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Expert Working Group Members
Dr Michael Raupach FAA FTSE (Chair)
CSIRO Fellow, CSIRO Marine and Atmospheric Research
Professor Kurt Lambeck AO FAA FRS (Deputy Chair)
Research School of Earth Sciences, The Australian National University
Professor Matthew England
Co-Director and ARC Federation Fellow, Climate Change Research Centre, The University of New South Wales
Dr Kate Fairley-Grenot FAICD
Chair, Rural R&D Council and Director, BCP Investments
Professor John Finnigan FAA
CSIRO Marine and Atmospheric Research
Dr Evelyn Krull
Senior Research Scientist, Carbon and Nutrient Cycling, CSIRO Land and Water
Professor John Langford AM
Director, Uniwater, The University of Melbourne
Associate Professor Keith Lovegrove
Group Leader, Solar Thermal Group, The Australian National University and Head, Solar Thermal, ITPower (Australia) Pty Ltd
Dr John Wright FTSE
Principal, Wright Energy Consulting
Professor Mike Young
Executive Director, The Environment Institute, The University of Adelaide
2. Energy-Water-Carbon Intersections
This section describes the intersections between energy, water and carbon, including the realities that shape the system, the implications of climate change, recent trends in Australia’s GHG emissions and water use, and constraints on GHG emissions and water availability.
2.1 The challenge
Energy, water and carbon are each central to the economic, social and environmental health of all humankind (Figure 2.1). Energy and water are essential for practically all activities. We, and the biosphere we inhabit, are carbon-based life forms. In the industrial era, carbon has acquired another significance as the primary fuel for energy systems based on fossil fuels (coal, oil and gas). In recent decades, the resulting build-up of carbon dioxide (CO2) and other GHGs in the atmosphere has begun to warm the earth’s climate—a trend that will continue to be driven as GHG emissions continue to increase. This climate change, in turn, is interacting with population growth to increase stresses on Australia’s water supplies, along with food production and the environment.
Figure 2.1: Energy, carbon and water are central to the interaction between the natural environment (left) and human society and economy (right). Energy and water are both vital for all human activities (A, B). Energy for human use is derived primarily from fossil fuels and other non-renewable sources including nuclear energy (C) and from renewable sources (D). Water for human use is dependent on the natural water cycle (E). Fossil-fuel-derived energy consumption leads to the build-up of carbon dioxide and other greenhouse gases in the atmosphere (F), which is changing the earth’s climate (G) and influencing water availability, ecosystem function and agricultural productivity (E, B). There are also interactions between water supply and energy supply because energy systems use water and water systems use energy (H). Many more connections could be shown in this figure.
Three basic realities underlie the intersections between energy, water and carbon in Australia. First, energy, water and carbon are deeply connected in every aspect of life and society, through both supply and consumption. Intersections through supply arise because our energy systems use water, our water systems use energy, and current energy generation is GHG intensive. Most land uses for food and fibre production, or for carbon sequestration, also require energy and water. Intersections through consumption arise because energy use and GHG emissions have historically increased with wealth—a connection no major economy has yet broken (Raupach et al, 2007).
The next reality is that of human-induced climate change. To keep climate change below dangerous levels, global and national limits on GHG emissions are needed. This is a particular challenge for Australia, with its present strong reliance on GHG-intensive energy sources.
Third, Australia faces strong constraints on water availability, particularly in southern regions, because of natural geography. Rainfall over most of Australia is low and variable. In addition, the available water per person in southern Australia is likely to fall over the next 20 years, both because of population increases and because total water availability in this region is likely to decline further as a result of climate change.
At the highest level, these three realities shape the nature of energy-water-carbon intersections in Australia. There will be increasing future demands for energy and water because of population and economic growth, which are linked to goals for the wellbeing of the nation and its inhabitants. On the other hand, there are future constraints on both GHG emissions and water availability. Constraints on emissions are imposed by the emission trajectory chosen by Australia, in response both to global agreements and to assessments of the risk posed by the impacts of climate change on Australia. Constraints on water availability are already significant and are likely to become more severe (in southern Australia, the home of most of the population) depending on the extent of global climate change.
These fundamental connections between energy, water and carbon will strongly influence the development of Australia over coming decades. As a nation, we seek a mix of energy sources that will meet demand while keeping below the emissions constraint, and we seek to bridge the gap between water supply and demand in the face of population growth and likely decreases in rainfall.
Because energy, water and carbon are so tightly linked, attempts to address a problem in one area without regard for its implications elsewhere can have unintended consequences that will often make matters worse overall. For instance, we could bridge part of the water gap with desalination, but at the cost of increasing energy demand. We can relax the emissions constraint by sequestering carbon in the land, possibly at the cost of decreasing water availability. These interactions are so pervasive that a central theme of this report is the search for integrated solutions.
Finding a path through these often conflicting requirements is the challenge posed by the intersections between energy, water and carbon.
2.2 Climate change and its implications for Australia
Climate change and its causes: Human-induced climate change is caused primarily by the build-up in the atmosphere of GHGs as a result of human activities. These gases include water vapour, CO2, methane, nitrous oxide, ozone and some synthetic gases. All of these (except the synthetic gases) occur naturally and make life on Earth possible by insulating our planet’s surface against the chill of space—this is the ‘natural greenhouse effect’. The concentrations of most of these gases are being directly increased by human activities, causing extra warming—this is the ‘enhanced greenhouse effect’, the main driver of human-induced climate change. Water vapour, although it makes the largest contribution to warming, is not directly influenced by human activities but rather responds to (and amplifies) the effects of changes in the atmospheric concentrations of other gases (AAS, 2010).
Of the gases contributing to human-induced climate change, CO2 is the most important (accounting for a large fraction of all the climate forcing due to these gases), followed by methane and other gases (Hofmann et al, 2006; IPCC, 2007a). The global sources of increasing CO2 in the atmosphere are emissions from fossil fuel combustion and industrial processes, accounting in 2008 for about 88 per cent of total CO2 emissions, and emissions from land use change, which account for the remaining 12 per cent (Le Quere et al, 2009). Global CO2 emissions from fossil fuels have increased nearly exponentially for more than a century, with particularly high growth over the decade 2000–09 at over 3 per cent per year (Le Quere et al, 2009). Global CO2 emissions from land use change have been approximately steady for the two decades since 1990, but there are indications in recent data of a decline in recent years (Le Quere et al, 2009).
Evidence for climate change: There are multiple lines of evidence that the earth has warmed by about 0.8 degrees since pre-industrial times, and that GHG emissions from human activities are a primary cause. If GHG emissions continue to increase at business-as-usual rates, further warming of several degrees is expected to occur, accompanied by many other climate changes including changes to rainfall patterns, sea levels, ocean currents, ice sheets, ecosystems, food production patterns and much more. These conclusions are the outcome of decades of research and thousands of observation-based and model-based studies, synthesised and assessed by the 2007 Fourth Assessment of the Intergovernmental Panel on Climate Change (IPCC, 2007a). A recent report by the Australian Academy of Science (AAS, 2010) has documented the evidence base for the broad scientific findings of climate change science over the past century and identifies the remaining uncertainties. Uncertain aspects include detailed projections of regional climate change and the magnitude and timing of climate thresholds and tipping points (sudden changes in state from which it is difficult to recover). It is important to note that uncertainties work in both directions: future climate change may be less severe than current best estimates, or it may be more severe.
Australian climate trends over past decades: Climate change is already occurring in Australia. The continent has warmed over the last century at a rate which has been greater in the latter part of this period (Figure 2.2). The warming from 1960 to 2009 was about 0.7 degrees (CSIRO and Bureau of Meteorology, 2010), which is greater than the mean global warming over the same period.
Trends in rainfall over recent decades indicate drying in the southwest and east (Figure 2.3). Possible causes of these trends include both natural climate variability and human-induced climate change, with increasing evidence that human-induced climate change is at least part of the cause (Nicholls, 2004; Larsen and Nicholls, 2009; AAS, 2010; Timbal et al, 2010).
Figure 2.2: Historical trends in Australian annual temperature (°C/decade) over the periods
1910–2009 (left) and 1960–2009 (right). Bureau of Meteorology trend maps are available at
Figure 2.3: Historical trends in Australian annual rainfall (in mm per decade) over the periods
1910–2009 (left) and 1960–2009 (right). Bureau of Meteorology trend maps are available at
Runoff and stream flow in southwest Australia have declined strongly from previous average levels since the 1970s. In southeast Australia, runoff and stream flow have declined since the 1990s. Flows in the Murray River have been at historically low levels through the period 2000–08 (CSIRO, 2008).
It is important to be aware of the ‘rainfall-runoff amplifier’, which causes proportional changes in runoff to be about three times greater than changes in rainfall in typical Australian conditions (Zhang et al, 2004; Raupach et al, 2009). For example, a 10 per cent decrease in rainfall would lead to a 30 per cent decrease in available water in river flows. This is a basic hydrological property of landscapes that occurs because the drier the conditions, the greater the fraction of the available soil water used by vegetation (trees and grasses) as transpiration. Informally expressed, the vegetation gets the ‘first drink’ from the available water. This rainfall-runoff amplifier is the largest single contributor to recent historically low flows in the Murray–Darling Basin (Raupach et al, 2009).
Future climate change in Australia: Figures 2.4 and 2.5 show the changes in patterns of temperature and rainfall across Australia in a ‘2 degree world’ and a ‘4 degree world’, respectively. These ‘worlds’ represent scenarios in which increasing GHG concentrations result in global temperature increases of 2 and 4 degrees Celsius greater than the average in 1980–99. These maps were calculated from climate projections obtained with multiple climate models used in the IPCC Fourth Assessment (IPCC, 2007a; IPCC, 2007b), assuming a ‘business-as-usual’ emissions scenario with high GHG emissions through the twenty-first century (the ‘A2’ scenario). The maps show the changes in temperatures and rainfall across Australia (relative to 1980–99) at the time when global average warming reaches 2 degrees (Figure 2.4) or 4 degrees (Figure 2.5) above the 1980–99 global average. Under the assumed emissions scenario, global warmings of 2 and 4 degrees (relative to 1980–99) are reached by around 2050 and 2100, respectively, with the exact time depending on the climate model.
Figure 2.4: Projected changes in surface air temperature (°C) and precipitation (%) for Australia, under a high-emission, ‘business-as-usual’ scenario for greenhouse gas emissions through the twenty-first century (the ‘A2’ scenario), at the time when global temperature reaches 2 degrees (2 deg) above the 1980–99 average (a climate which occurs around 2050 in these projections). Upper and lower panels show projected changes in summer (Dec, Jan, Feb) and winter (Jun, Jul, Aug), respectively. The maps show average results from multiple climate models used in the IPCC (2007) Fourth Assessment, averaged for this report as follows: projected changes are calculated as the difference between the 20-year average during the period when 2°C of warming is first attained and the corresponding average value during 1980–99. For the precipitation panels, stippling denotes areas where the models show strong agreement (where the magnitude of the average change exceeds the variability between models as measured by the inter-model standard deviation). For the temperature panels there is no stippling because all regions show strong agreement.
Figure 2.5: Same as Figure 2.4, but for 4 degrees (4 deg) of global warming relative to 1980–99, under a high-emission, ‘business-as-usual’ scenario for greenhouse gas emissions through the twenty-first century (the ‘A2’ scenario), at the time when global temperature reaches 4 degrees above the 1980–99 average (a climate which occurs around 2100 in these projections).
Temperatures are projected to increase over Australia, broadly in line with global increases. The distribution of projected average warming generally agrees well between different climate models. Over southern Australia warming is projected to be greater in summer than winter, which will pose challenges for bushfire management and emergency services. Extreme heat wave events are expected to increase over much of Australia (CSIRO and Bureau of Meteorology, 2007).
Australian rainfall is projected to decline in the south while increasing in the north (CSIRO and Bureau of Meteorology, 2007; CSIRO, 2008). The decline in southern Australia (mainly in Victoria, southern NSW and southwest WA) is projected to occur mainly in winter and to be more severe with every additional degree of global warming. For example, percentage rainfall declines over much of southern Australia are typically two or three times larger in a 4 degree world compared to a 2 degree world. Put another way, a doubling in the global warming caused by GHGs would double or triple Australia’s percentage rainfall reduction over southern regions.
Over most of northern Australia, rainfall is projected to increase. The most widespread increase is expected in summer, when higher rainfall is also expected over much of southern Queensland and northern and eastern NSW.
Model agreement for changes in rainfall is in general weaker than for temperature changes, particularly for projected rainfall changes over Australia’s interior. The strongest agreement between models for changes in rainfall is for the projected winter drying over the southern fringe of the continent and the projected summer increase in the far north of Australia.
At a global scale, the impact of a 2 degree warming would be significant (AAS, 2010). A warming of 4 degrees would lead to massive impacts for human societies (Schneider and Lane, 2006), with a number of regions on the planet potentially hostile to human health (Sherwood and Huber, 2010). There is a high probability that human populations in many regions will be affected by shifts in food supply, shifts in water availability (droughts in some regions and floods in others), increased rates of spread of diseases, increased incidence of fire weather, and direct physical climate impacts such as heat stress. There would also be profound impacts on vulnerable ecosystems, both terrestrial and marine (Steffen et al, 2004; Rockstrom et al, 2009). The impacts of climate change will also tend to exacerbate the effects of other stresses associated with the environmental footprints of increasing human populations (Rockstrom et al, 2009; AAS, 2010).
Australia is highly vulnerable to the impacts of climate change, despite its high adaptive capacity. Among the greatest sources of vulnerability are:
2.3 Patterns of energy use, water use and emissions for Australia
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