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Topic 3: Air and atmosphere

The atmosphere enveloping the Earth is a vital part of the world we live in. It contains the oxygen we need to breathe, protects us from extreme temperatures and dangerous levels of ultraviolet radiation, and plays an essential role in recycling energy, water, and other essentials for life, such as nitrogen. Weather, an important influence on our pattern of living, is a direct product of atmospheric processes.

There is convincing evidence that as a result of industrial and other human activities gases are being emitted into the atmosphere in such quantities that the composition and dynamics of the atmosphere are changing. The changes occurring in the atmosphere are likely to have significant environmental, social, health, and economic effects.

In recent decades, global attention has focused on two environmental issues in relation to the atmosphere: climate change and depletion of ozone. This topic discusses the New Zealand aspects of these environmental issues and also looks at the quality of air in our major centres of population.

Main results

New Zealand’s net greenhouse gas emissions have increased since 1990, with most emissions being from the agriculture and energy sectors. However, the intensity of emissions in relation to economic activity has decreased.

Ozone levels over New Zealand have begun to recover, increasing over the 10 years to 2008. Over the same time period, air quality at selected sites within the main centres of population has fluctuated.

Table 3.1
Air and atmosphere indicators – key results

 Air and atmosphere indicators – key results.

What the indicators tell us

Net greenhouse gas emissions (indicator 3.1)

This indicator measures net annual emissions of greenhouse gases. This is emissions created as a result of human activity minus emissions removed, primarily by forests.

Net greenhouse gas emissions increased by 18 percent between 1990 and 2007, but have remained steady since 2002.

Total greenhouse gas emissions in New Zealand increased 22 percent between 1990 and 2007. New Zealand’s emissions represent much less than 1 percent of the global total. While our total emissions are small in the global context, New Zealand ranked 11th in the world in 2005 for greenhouse gas emissions per person (World Resources Institute, 2009).

Trees absorb carbon dioxide (CO2) as they grow, and thereby remove it from the atmosphere. A total of 23.8 million tonnes of CO2 equivalents were removed from the atmosphere in 2007, equivalent to 32 percent of New Zealand’s total greenhouse gas emissions in that year. This represents a 31 percent increase in ‘removals’ since 1990.

Figure 3a shows net emissions, as well as data for total emissions and removals. This provides a fuller picture of the situation, which is not conveyed by net emissions alone. For example, net emissions are likely to increase as a result of a decrease in removals when the large quantity of forests planted in the early 1990s mature or are harvested.

Greenhouse gas emissions and removals, 1990–2007.

Greenhouse gas emissions by sector (indicator 3.2)

New Zealand has an unusual profile of greenhouse gas emissions for a developed nation, due to the high proportion coming from the agricultural sector. This sector is the largest source of emissions, contributing 48 percent of the total in 2007. Agricultural emissions consist of methane (emitted by livestock) and nitrous oxide (by-product of animal excrement and nitrogen fertilisers in soils). The energy sector (including the transport sector) contributed 43 percent of total emissions. The remaining emissions are from industrial processes, solvents, and waste.

Agricultural emissions have increased 12 percent from 1990 levels. This has largely been driven by increases in methane and nitrous oxide emissions from increasing numbers of dairy cattle. However, the biggest increase in emissions is from the energy sector, up 39 percent from 1990 levels (see indicator 6.6). This growth is primarily from growth in emissions from transport. Emissions for the waste sector have decreased 25 percent as a result of initiatives to improve solid waste management practices (see figure 3b).

Comparison of greenhouse gas emissions by sector, 1990 and 2007 December years.

Annual surface temperature (indicator 3.3)

Climate change is likely to bring about rising sea levels, an increase in floods and droughts, changing wind and rainfall patterns, increasing temperatures, fewer frosts, increased pressure on ecosystems, and an increase in the threat of pest species becoming established here (Ministry for the Environment, 2007a).

Figure 3c shows the difference in average temperature of individual years in New Zealand, compared with an average for the period 1971 to 2000. Over the last century, from 1908 to 2008, New Zealand’s average surface temperature increased 0.9°C. This is shown by the straight line in figure 3c, which represents long-term movement in the data. This is consistent with the increase of 0.76°C in average global surface temperature over the past century (Intergovernmental Panel on Climate Change, 2007).

New Zealand's average surface temperature, 1908–2008.

Greenhouse gas intensity of the economy (indicator 3.4)

Greenhouse gas emissions can be reduced through improvements in efficiency. The ratio (intensity) of total greenhouse gas emissions to GDP, which takes into account production and consumption levels, has fallen since 1990. Figure 3d shows that since the early 1990s, GDP has increased at a greater rate than total greenhouse gas emissions. This means fewer emissions are produced per unit of GDP.

The downward trend in the intensity of greenhouse gases produced could suggest that resources are being used more efficiently. Possible reasons include structural factors arising from changes in the composition of the economy. These include the growth of the service sector, which produces less greenhouse gases comparative to other industries, and the relatively slower growth of the electricity, gas, and water industries, which are more emissions intensive. Three-quarters of economic growth, over the period 1990 to 2007, was generated by the service industries. In contrast, the electricity, gas, and water industry group, grew by only 20 percent over the same period, compared with total GDP that increased by 64 percent. (See also indicator 6.2, which shows that the energy intensity of the economy has been decreasing.)

Intensity of greenhouse gas emissions, 1990–2007.

Stratospheric ozone levels (indicator 3.5)

Most atmospheric ozone is in the stratosphere, 10–50km above Earth’s surface. This ozone layer shields Earth from the sun’s ultraviolet radiation, which can cause skin cancer, speed the degradation of materials, damage the marine environment, and distort plant growth.

This indicator measures concentrations of stratospheric ozone over New Zealand.

Although yearly average ozone levels over New Zealand have fluctuated, the overall trend is that ozone levels decreased between 1970 and 1996, but recorded a small increase over the decade to 2008 (see figure 3e). This is in line with slightly reduced levels of ozone depleting substances in the stratosphere.

Ozone depletion is an international issue that particularly affects New Zealand because of our proximity to Antarctica. Decreases in ozone depleting substances over New Zealand and Antarctica are primarily a result of actions following the 1987 Montreal Protocol on Substances that Deplete the Ozone Layer (United Nations Environment Programme, 1987).

Ozone levels over New Zealand, 1970–2008.

Air pollution (indicator 3.6)

Sustainable development requires that human health is protected and promoted. Clean air for people to breathe is a basic condition for this requirement.

Air quality in New Zealand is within acceptable limits in most places, most of the time. PM10 (a collective term for very small particles, such as dust, smoke, or fog) is an air pollutant of particular concern because it regularly occurs at high levels in urban areas and is linked to harmful health effects. As these small particles are easily inhaled and absorbed into the lungs, PM10 can cause significant health problems such as heart disease and respiratory diseases, particularly for older people, infants, and those with asthma. PM10 is caused mainly by burning solid fuels for home heating and from exhaust emissions from vehicles.

Two methods of reporting PM10 are included here: annual average concentrations of PM10 and the number of days PM10 exceeds acceptable levels. Annual average concentrations of PM10 provide a long-term picture of air quality and are reported against the national air quality guideline (see figure 3f). The number of days PM10 concentrations exceed acceptable levels (see figure 3g) indicates the intensity of air pollution and extent of associated health risks to which people are exposed. This is reported against a national minimum standard that outdoor quality should meet in order to protect human health.

The annual averages of PM10 at monitored sites in Auckland, Hamilton, Wellington, Christchurch, and Dunedin have fluctuated over the 10 years to 2007. Weather is one reason for this fluctuation because it is an important influence on air quality. The only main centre to show a clear decreasing trend is Christchurch.

PM<sub>10</sub> concentrations in main centres of population, annual average.

Figure 3g shows the number of times the 10 sites with the highest frequency of exceeding air quality levels in 2007 exceeded the PM10 standard for 2005–07. With the exception of Christchurch, the highest number of days exceeded are in provincial areas, and occur mostly during the winter months.

Number of days air quality exceeded the PM<sub>10</sub> standard, by selected sites.

About the indicators

Net greenhouse gas emissions and greenhouse gas emissions by sector (indicators 3.1, 3.2)

Greenhouse gases include carbon dioxide, methane, nitrous oxide, sulphur hexafluoride, hydrofluorocarbons, and perfluorocarbons. The quantity of greenhouse gases emitted to the atmosphere as a result of human activity in New Zealand is estimated as part of a national greenhouse gas inventory. Methodologies and reporting formats agreed by the parties to the United Nations Framework Convention on Climate Change (UNFCCC) have been used in reporting the New Zealand greenhouse gas inventory (Ministry for the Environment, 2007a).

Greenhouse gas emissions are measured in CO2 equivalents. Each greenhouse gas has a different warming potential (the relative warming effect of the gas when compared with CO2). For example, methane has 21 times the global warming potential of CO2. For ease of comparison, volumes of greenhouse gas emissions and removals are reported in terms of CO2 equivalents, based on 100-year global warming potentials (Ministry for the Environment, 2007a).

Estimates of removals of greenhouse gases from the atmosphere are continuously improved as more information and research is available. The New Zealand Greenhouse Gas Inventory 1990–2007 includes deforestation estimates based on provisional data. Final data available in early 2008 suggests these provisional estimates were low. The final deforestation data for 2007 will be included in the 2010 inventory submission (Ministry for the Environment, 2009).

Under the Kyoto Protocol, CO2 removed by forests planted after 1990 can be counted as ‘sinks’ and deducted from total emissions. However, figure 3a includes removals by forests planted before 1990.

The information is sourced from the New Zealand Greenhouse Gas Inventory 1990–2007 (Ministry for the Environment, 2008). The industry sectors used in this analysis are based on those used in the greenhouse gas inventory. These are different from the Australia and New Zealand Standard Industrial Classification.

Annual surface temperature (indicator 3.3)

The annual temperature measurements since 1908 are from seven long-term stations that represent coastal and lowland locations (Salinger & Mullan, 1999). The National Institute of Water and Atmospheric Research (NIWA) will produce annual temperature anomalies based on stations representing the entire land area of New Zealand at a later date.

Greenhouse gas intensity of the economy (indicator 3.4)

The indicator is total greenhouse gas emissions (see indicator 3.1) divided by GDP in volume terms, expressed in 1995/96 dollars, therefore removing the effect of price changes.

Carbon intensity of the economy (CO2 emissions divided by GDP) is another common measure of the relationship between emissions and the economy. The indicator used in this report includes all greenhouse gas emissions.

Stratospheric ozone levels (indicator 3.5)

This indicator focuses on ozone occurring naturally in the upper atmosphere, or stratosphere, where it screens out harmful ultraviolet radiation. Ozone can also occur at ground level where it is associated with air pollution that affects the respiratory and cardiovascular system and can cause tissue damage to the lungs (Ministry for the Environment, 2007a).

Depletion of the ozone layer is caused primarily by emissions of gases containing chlorine and bromine (primarily chlorofluorocarbons (CFCs) and halons) caused by human activities. Five-year averages have been plotted to give an indication of trends in ozone concentration.

Stratospheric ozone levels for New Zealand are measured by NIWA, over Lauder in Central Otago, as a ‘total column ozone’ – the total amount of ozone in a column of air from the Earth’s surface to the top of the atmosphere. This data illustrates the degree of ozone depletion, or conversely, the rate of ozone layer recovery at mid-latitudes in the southern hemisphere.

Air pollution (indicator 3.6)

PM10 is any solid or liquid particulate matter in the air that is less than 10 microns in diameter.

The data from the Ministry for the Environment, gives annual averages for selected sites rather than the centre as a whole. The respective sites for Auckland, Wellington, and Christchurch are Takapuna, Upper Hutt, and St Albans. Annual averages even out both peak and low pollution periods, and show a long-term picture of air quality.

Figure 3g shows breaches of the daily standards of PM10 for the years ended December 2005–07.

Table 3.2
Air and atmosphere indicators – defining principles

Air and atmosphere indicators - defining principles.

See part C for the complete list of defining principles for all indicators.

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