3 Atmosphere | 2 Climate | 2.6 Outlook for Australia's climate
State of the Environment 2011 Committee. Australia state of the environment 2011.
Independent report to the Australian Government Minister for Sustainability, Environment, Water, Population and Communities.
Canberra: DSEWPaC, 2011.
At a glance
The latest State of the climate report notes that, by 2070, if growth in global emissions of greenhouse gases (GHGs) continues in line with past trends, Australia will warm by 2.2–5.0 °C. A rise of around 2 °C over just two centuries is expected to lead to widespread and significant risks to Australian natural ecosystems, water security and coastal communities. The prospects of an international agreement on a framework to stabilise global emissions at either 450 ppm (with a likely rise of 2 °C in global average temperature) or 550 ppm (with a likely rise of 3 °C) appear to be limited. Many climate scientists feel that a 2 °C increase is near to or above the level that is likely to trigger ‘dangerous climate change’.
Projections of Australia’s growth in GHG emissions to 2020 based on policy settings applying before the release of the Australian Government’s Securing a Clean Energy Futureplan showed an increase of 23% above 2000 levels. The Securing a Clean Energy Future plan aims to prompt a move away from ‘business as usual’, achieving the nation’s minimum 2020 target of a 5% cut on 2000 levels by reducing emissions by at least 159 megatonnes of carbon dioxide equivalent (23%) in 2020. However, even if national and international mitigation efforts were to increase dramatically over the next decade or two and emissions were stabilised, temperatures will remain at elevated levels for centuries to come, making adaptation to change essential.
Australia, with its highly developed economy and physical, human and social capital, is better placed than many nations to anticipate the threats and opportunities associated with climate change and to take adaptive action in the short to medium term. However, this is no reason for complacency or for delaying urgent action, particularly given the potential for feedback mechanisms to amplify or accelerate climate change and cause large step-changes in regional and global climate. Should such changes occur, adaptive strategies framed around incremental change are unlikely to be adequate to prevent major harmful impacts on key sectors.
The weight of scientific opinion [is] that developed countries need to reduce their greenhouse gas emissions by 60% by 2050 against 2000 emission levels, if global greenhouse gas concentrations in the atmosphere are to be stabilised to between 450 and 550 ppm by mid century. Garnaut,13 p. xvi
The IPCC uses the term ‘equilibrium climate sensitivity’ to refer to ‘the global average surface warming following a doubling of carbon dioxide concentrations [from pre-industrial levels of 280 ppm]. This is likely [i.e. more than 66% probable] to be in the range of between 2 °C and 4.5 °C with a best estimate of about 3 °C’.61 This best estimate has been generated from geological evidence, climate modelling and 20th century observations. Based on the estimate, stabilisation at 450 ppm CO2-e would provide a 50% probability that global mean temperature increase could be limited to 2 °C, while stabilisation at 550 ppm would likely result in a rise of at least 3 °C.89 Although the magnitude of future changes in global temperatures is important, it is the rate of change that will cause the biggest impacts. A rise of around 2 °C over just two centuries is expected to lead to widespread and significant risks to Australia’s natural ecosystems, water security and coastal communities.25
Unfortunately, the prospects of an international agreement on a framework to stabilise global emissions at either 450 ppm or 550 pm appear to be limited. Analysing developed nations’ pledges to reduce emissions made under the Copenhagen Accord of December 2009, the World Resources Institute concluded that, collectively, they could by 2020 achieve a reduction of 12–19% below 1990 levels. However, the institute noted that this was well below the 25–40% reductions that the IPCC indicated were needed to achieve stabilisation at 450 ppm and thereby reduce the risk of overshooting the goal of limiting global mean temperature rise to 2 °C (agreed under the accord and by the Major Economies Forum and the G8).90 Even at 450 ppm, the risk of overshooting is still considerable (in the range 26–78%).89
Against a background of global emissions continuing to track between the IPCC’s A1FI scenario (fossil fuel–intensive growth) and the A1B scenario (economic growth based on a balance between resource-efficient and fossil fuel–intensive industries), projections of Australia’s growth in GHG emissions to 2020, based on policy settings applying before the release of the Australian Government’s Securing a Clean Energy Futureplan, showed an increase of 23% above 2000 levels (taking emissions to 690 MtCO2-e).46,62 The Securing a Clean Energy Futureplan aims to prompt a move away from ‘business as usual’, achieving the nation’s minimum 2020 target of a 5% cut on 2000 levels by reducing emissions by at least 159 MtCO2-e (23%) in 2020.47 To achieve Australia’s 15% conditional target, a 31% (216 MtCO2-e) reduction from the projected 2020 level would be needed.
Although mitigation is central to Australia’s broad climate change strategy, at the time of writing (July 2011), there is still no bipartisan support at the federal level for a key element of that strategy—establishing a price on carbon. This is despite the view of widely respected economists such as Lord Nicholas Stern and Professor Ross Garnaut on the central importance of pricing carbon to mitigating carbon emissions, and the conclusion of the recent Productivity Commission’s research report, Carbon emission policies in key economies:93
The basic theory of externalities identifies the source of the economic problem in untaxed or unpriced emissions of GHGs. The externality requires a price for emissions: that is the first task of mitigation policy. Stern,91 p. 40
Economy-wide pricing of carbon is the centre piece of any policy designed to reduce emissions at the lowest possible costs. Garnaut,92 p. 2
… the consistent finding from this study is that much lower-cost abatement could be achieved through broad, explicit carbon pricing approaches [than from existing policies] irrespective of the policy settings in competitor economies. Productivity Commission,93 p. 155
Despite the lack of bipartisan agreement on the need to put a price on carbon, legislation needed to give effect to key elements of the government’s Securing a Clean Energy Future plan is expected to come into effect before the end of 2011, with the anticipated support of three independent members of the House of Representatives and of the Greens in the Senate. As described in Section 2.3.2, the central element of this plan is a mechanism to establish a price on carbon and drive reductions in emissions via least-cost means.
However, even if national and international mitigation efforts increase dramatically over the next decade or two, temperatures will remain at elevated levels for centuries to come.75 Mitigation of future GHG emissions is therefore aimed at limiting future climate change and avoiding catastrophic climate change tipping points, rather than returning the climate system to a pre-industrial state. Beyond mitigation, our most important strategy will be adaptation. Our capacity as a society to adapt to a changing climate will depend on many factors, in particular:
- the rate of change
- the degree of exposure to the effects of change, which will vary not only geographically and from sector to sector, but also between different groups in society
- the strength and diversity of the economy
- our capacity to innovate
- our capacity for behavioural change
- our ability to expand our knowledge base and apply that knowledge in planning and decision-making
- a willingness to accept uncertainty and not to use it as a reason for postponing necessary action.
Australia, with its highly developed economy and physical, human and social capital, is better placed than many nations to anticipate the threats and opportunities associated with climate change and to take adaptive action in the short to medium term. Areas of opportunity include sequestering carbon in the soil and via large-scale landscape revegetation programs, supporting innovation in renewable energy and energy-saving technologies, and developing highly resilient systems of agricultural production. Although it is critical that these and other opportunities are identified and seized, in some key sectors—such as natural ecosystems, coastal communities and water security—our scope for adaptation through incremental change is limited and our exposure to risk is high. This combination makes us vulnerable to a temperature rise of even 1–2 °C.
Even sectors with greater scope for adaptation (such as energy security, health, agriculture and tourism) are likely to be vulnerable if, in the absence of highly effective global mitigation efforts, temperatures rise by 2–5 °C.25 A temperature rise of this magnitude is not just a remote possibility. If the world continues along its present emissions track, Australia’s average temperature is projected to rise 2.2–5.0 °C by 2070.63
It should be noted that smooth changes are the exception rather than the norm in the climate system, which is nonlinear in nature. This means that a number of feedback mechanisms exist that can amplify or accelerate climate change, with the potential to cause large step-changes in regional and global climate. Such mechanisms include rapid melting of terrestrial ice caps and changes to the large-scale circulation of the oceans. Rapid changes in climate forcing mechanisms in the geological history of the planet have been associated with sudden climate shifts; hence, failure to mitigate GHG emissions increases the likelihood of precipitating such events. In general, dramatic climate shifts have not been factored into future climate scenarios that policy makers and economists have worked with, and our ability to adapt to such changes is largely unknown.94-96
Should such changes occur, adaptive strategies framed around incremental change are unlikely to be adequate to prevent major harmful impacts on key sectors. Instead, what CSIRO describes as ‘transformational’ change will be needed, and ‘a major scientific and societal challenge [will be] to understand and decide how, where, and when this transformational change is required’.63