In Brief | Atmosphere
Independent report to the Australian Government Minister for Sustainability, Environment, Water, Population and Communities
Australian State of the Environment Committee, Authors
(2011 Australian State of the Environment Committee), 2011
This is a summary of Australia state of the environment 2011, which is an independent report presented to the Australian Government Minister for Sustainability, Environment, Water, Population and Communities by the State of the Environment 2011 Committee
Earth is warming and large step-changes in climate may occur.
Since the release of the Fourth assessment report: climate change 2007 from the Intergovernmental Panel on Climate Change, observations and research outcomes have further confirmed and strengthened the position that Earth is warming and that human emissions of greenhouse gases are the primary cause. Internationally, there is a clear consensus among atmospheric scientists that mean global temperatures have risen compared with pre–industrial levels in 1750. In addition, a number of feedback mechanisms exist that can amplify or accelerate climate change and have the potential to cause large step–changes (sudden or major changes) in regional and global climate.
It is likely that we are already seeing the effects of climate change in Australia.
Although Australia's climate is naturally highly variable, evidence continues to accumulate that temperatures are increasing and rainfall distribution patterns are changing. Models project that, by 2030, average annual temperatures across Australia are likely to warm by 1°C (above 1990 temperatures). Drying is likely in southern areas of Australia. As the driest inhabitable continent, Australia is recognised as particularly vulnerable to climate change.
We will need both a national approach and approaches at the state and territory level to mitigate and adapt to climate change.
There is broad international consensus that major reductions in greenhouse gas emissions are necessary to minimise the extent of climate change. Per person, Australia's emissions are the largest of any country in the Organisation for Economic Co-operation and Development (OECD). The Fifth national communication on climate change sets out the Australian Government's strategic approach to climate change. Such an overarching strategy, implemented at all levels of government via a range of policies, plans and programs, is essential if we are to succeed in limiting climate change and addressing key areas of vulnerability through adaptation. Early action to reduce emissions and to deploy targeted adaptation strategies will be less costly than delayed action.
Ambient air quality in Australia's major urban centres is generally good.
National health–based standards are rarely exceeded for prolonged periods, and very high levels of pollution are usually associated with short-lived extreme events such as bushfires and dust storms. Levels of carbon monoxide, nitrogen dioxide, sulfur dioxide and lead in urban air have decreased over the past two decades, but ozone and particle levels have not declined. Prospects for reducing levels of these two pollutants will depend on factors such as improved vehicle technology, the extent of ongoing low–density suburban development, the availability of reliable public transport and the impact of climate change.
Despite this broadly favourable situation, the impact of urban air quality on health is still of serious concern.
There is clear evidence that periods of poor urban air quality impact adversely on human health. One source estimates that urban air pollution accounts for 1% of deaths and illness in Australia, with some 3000 deaths attributable to this cause in 2003 — nearly twice the national road toll. Research indicates there is no threshold below which key pollutants such as particles, ozone and sulfur dioxide have no health effect. This means that sensitive individuals, such as asthmatics and people with respiratory or cardiovascular disease, may be affected even when air quality standards are met.
Despite the success of the Montreal Protocol in controlling ozone depleting substances (ODSs), depletion of stratospheric ozone will continue for some decades.
Concentrations of chlorofluorocarbons and other ODSs in the atmosphere have been decreasing since the mid–1990s, but many of these substances are long lived and will continue to affect stratospheric ozone for some decades. Nevertheless, the prospects for recovery of the stratospheric ozone layer by around mid-century continue to be good.
State and trends
Over the relatively short span of 250 years, and for the first time in human history, we have changed and are continuing to change the composition of the atmosphere on a global scale. Levels of carbon dioxide, the most important greenhouse gas (GHG), have increased by around 39% above pre-industrial levels, principally due to burning fossil fuels. This has led to a clearly defined trend of increasing average global temperatures, and there is growing evidence of consequent changes in the complex interlinked atmospheric, oceanic and terrestrial processes that shape climate at global, continental and regional scales.
From 1970 to 2010, Australia's mean daily temperature rose in almost all parts of the country. Although total annual rainfall declined over much of eastern Australia and south-west Western Australia, increases were observed in central and northern Western Australia and in the north&ndashwest Northern Territory. The 13–year period from April 1997 to March 2010 was characterised by severe rainfall deficiencies that covered much of south-western and southeastern Australia and south–eastern Queensland. For many places, the severity and duration of drought were unprecedented, with profound environmental, social and economic implications. Then, in the 12 months from March 2010, large parts of the continent experienced above-average rainfall associated with an extremely strong La Niña event. Most notably, eastern Australia received widespread record–breaking rains, with associated loss of life and massive damage to agriculture, homes and infrastructure.
The summer of 2010–11 will be remembered as one of extremes, with Perth experiencing a record run of temperatures above 30°C. By contrast, when averaged across the continent, summer maximum temperatures were 0.72°C below the norm, making them the lowest since 2001. Despite this, the decade ending in 2010 was the hottest 10–year period on record for Australia, with the average land surface temperature 0.52°C above the 30–year average from 1961 to 1990.
The energy balance of Earth's atmosphere is influenced by the presence of trace levels of GHGs, such as carbon dioxide, methane, nitrous oxide and water vapour (a major GHG), and natural and industrial aerosols. Since the start of the industrial era (around 1750), human activity (principally the burning of fossil fuels) has caused significant increases in the concentrations of these GHGs. Measurements at global background monitoring stations show GHG concentrations continuing to increase in line with long–term trends and future projections. Per person, Australia's GHG emissions are the largest of any OECD country (26.8 tonnes in 2008–nearly twice the OECD average), reflecting Australia's heavy reliance on fossil fuels for our primary energy.
Effectiveness of management
If Australia is to achieve the national 2020 target of a 5% reduction in GHG emissions below 2000 levels, the range and effectiveness of abatement measures will need to be greatly increased. This is the key aim of Securing a Clean Energy Future, the Australian Government's climate change plan released in July 2011, which sets out details of a mechanism to establish a price on carbon and drive reductions in emissions via least–cost means. The plan aims to achieve Australia's unconditional emissions reduction target–a reduction of 5% on 2000 levels by 2020. This will require abatement of at least 23% of GHG emissions by 2020. To achieve Australia's 15% conditional target, a 31% reduction would be needed. The plan builds on existing measures, such as the legislated 20% Renewable Energy Target and the Carbon Farming Initiative, to promote development of renewable energy sources, energy efficiency and action to sequester carbon.
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.
Current governance is complex, because three tiers of government need to work with the private sector and the community to plan for and implement effective mitigation and adaptation measures. Coordination of federal and state programs has improved via actions by the Council of Australian Governments (COAG). Understanding of the science of climate change as it relates to Australia is continuing to improve, as is confidence in modelling projections at both national and regional scales. There is extensive support for policy and priority setting at a national level through the initial Garnaut Climate Change Review (2008) and subsequent review update (2011) and through an improved national GHG emissions reporting system. The Australian Government has established a broad ('three–pillars') strategy, underpinned by the Renewable Energy Target, an energy efficiency strategy and a national adaptation framework that was adopted by COAG in 2007. The Australian Government has committed around $15 billion to climate change initiatives. States and territories are also applying significant resources to mitigation and adaptation programs.
The latest State of the climate report notes that, by 2070, if growth in global emissions of 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 parts per million (with a likely rise of 2°C in global average temperature) or 550 parts per million (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'.
For Australia, with a climate characterised by high variability, climate change poses a clear and present threat. Although projections of Australia's future climate at national and regional scales are still uncertain, the most recent comprehensive review of modelling outcomes shows that a continuing, spatially variable rise in temperatures across the continent is highly likely. Projections of rainfall are more variable, but half of the 23 models considered by the Commonwealth Scientific and Industrial Research Organisation (CSIRO) and the Bureau of Meteorology show an increase in annual and summer rainfall in northern Australia, while nearly all show a decrease in winter rainfall in the south–west and along the south coast. A further risk associated with climate change is the likelihood of more frequent and more severe extreme weather events, such as floods, droughts and heatwaves. These primary atmospheric risks in turn generate a broad series of secondary and tertiary risks, including increased mortality and morbidity due to heatwaves and spread of disease vectors; reduced stream flows and groundwater recharge; reduced soil moisture and loss of topsoil; and changes in habitat with attendant risk to biodiversity. An increase in bushfires is also likely.
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. 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'.
State and trends
Depletion of the stratospheric ozone layer, particularly in the form of the seasonal 'ozone hole' over Antarctica, remains of concern because the ozone layer limits the amount of harmful ultraviolet light reaching the lower layers of the atmosphere. Since peaking in the mid–1990s, levels of stratospheric chlorine and bromine from chlorofluorocarbons and other ODSs have decreased and are continuing to decrease. This drop is expected to continue with the ongoing phase–out of ODSs under the Montreal Protocol on Substances that Deplete the Ozone Layer.
Ambient air quality in Australia's major urban centres is generally good. National health–based standards are rarely exceeded for prolonged periods, and very high levels of pollution are usually associated with short-lived extreme events, such as bushfires and dust storms, that generate very high levels of particulate pollution. Levels of carbon monoxide, nitrogen dioxide, sulfur dioxide and lead have declined in urban areas over the past two decades.
However, air quality in our major cities still impacts on human health. Levels of particles and of the secondary pollutant, ozone, have not decreased. Both these pollutants affect cardiovascular and respiratory health and can lead to illness and death. Research into the health effects of particles and ozone, as well as pollutants such as sulfur dioxide, indicates that there is no threshold level below which they have no health effect. This means that sensitive individuals– such as asthmatics and people with respiratory or cardiovascular disease–may be affected even when air quality standards are met.
Most Australians spend more than 90% of their time indoors, leading to concern over the possible impacts of indoor air quality on our health. Symptoms associated with poor indoor air quality can range from mild and generally nonspecific (eye, nose and throat irritation, and headaches and dizziness) to severe (asthma, allergic responses and increased cancer risk). Despite the potentially significant health effects of indoor air, data on indoor air quality in Australia are limited, and Australia has no specific guidelines for indoor air quality to inform assessments of overall status and trend.
GHGs (notably carbon dioxide, methane and nitrous oxide) that are not controlled under the Montreal Protocol are expected to significantly affect future stratospheric ozone levels. Nitrous oxide is produced by a variety of natural and human-related sources (notably agricultural processes). Although its ozone depleting potential is low relative to chlorofluorocarbon–11, human emissions are at such a large scale that it is recognised as the single most important form of ozone depleting emission, and is expected to remain so throughout this century. Emissions of nitrous oxide could (in the absence of effective abatement strategies) slow the rate of recovery of stratospheric ozone levels.
The air quality in Australia's major cities is no longer principally influenced by emissions from industrial point sources. With the exception of a few centres dominated by large industrial facilities (such as Mount Isa and Port Pirie), widely spread, diffuse emissions now constitute the major source of pollutants in urban areas. Among these, motor vehicles are the single most important source, contributing carbon monoxide, particles, various toxic volatile organic compounds (VOCs) and nitrogen oxides (which, together with VOCs, act as precursors to the formation of ozone). In addition, diesel vehicles are an important source of particles.
Commercial premises are another important diffuse source of pollutants (VOCs and particles). In urban centres where wood heaters are widely used, domestic premises are an important diffuse source of particulate pollution during winter. Planned burning for agriculture, forestry operations and land management can also be a source of diffuse pollution. If not well planned, timed and executed, such burns can trigger health problems and loss of amenity in surrounding areas.
The quality of indoor air is affected by many factors, including building materials (volatile materials like glues and paints), ventilation, furnishings, use of appliances (cooktops, ovens and unflued gas appliances), environmental tobacco smoke and cleaning agents. Rising domestic heating and cooling costs are likely to promote better sealing of dwellings to reduce loss of heated and cooled air. This can be expected to lead to reduced air exchange and a deterioration in indoor air quality.
Effectiveness of management
The Montreal Protocol is one of the world's most effective international environment protection agreements, orchestrating the phase–out of a broad range of ODSs. Australia has ratified the protocol and, as a signatory, all subsequent amendments and has reduced its use of controlled substances well ahead of its international obligations.
For more than a decade, Australia has had national standards and goals for ambient air quality—the National Environment Protection (Ambient Air Quality) Measure (AAQ NEPM)—based on strong empirical evidence about the health impacts of major pollutants. The AAQ NEPM is supported by national emission standards for new vehicles, set in the Australian Design Rules, and by fuel quality standards, both of which are established through Australian Government legislation. Although the size of the Australian vehicle fleet is continuing to grow (as are the distances travelled), emissions are expected to continue to decline over the next decade as a result of tighter national fuel standards and the mandating of improved emission-control technologies.
During the past 30–40 years, state and territory environment protection agencies have employed a variety of regulatory measures (including works approval, licensing and notices) to control and greatly restrict emissions of air pollutants from industrial and commercial sources. More recently, nonregulatory measures (such as codes of practice, market–based mechanisms and cleaner production incentive schemes) have been increasingly used to complement regulatory controls.
Australian governments have also actively sought to improve indoor air quality through a range of interventions (both regulatory and nonregulatory) targeting environmental tobacco smoke and unflued gas heaters. All states and territories prohibit smoking in cinemas and theatres, in most types of public transport and in areas where food is prepared and consumed. Increasingly, similar bans are being applied to various outdoor public spaces. Unflued gas heaters all require compliance with Australian standards. However, as various studies have shown, conformity with the Australian standards does not guarantee that emissions will not adversely affect health.
As a result of the success of the Montreal Protocol in controlling ODSs, the stratospheric ozone layer is expect to recover to 1980 benchmark levels by around mid–century.
The outlook for Australia's urban air quality is generally good. However, there is clear evidence that periods of poor urban air quality have serious adverse impacts on human health. Although levels of carbon monoxide, lead, nitrogen dioxide and sulfur dioxide have decreased over the past 10 years, ozone and particle levels have not declined, and ongoing effort will be required to secure past gains and achieve further improvements. Prospects for reducing levels of ozone and particles will be influenced by a number of factors, most notably vehicle technology, the extent of ongoing urban sprawl, the availability of reliable public transport and the impact of climate change.
Climate change is likely to affect air quality in a variety of ways. Rising temperatures are likely to lead to the formation of more ground-level ozone by increasing the generation of both natural and humangenerated VOCs. Hotter, drier conditions in many parts of the country, together with more extreme weather events (another likely result of climate change) can be expected to increase bushfires and dust storms, leading to short–lived, very high levels of particulate pollution.