Atmosphere Theme Report

Australia State of the Environment Report 2001 (Theme Report)
Lead Author: Dr Peter Manins, Environmental Consulting and Research Unit, CSIRO Atmospheric Research, Authors
Published by CSIRO on behalf of the Department of the Environment and Heritage, 2001
ISBN 0 643 06746 9

Climate Variability and Change (continued)

Enhanced greenhouse effect [A Indicator 1.10]

Atmospheric constituents such as carbon dioxide, methane, nitrous oxide and water vapour contribute to a natural greenhouse effect, and, with clouds, maintain the earth's energy balance. The earth's energy balance can change through increasing concentrations of greenhouse gases in the atmosphere, as a result of human activities and natural events.

The first systematic observations of the atmospheric concentration of carbon dioxide commenced in 1958 at Mauna Loa, Hawaii. Since then several atmospheric concentration observation sites have been established and, at present, there are about 140 stations measuring carbon dioxide, and methane, but fewer measure nitrous oxide. Measurements from these stations help us to understand spatial variations of these gases although at many stations, established at different times and for different purposes, they are not continuous.

Figures 51, 52 and 53 show the variations in the atmospheric concentration of carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O) since AD 1000, based on composites of ice core data from Antarctica and (in recent years) from direct measurements at the Cape Grim Baseline Air Pollution station, Australia. A strong seasonal variation in carbon dioxide is superimposed on an overall upward trend in Figure 54.

Figure 51: Carbon dioxide concentration from ice core and air samples since AD 1000

Web unit request

Source: CSIRO Atmospheric Research

Figure 52: Methane concentration from ice core and air samples since AD 1000

 Methane concentration from ice core and air samples since AD 1000

Source: CSIRO Atmospheric Research

Figure 53: Nitrous oxide concentrations since AD 1000 from ice cores and direct atmospheric sampling

 Nitrous oxide concentrations since AD 1000 from ice cores and direct atmospheric sampling

Source: CSIRO Atmospheric Research

Figure 54: Carbon dioxide concentrations and growth rate at Cape Grim since 1976.
Solid line depicts actual values of carbon dioxide and dotted line shows the growth rate.

 Carbon dioxide concentrations and growth rate at Cape Grim since 1976

Source: CSIRO Atmospheric Research and Cape Grim Baseline Air Pollution Station

Tasmania's Cape Grim Baseline Air Pollution Station is an integral component of the global network station, representing the conditions over much of the Southern Hemisphere. It provides extensive information about the seasonal to interannual variability and growth rates of greenhouse gases carbon dioxide, methane and nitrous oxide (Figures 54, 55 and 56). These records have been used extensively to study the changes in the global atmosphere (Steele et al. 1999; Langenfelds et al. 2001). Concentrations of these greenhouse gases have increased since measurements began. Growth rates in carbon dioxide vary between 1 and 3 ppm per year. The growth rate in methane was less during the 1990s than in the previous decade. Nitrous oxide has a slower growth rate compared with the growth rate of carbon dioxide.

Figure 55: Methane concentrations and growth rate at Cape Grim since 1984
Solid line depicts actual values of methane and dotted line shows the growth rate.

 Methane concentrations and growth rate at Cape Grim since 1984

Source: CSIRO Atmospheric Research and Cape Grim Baseline Air Pollution Station

Figure 56: Nitrous oxide concentrations and growth rate at Cape Grim since 1993.
Solid line depicts actual values of nitrous oxide and dotted line shows the growth rate.

 Nitrous oxide concentrations and growth rate at Cape Grim since 1993

Source: CSIRO Atmospheric Research and Cape Grim Baseline Air Pollution Station

Australia has very high emissions of carbon dioxide in terms of per capita and per unit of GDP (Figures 57 and 58). A comparison between Australia and other selected countries indicates that carbon dioxide emissions per capita have been gradually increasing in Australia, while emissions per unit of GDP shows a slow decrease during the last two decades. Records (IEA 1998) indicate that carbon dioxide emissions per capita for Australia between 1990 and 1996 increased by 7.5% and carbon dioxide emission per unit of GDP decreased by 3.5%. However, records based on the analysis from 1990 to 1998 (AGO 2000a) show an increase of 6.5% in carbon dioxide emissions per capita in Australia and a decrease of carbon dioxide emission per unit of GDP by 8.2% during this period.

Figure 57: Carbon dioxide emissions per capita for selected countries.
Percentage changes between 1990 and 1996 are shown as hexagons, which are related to the right-side scale.

 Carbon dioxide emissions per capita for selected countries

Source: IEA (1998)

Figure 58: Carbon dioxide emissions per unit of gross domestic product (GDP) for selected countries.
Values are based on US$ in 1990 and exchange rates. Percentage changes between 1990 and 1996 are shown as hexagons, which are related to the right side scale.

 Carbon dioxide emissions per unit of gross domestic product (GDP) for selected countries

Source: IEA (1998)

Australia's total carbon dioxide emissions are relatively small compared with other OECD countries (Figure 59). The rate of growth in these emissions in Australia has increased substantially due to increases in population, industrialisation and electrification. Most of Australia's carbon dioxide emissions are from electricity generation, and heat production and from transport, with manufacturing industries and construction contributing smaller amounts.

Figure 59: Carbon dioxide emissions by subsectors from selected countries in 1996

 Carbon dioxide emissions by subsectors from selected countries in 1996

Source: IEA (1998)

Commonwealth and state governments and some local councils have taken measures to respond to global warming by reducing greenhouse gases. The National Greenhouse Strategy, which was endorsed by all states and territories and the Commonwealth in 1998, extended the 1992 program of actions (i.e. the National Greenhouse Response Strategy). The National Greenhouse Strategy has eight modules that aim to reduce greenhouse gas emissions, enhance greenhouse sinks and increase understanding of the effect of greenhouse gases. Measures include planting trees and land use management to enhance greenhouse sinks, introducing efficient energy use methods, development of renewable energy and integrated transport system that save energy and reduce emissions from motor vehicles. Since greenhouse gas concentrations influence temperature as well as the entire climate system, this Report presents the latest climate change scenarios for temperature and rainfall changes for Australia derived from a range of simulation models of global climate.