Concentrations of atmospheric greenhouse gases
Concentrations of three greenhouse gases (carbon dioxide, methane, and nitrous oxide) in the atmosphere over New Zealand are measured at Baring Head, to the southeast of Wellington. The measurements at Baring Head are representative of atmospheric gases over a wide region of the ocean to the south of New Zealand.
The concentration of all three gases has increased in the past 35 years (see Figure 8.3). The trends in greenhouse gas concentrations observed at Baring Head are consistent with global trends in atmospheric greenhouse gas concentrations (Intergovernmental Panel on Climate Change, 2007a). It is the global atmospheric concentration of greenhouse gases that determines the risk of climate change.
Carbon dioxide concentrations measured at Baring Head have risen from 324 parts per million (ppm) in 1970, to 379 ppm in 2006. The 35-year record measured at Baring Head has an average growth rate of 1.5 ppm each year. The average growth rate of carbon dioxide concentration in the past 10 years of 1.9 ppm is greater than at any other time over the instrumental record starting in 1960. This trend is supported by global observations.
Methane concentrations at Baring Head show an annual growth rate from 1989 to 1997 of 6.5 parts per billion (ppb) each year (see Figure 8.3). Since 1998, there has been a small decrease in methane concentrations in recent years. This pattern is reflected in measurements taken at Arrival Heights, Antarctica, and other global sites. We do not fully understand what drives these changes in methane concentrations.
The observations for nitrous oxide at Baring Head indicate a steady growth trend (see Figure 8.3). Seasonal variation is very small compared with the annual growth rate, because of the long atmospheric lifetime of nitrous oxide. The average annual growth rate is 0.9 ppb each year.
Greenhouse gas emissions and removals
New Zealand’s greenhouse gas emissions represent much less than 1 per cent of total global emissions (Organisation for Economic Co-operation and Development, 2007). While our total emissions are small in the global context, New Zealand ranks 12th in the world for emissions per head of population. For comparison purposes, Figure 8.4 shows carbon dioxide emissions on a population basis for key countries.
National information on greenhouse gas emissions is compiled annually. The data is reported two years in arrears according to international obligations, allowing time for collection, analysis, and reporting. This means that the most recent compiled data for New Zealand is for 2005.
As Figure 8.5 shows, New Zealand has an unusual greenhouse gas emission profile for a developed nation: methane and nitrous oxide from our agricultural sector account for close to 50 per cent of our total emissions. Most of the remainder (43 per cent) is carbon dioxide from energy generation and transport. Many other developed nations have comparatively lower agricultural emissions, and higher emissions from energy generation.
Global warming potentials and CO2 equivalents
Each greenhouse gas has a different warming potential (the relative warming effect of the gas when compared with carbon dioxide). For example, methane has 21 times the global warming potential of carbon dioxide. For ease of comparison, volumes of greenhouse gas emissions and removals are reported in terms of carbon dioxide equivalents (CO2-e) based on 100-year global warming potentials.
Figure 8.6 tracks emissions of carbon dioxide, methane, nitrous oxide, sulphur hexafluoride (SF6), and perfluorocarbons (PFCs) in New Zealand between 1990 and 2005. It shows that emissions of carbon dioxide, methane, and nitrous oxide increased between 1990 and 2005. The increase between 1990 and 2005 for carbon dioxide emissions is 41 per cent.
Total emissions of greenhouse gases in New Zealand for 2005 were 77.2 million tonnes of carbon dioxide equivalents (Mt CO2-e). Figure 8.7 shows that the total emissions in 2005 were 25 per cent higher (15.3 Mt CO2-e) than they were in 1990 (61.9 Mt CO2-e).
Greenhouse gases are removed from the atmosphere by forests, because the trees absorb carbon dioxide as they grow – these are termed ‘forest sinks’ or ‘carbon sinks’.
Planted forests removed a total of 24.5 Mt CO2-e from the atmosphere in 2005, equivalent to 32 per cent of New Zealand’s total greenhouse emissions in that year. This represents an increase in ‘removals’ of 29 per cent since 1990.
Summary of greenhouse gases by sector
Figure 8.8 shows a summary of New Zealand’s greenhouse gas emissions by sector.
In 2005, agriculture made up 49 per cent of our total emissions, energy 43 per cent, industrial processes 6 per cent, and waste 2 per cent.
Emissions from the energy sector
The energy sector covers emissions from fuel combustion (including combustion that produces heat in industrial processes), as well as fugitive emissions (emissions that escape from activities relating to fossil fuels). This category includes emissions from the transport sector.
The energy sector produced 33.4 Mt CO2-e, or 43 per cent of total New Zealand emissions in 2005 (see Figure 8.9). Its rate of emissions growth was the highest of any sector in New Zealand between 1990 and 2005. Emissions increased by 9.9 Mt CO2-e, or 42 per cent over the period.
Transport emissions include those from domestic road, rail, air, and sea transport. In line with international reporting guidelines, international air transport and shipping are not included in these emissions totals.
In 2005, transport contributed 14.2 Mt CO2-e or 18 per cent of New Zealand’s total emissions. Emissions were 62 per cent higher in 2005 than in 1990 (8.8 Mt CO2-e).
Road transport represented 89 per cent (12.6 Mt CO2-e) of domestic transport emissions in 2005. Domestic aviation contributed a further 7 per cent (1.0 Mt CO2-e), shipping 3 per cent (0.4 Mt CO2-e), and rail 1 per cent (0.2 Mt CO2-e). The largest growth in transport emissions is associated with road transport. Emissions from road transport increased by 65 per cent (5.0 MtCO2-e) between 1990 and 2005.
The energy industries category comprises stationary energy supplies. These include electricity generation, petroleum refining, gas processing, and solid fuel manufacturing. Emissions from energy industries were 9.3 Mt CO2-e in 2005 or 12 per cent of national emissions. Energy industries emissions increased by 54 per cent between 1990 and 2005. This increase is primarily due to growth in electricity demand in New Zealand. Growing demand has required more burning of gas, coal, and oil to produce energy. (See chapter 5, ‘Energy’.)
Electricity generation and heat production comprised 88 per cent (8.2 Mt CO2-e) of the energy industries subcategory in 2005.
Manufacturing industries and construction
This category includes emissions from the manufacture of steel, non-ferrous metals, and pulp and paper, and emissions from food processing. Emissions from manufacturing industries and construction contributed 6 per cent (4.9 Mt CO2-e) to New Zealand’s total greenhouse gas emissions in 2005. This represents a 6 per cent increase from 1990 levels.
Other fuel combustion
This category includes emissions from commercial, public, and residential sectors. It covers fuel used by agricultural, fishery, and forestry equipment, and all other fuel combustion emissions. Emissions were 3.4 Mt CO2-e, or 4 per cent of national greenhouse gas emissions in 2005. This was a 17 per cent increase on emissions reported in 1990.
Emissions from the industrial processes and solvents sectors
The industrial processes and solvents sectors produce only a small proportion of New Zealand’s total greenhouse gas emissions.
Industrial processes sector
Emissions from industrial processes include the chemical transformation of one product to another, for example, the reduction of ironsand in steel production. (Emissions from energy used to produce heat in the process are reported within the energy sector.)
The main industrial processes producing greenhouse gases in New Zealand are:
reduction of ironsand in steel production
oxidisation of anodes in aluminium production
production of hydrogen
calcination of limestone for use in cement production
calcination of limestone for lime
production of ammonia and urea.
Most greenhouse gas emissions in this sector are in the form of carbon dioxide. Small contributions come from perfluorocarbons and sulphur hexafluoride.
Emissions from industrial processes were 4.4 Mt CO2-e in 2005 (see Figure 8.10) and represent 6 per cent of total national emissions. This emission category has grown by 32 per cent since 1990, mainly due to an increase in emissions from metal production and consumption of perfluorocarbons.
Most emissions in the solvents sector are indirect emissions, which are reported but do not get counted with New Zealand’s total emissions. Indirect emissions are from evaporation of volatile chemicals when solvent-based products are exposed to air. This occurs during processes such as chemical cleaning, dry cleaning, printing, metal degreasing, and from a variety of industrial and household chemical uses. Emissions from paints, lacquers, thinners, and related materials are also included.
The category, which includes solvents and other product use, is a minor contributor to New Zealand’s total greenhouse gas emissions, being responsible for just 0.05 Mt CO2-e. Emissions have increased by 16 per cent since 1990.
Emissions from the agricultural sector
New Zealand has a unique emissions profile with 49 per cent (37.4 Mt CO2-e) of emissions in 2005 produced by the agricultural sector (see Figure 8.11). Typically, emissions from agriculture for other developed countries make up around 12 per cent of total emissions. Agriculture contributes 96 per cent of New Zealand’s total nitrous oxide emissions and 91 per cent of total methane emissions. Emissions have increased by 15 per cent from 1990 levels (32.5 Mt CO2-e).
Emissions of methane and nitrous oxide are produced when biomass (organic matter) is consumed or decays. Naturally occurring emissions are modified by human activities such as cultivation, addition of nitrogenous fertilisers, farming of livestock, and deliberate burning.
Enteric fermentation is a digestion process in ruminant livestock. The process produces methane. This is New Zealand’s highest single emissions category, contributing 23.9 Mt CO2-e, or 31 per cent to total national emissions in 2005. Enteric fermentation represents 64 per cent of all emissions from agriculture. Emissions have increased by 10 per cent since 1990.
Nitrous oxide emissions in this category are associated with the application of nitrogenous fertilisers, animal effluent deposited on agricultural soils, and the use of nitrogen-fixing crops. Emissions can be direct from the soil, and indirect through atmospheric deposition, leaching, and run-off. Agricultural soils contributed 34 per cent of all agricultural emissions primarily as nitrous oxide (12.7 Mt CO2-e) in 2005. Emissions were 27 per cent higher than in 1990.
This category produces nitrous oxide and methane emissions from the decomposition of animal waste held in manure management systems (for example, stored in ponds). Emissions were 0.8 Mt CO2-e in 2005.
Grassland burning and burning of agricultural residues
This category includes emissions from the controlled burning of tussock grasslands. The amount of tussock burned has been steadily decreasing since 1959. Emissions from this category comprised 0.001 Mt CO2-e in 2005.
Emissions are also produced from field burning of crop residues (from barley, wheat, and oats). Emissions were 0.014 Mt CO2-e in 2005.
Emissions from the waste sector
Greenhouse gas emissions from waste are predominantly methane, formed from organic wastes (such as food) as they break down over time. Small amounts of nitrous oxide are also generated from the incineration of solvents and decomposition of human waste.
Carbon dioxide emissions from the breakdown of organic material derived from plant materials are not reported because the carbon dioxide emitted is assumed to be reabsorbed in crops in the following year.
Waste emissions were 1.9 Mt CO2-e in 2005, a decrease of 26 per cent since 1990 (see Figure 8.12). This decrease is because of improved capturing of landfill gas from solid waste disposal. The waste sector contributed 2 per cent to New Zealand’s total greenhouse gas emissions in 2005.
Solid waste disposal on land represented 79 per cent (1.5 Mt CO2-e) of waste sector greenhouse gas emissions in 2005. The remainder (21 per cent) is associated with wastewater handling. Wastewater emissions are largely associated with sewage from New Zealand’s human population.
Climate change legislation
Climate Change Response Act 2002
The Climate Change Response Act 2002 put in place a legal framework to allow New Zealand to ratify the Kyoto Protocol and to meet its obligations under the United Nations Framework Convention on Climate Change and Kyoto Protocol. The Act will enable New Zealand to trade emissions units (carbon credits) on the international market, and establishes a registry to record holdings and transfers of units. The Act also establishes a national inventory agency to record and report information relating to greenhouse gas emissions in accordance with international requirements.
Resource Management Act 1991 and climate change
Under the Resource Management (Energy and Climate Change) Amendment Act 2004 the Resource Management Act 1991 was amended to:
( a) make explicit provision for all persons exercising functions and powers under the principal Act to have particular regard to—
(i) the efficiency of the end use of energy; and
(ii) the effects of climate change; and
(iii) the benefits to be derived from the use and development of renewable energy; and
(b) to require local authorities—
(i) to plan for the effects of climate change; but
(ii) not to consider the effects on climate change of discharges into air of greenhouse gases.
The Resource Management (Energy and Climate Change) Amendment Act 2004 confirmed the Government’s policy that emissions of greenhouse gases be controlled at a national level. The Act removed the power of local government to consider the effect of greenhouse gas emissions on climate change when making rules in regional plans, or when determining air discharge consents, except where necessary to implement a national environmental standard.
One national environmental standard for air quality relates to greenhouse gas emissions. It requires that all operating landfills with a capacity of over 1 million tonnes of refuse collect and either destroy or utilise greenhouse gas emissions (methane).
Under the Resource Management Act 1991, there remains some power for regional councils to control emissions, but not for climate change purposes.
Emissions and removals from the land use, land-use change, and forestry sector
Changes in the amount of carbon in vegetation and soil as a result of human activity are reported in the land use, land-use change, and forestry (LULUCF) sector. This includes removals of greenhouse gases from the atmosphere by forest sinks, as well as emissions from changes in land use.
Forests remove carbon dioxide from the atmosphere and store it as carbon.
Source: Courtesy of Peter Wiles, Ngahere Muri Forestry Limited.
The category includes changes in six land-use types: forest land, cropland, grassland, wetlands, settlements, and other land. Transfers of land use from one type to another can result in either carbon dioxide emissions or removals. In addition, even where land use stays the same, changes in carbon emissions or removals can occur. An example is where planted forest growth removes carbon dioxide from the atmosphere and stores it as carbon. Emissions can also arise from burning of forest slash (branches and other woody debris from forest harvesting that are not removed from the site), decay of biomass, and changes in soil carbon.
In New Zealand, on balance, this sector represents a carbon sink; that is, there are more removals in this sector than emissions. As noted earlier, removals of greenhouse gas emissions in 2005 equated to 24.5 Mt CO2-e (see Figure 8.13). This removal is equivalent to 32 per cent of our total greenhouse gas emissions. Overall, total LULUCF removals have increased in New Zealand by 29 per cent between 1990 and 2005.
The trends observed in this sector primarily reflect New Zealand’s changing land-use and forestry activities, particularly during the 1990s with the high forestry planting rates (see chapter 9, ‘Land’, for details on forestry planting and deforestation). In 2005, removals of greenhouse gases from forestry represented the majority of removals in the sector. Removals of greenhouse gases from other changes in land use were not significant.
Local action on climate change
Communities for Climate Protection – New Zealand
Communities for Climate Protection – New Zealand (CCP–NZ) is a voluntary programme that helps local government reduce greenhouse gas emissions from council operations and their wider communities. CCP–NZ provides a framework for taking action to reduce greenhouse gas emissions through energy conservation, renewable energy, sustainable transport, waste reduction, improved building and urban design, and emission-reduction technologies.
Bay of Plenty adaption to climate change
In May 2005, the Western Bay of Plenty was hit by an intense storm that caused flooding throughout the region. A state of emergency was declared, because stormwater infrastructure, roading, and private properties were substantially damaged by the flooding.
While average annual rainfall in the Bay of Plenty is expected to decrease with climate change, extreme rainfall events and flooding such as that which occurred in May 2005 are projected to increase. This has significant implications for new subdivisions and development in the area.
In response, the Tauranga City Council now considers climate change impacts when designing all new or upgraded stormwater infrastructure. The Council has also incorporated the factor of increased high-intensity rainfall into its planning for growth and development in the region over the next 50 years.
Tauranga City Council has upgraded the city's stormwater infrastructure.
Source: Courtesy of Tauranga City Council.
Impacts of sea level rise on the Avon River, Christchurch
In 2003, Christchurch City Council examined the potential effects of climate change on the Avon catchment and associated coastal areas, and how these risks could be managed.
The study focused primarily on an economic analysis of likely damages, and the response options available to local government to mitigate these. Possible responses the study discussed included minimum floor levels for buildings, subdivision restrictions, stopbank improvements, and tidal barrages.
Since this study was undertaken, changes have been made to the city plan and aspects of the study’s findings have been incorporated into the Urban Development Strategy that seeks to reduce the risks to the community from climate change. Options such as set-backs from waterways and raised floor levels of buildings in flood-prone areas have been incorporated.
Wellington City Council and CLINZI
Wellington City Council has undertaken a CLINZI (Climate's Long-term Impact on New Zealand's Infrastructure) study that asked, ‘What is the impact of climate change on infrastructure systems and services in Wellington City?’
CLINZI is an integrated assessment process for assessing the long-term impact of climate on infrastructure investments. It has been developed by the New Zealand Centre for Ecological Economics in conjunction with the National Institute of Water and Atmospheric Research and the International Global Change Institute, and involves the generation of local climate scenarios, regression modelling, and qualitative analysis, all within a risk-management framework.
The risk analysis work identified several areas requiring further attention by Wellington City Council, including:
change in water demand
possible reduction in water quality
effect of sea-level rise on stormwater discharge rates to the sea
changes in electricity demand
impacts on transmission assets
impacts of erosion and extreme rainfall events on maintenance of roads
changes in traffic demand.
The analysis of policies and strategies concluded that, while Wellington acknowledged potential climate-change risk in a range of official documents such as the Regional Policy Statement, further work is needed on incorporating climate change impacts in other policies and plans.
Incorporating climate change adaptation into the state highway network
As the Crown Entity responsible for state highways, Transit New Zealand is required to assess and manage risks to New Zealand’s transport network, and ensure its sustainability.
Transit New Zealand recognises that it is prudent to consider climate change in the design and planning of all major long-life infrastructures such as bridges, culverts, and causeways that could be affected by climate change impacts within the working life of the structure.
Future-proofing at the design stage makes later retrofits both feasible and cost-effective. Some new state highway projects are already considering the impacts of climate change during design and construction. For example, the new section of causeway for Auckland’s Upper Harbour Corridor (State Highway 18) was built 0.3 metres higher than the existing causeway, which was then raised to match it. This was in direct response to predicted sea-level rise.
Stratospheric ozone levels
Stratospheric ozone levels in New Zealand have changed considerably over time, as shown in Figure 8.14. Levels have stabilised in the last decade, reversing decreases in the 1980s and 1990s. A turning point in ozone concentrations may have been reached in 1997. Much of the stabilisation over the last decade can be attributed to reduced ozone depletion over Antarctica as a result of higher springtime polar temperatures and slightly reduced levels of chlorine and bromine in the stratosphere.
The average ozone concentration in 2006 was 298 DU (Dobson units), one of the five lowest levels on record (National Institute of Water and Atmospheric Research, pers comm). The 2006 level can be explained by unusual stratospheric weather in that year (Bodeker et al, 2007).
Levels of ozone-depleting substances in the atmosphere
As discussed earlier, atmospheric concentrations of chlorine and bromine drive ozone depletion. Figure 8.15 shows the changing concentration of atmospheric chlorine and bromine expressed as ‘chlorine equivalents’. Levels of these gases are expressed in units of equivalent effective chlorine, in much the same way as greenhouse gases are expressed in carbon dioxide equivalents.
Comparison of Figures 8.14 and 8.15 shows that ozone levels track closely to average annual levels of chlorine equivalents, although there is a time lag. Concentrations of atmospheric chlorine and bromine have decreased over New Zealand since 1996 and over Antarctica since 2001 (National Institute of Water and Atmospheric Research, pers comm). This decrease is primarily because of the global adherence by parties to the Montreal Protocol (see box ‘Montreal Protocol’), which established targets for the reduction in the use of ozone-depleting substances.
The Montreal Protocol on Substances that Deplete the Ozone Layer 1987 sets targets for reducing the production and consumption of ozone-depleting substances. The protocol originally required parties to reduce chlorofluorocarbon (CFC) use to 50 per cent below 1986 levels by 1998, and to freeze halon consumption at 1986 levels from 1992.
The provisions of the protocol have since been tightened through a series of amendments. Halons and CFCs were phased out completely by the early to mid-1990s. Phase-out schedules were agreed for other substances as the impact of those substances on ozone layer depletion became better understood.
New Zealand’s obligations under the Montreal Protocol are implemented through the Ozone Layer Protection Act 1996 and the Ozone Layer Protection Regulations 1996.
Ozone depletion reduces the protective properties of the atmosphere and allows higher levels of UV radiation to reach the earth’s surface. Figure 8.16 tracks summertime UV index levels over New Zealand against ozone concentrations. This comparison shows the impact of ozone levels on UV: when ozone levels are low, we experience a high UV index.