).
Figure 2.8: Australian water consumption by sector for the years 2000–01 and 2004–05 (ABS, 2006). Consumption is water used but not returned to the environment or supplied to another user for re-use. Agriculture includes water used for stock purposes, irrigation of crops and pastures, services to agriculture, hunting and trapping and the forestry and fishing sector; household includes all water used for domestic purposes, including gardening; water supply includes water consumed or lost during the supply process and water consumed by sewerage and drainage services; industry includes mining, manufacturing and other industries; electricity and gas excludes in-stream use for hydroelectricity generation. GL is billion litres.
Figure 2.9: Per capita municipal water consumption in Australian cities for the years 2000–01 and 2004–05 (WSAA, 2005). Municipal water is all water delivered through municipal water distribution systems; total municipal consumption comprises household consumption (all domestic uses) and other municipal (commercial, industrial and other water users supplied by the municipal system); kL/pers is thousand litres per person.
A similar response in water consumption has been observed over the last several decades. Figure 2.10 shows trajectories for Australian population and electricity consumption together with municipal water consumption in Melbourne, for a period of nearly 50 years (1961–2009). Through this period Australia’s population has more than doubled, its electricity consumption has increased 12-fold and electricity consumption per person has grown six-fold. By contrast, total water consumption in Melbourne increased from 1961 to 1980, changed little between 1980 and 2000 and fell thereafter, as water constraints came into effect. Melbourne water consumption per person has fallen significantly since 1980, with most of the recent (post-2002) fall being associated with water restrictions. Thus, per capita water use in Melbourne has fallen over the past 30 years, largely due to the success of demand management programs introduced during a period of drought in the early 1980s. These programs included user-pays water pricing, regulation (such as for dual-flush toilets) and public campaigns to change water-use behaviour.
The message is that growth in water consumption in southern Australia has been much slower than growth in energy consumption. Urban water consumption per person is now decreasing in response to water pricing and efficiency measures, in contrast with electricity consumption and GHG emissions per person (Table 2.1), which continue to increase.
Figure 2.10: (top) urban water consumption in Melbourne, together with Australian population and Australian electricity consumption, all scaled to 1 in 1990, for comparison in relative terms; (bottom) urban water consumption per person in Melbourne and Australian electricity consumption per person, scaled to 1 in 1990. Population data from ABS (2008a), with updates; electricity data from ABARE (2009a); water data from Melbourne Water, as reported by Sachdeva and Wallis (2010).
Constraints on greenhouse gas emissions and water availability
Australia faces constraints on both GHG emissions (if risks from climate change are to be kept low) and on water availability. These constraints are already significant and are expected to tighten as population rises.
It is well known that water is a finite natural resource because its supply from nature is limited. If effective action is to be taken to reduce the risk of dangerous climate change, cumulative emissions of CO2 (the most important GHG leading to human-induced climate change) must also be considered finite. To limit global temperature rise to any particular value, there is a cumulative cap on global CO2 emissions over the coming century (Allen et al, 2009; Meinshausen et al, 2009; Raupach and Canadell, 2010). This means that future CO2 emissions are effectively a finite natural resource (see Box 2.1). Small emissions of CO2 (and other GHGs such as methane) will be possible after the cap is reached, but these allowable, long-term emissions are much lower than current emissions and so do not affect the challenge of staying below the cumulative CO2 emissions cap.
There is an important difference between water availability and CO2 when each is regarded as a finite natural resource. The cap on water consumption arises from a constraint on the input from nature to human activities, which cannot be exceeded. The cap on CO2 emissions is a constraint on the output of CO2 from human activities to nature and is a matter of human choice—essentially between a pathway with continued high emissions and high risks of severe climate impacts, and a low-emission pathway in which risks from climate impacts are much lower.
At the level of individual nations, including Australia, there is a further critical choice about emissions constraints: how should the world share the remaining capped emissions, accounting for differences in development levels and trajectories among nations? In the present situation, where efforts to reach a global agreement are proceeding only slowly, nations need to make that choice for themselves. However, they do so with knowledge of the choices made by other nations and, consequently, the relative contributions of all nations to meeting the global challenge. This forces a degree of global cooperation between nations wanting to minimise the domestic impacts and costs of climate change. Australia is very much a part of this process; therefore, an appropriate contribution by Australia to the global greenhouse mitigation challenge is important.
To assess the magnitude of the connected constraints facing Australia for emissions and water, Figure 2.11 shows recent and predicted future trends in Australia’s population, CO2 emissions, and rainfall and runoff in southeast Australia, at 10-year intervals from 2000 to 2050, in a scenario consistent with a ‘2 degree world’ (see Section 2.2 for a discussion of the impacts in Australia of a 2 degree rise in global temperatures). All quantities are scaled to 1 in 2010 (grey bars) to aid comparison.
The future trajectory for CO2 emissions shown in Figure 2.11 is a possible course consistent with Australia acting with other developed nations to achieve emissions reductions aimed at limiting global temperature rise to 2 degrees (see Appendix A and caption of Figure 2.11 for details). To meet this challenge, Australia’s total GHG emissions (relative to 2000 levels) would need to fall by about 45 per cent by 2030 and over 85 per cent by 2050. Emissions per person, relative to the present (2010), would need to fall by about 65 per cent by 2030 and over 90 per cent by 2050. The steeper per capita reductions arise both because population is increasing and because emissions have already risen from 2000 to 2010.
Southern Australia is a region where water stress is expected to increase rapidly (Vorosmarty et al, 2000), consistent with the Australian climate projections in Section 2.2. The trajectory in Figure 2.11 for rainfall in southeast Australia (Victoria and southern NSW) represents a median fractional decrease of about 3 per cent by 2030 and 6 per cent by 2050. There is very large uncertainty in rainfall predictions, so these numbers are illustrative only, but they are broadly consistent with the projected climate changes shown in Figure 2.4 and Figure 2.5, and with other estimates from climate projections (CSIRO, 2008; Chiew et al, 2009).
The fractional changes in runoff are much greater than in rainfall, because of the ‘rainfall-runoff amplifier’ in Australian landscapes (a 10 per cent decrease in rainfall leads to a 30 per cent decrease in available water in river flows (runoff); see Section 2.2).
The lower part of Figure 2.11 shows the trends in CO2 emissions per person, rainfall per person and runoff per person. Per capita emissions, rainfall and runoff decline more rapidly than the corresponding totals because the population is increasing. In particular, water availability per person (from runoff) is likely to fall over the coming decades by around 28 per cent to 2030 and 45 per cent to 2050. These steep declines are the result of population increases and also declining total water availability in southern Australia as a result of climate change.
In summary, Figure 2.11 shows that constraints on CO2 emissions and water availability place downward future trends on these resources, against a background of a growing population.
Figure 2.11: The upper panel shows Australia’s projected future population and CO2 emissions, and projected future rainfall and runoff in southeast Australia (Victoria and southern NSW) in a scenario consistent with Australia acting with other developed nations to limit global temperature rise to
2 degrees. Coloured bars represent 10-year intervals from 2000 to 2050. All quantities are scaled to
1 in 2010 (grey bars).
Bars for population represent the middle ABS population scenario (scenario B: 34.0 million in 2050), with ranges showing high and low scenarios (A and C) (ABS, 2008b).
The trajectory shown by the bars for CO2 emissions is consistent with Australia having a share of 0.6 per cent of a cumulative quota of all global CO2 emissions from 2010 onward. The range lines on the emissions bars represent Australian shares of 1.3 per cent (upper) and 0.3 per cent (lower), which are the shares that Australia would receive if the cumulative CO2 quota were to be allocated to nations according to distribution of current CO2 emissions (giving 1.3 per cent to Australia) and distribution of population (giving 0.3 per cent to Australia), respectively.
Bars for rainfall represent a decrease in southeast Australian rainfall of −8 per cent per degree of global warming. The upper and lower ends of the range lines, respectively, represent models in which rainfall increases by 4 per cent per degree of global warming or decreases by 20 per cent per degree of warming. These rainfall predictions correspond approximately with published rainfall scenarios for southeast Australia (CSIRO, 2008; Chiew et al, 2009).
Percentage changes in runoff amplify percentage rainfall changes three-fold (Zhang et al, 2004; Raupach et al, 2009).
The lower panel shows the resulting per capita changes in Australian CO2 emissions and southeast Australian rainfall and runoff, assuming population increases according to the middle ABS population scenario (ABS, 2008b).
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