In recent decades, global attention has focused on two environmental issues in relation to the atmosphere: climate change and depletion of atmospheric ozone. In response, the international community has acted to quantify and reduce emissions of greenhouse gases and ozone-depleting substances.
Greenhouse gases, global warming potentials and CO2 equivalents
The major greenhouse gases include water vapour, carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O). Other greenhouse gases at lower concentrations include sulphur hexafluoride (SF6), perfluorocarbons (PFCs), and hydrofluorocarbons (HFCs).
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’).
Our changing atmosphere
Echoing global trends, atmospheric levels of carbon dioxide over New Zealand increased from 324 to 379 parts per million between 1970 and 2006. Atmospheric nitrous oxide levels showed an average increase of 0.9 parts per billion each year over the last decade. Methane levels have shown a small reduction in recent years.
The changing climate
Average surface temperatures in New Zealand have risen by 0.9°C between 1920 and 2000. As a country reliant on primary production and tourism for its economic wealth, New Zealand stands to be much affected by the impacts of climate change. Historical climate patterns can no longer be taken as an accurate guide to the climate we will experience in the future. Climate change is likely to bring to New Zealand rising sea levels, increased floods and droughts, changes in wind and rainfall patterns, increasing temperatures, fewer frosts, and changes to our ecosystems and pest species.
Emissions and sinks
New Zealand’s greenhouse gas emissions represent much less than 1 per cent of global emissions, but on a per capita basis we are the 12th highest emitter. In 2005, our total greenhouse gas emissions amounted to 77.2 million tonnes of CO2-e. Between 1990 and 2005, our total greenhouse gas emissions increased by 25 per cent, reflecting our growing population and economy.
The largest growth in our emissions since 1990 has been in the energy sector (an increase of 9.9 million tonnes of CO2-e) and agriculture sector (almost 5 million tonnes of CO2-e). This growth has been offset by a concurrent increase in removals to forest sinks (5 million tonnes of CO2-e, or 29 per cent since 1990). The increase in removals to forest sinks is largely due to increases in plantation forestry in the mid-1990s, as discussed further in the Land section.
Forests remove carbon dioxide from the atmosphere and store it as carbon
Source: Courtesy of Peter Wiles, Ngahere Muri Forestry Limited.
New Zealand has an unusual greenhouse gas emissions profile for a developed nation. As Figure 3.2 shows methane and nitrous oxide from the agricultural sector contribute close to 50 per cent of our total emissions. Carbon dioxide emissions, largely from energy generation and transport, contribute most of the other 50 per cent. Many other developed nations have comparatively lower agricultural emissions and higher emissions from energy generation.
(1) Removals indicate the uptake of carbon dioxide by forests.
(2) Mt CO2-e = megatonnes of carbon dioxide equivalents.
Source: Ministry for the Environment, 2007b.
Mt CO2 equivalent
New Zealand and the Kyoto Protocol
The Kyoto Protocol under the United Nations Framework Convention on Climate Change was agreed in 1997 and came into force in 2005. The protocol sets targets for the greenhouse gas emissions of developed countries for the period 2008 to 2012 (the first commitment period). For that period, it aims to reduce the total greenhouse gas emissions of developed countries to 5 per cent below the level they were in 1990.
Different countries have different targets to achieve. New Zealand’s target is to reduce its greenhouse gas emissions to the level they were in 1990, or take responsibility for excess emissions. Negotiations are now under way on further commitments for developed countries under the Kyoto Protocol.
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 enables 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.
Challenges and opportunities
Climate change is a long-term issue that presents both risks and opportunities for New Zealanders. We start from a relatively favoured situation with high levels of renewable electricity generation, and low average population density. Forest cover in New Zealand is extensive, we enjoy a temperate climate, and awareness of environmental issues is well established. But we also face challenges.
Much of our economy is based on primary production, which depends on a stable, benign climate for its prosperity. The costs of extreme weather events such as floods and droughts are already high, and are expected to get worse under a changing climate.
We are also distant from markets and customers, including our tourism markets, so there is a perception that the carbon footprint of our goods and services is high.
A number of sector-specific initiatives and policies are underway to reduce New Zealand’s greenhouse gas emissions. In addition, an economy-wide Emissions Trading Scheme has been announced to put a value on emissions from 2008. Both economy-wide action and sector-specific initiatives will be needed if we are to achieve significant reductions in emissions and accelerate the development of more low carbon technologies and practices.
Local action on climate change
Communities for Climate Protection – New Zealand
Communities for Climate Protection – New Zealand (CCP-NZ) is a voluntary programme which helps local government reduce greenhouse gas emissions from council operations and within their wider communities. CCP-NZ provides a framework in which actions can be taken to reduce greenhouse gas emissions through energy conservation, renewable energy, waste reduction, sustainable transport, improved urban design, and emission-reduction technologies.
Adapting 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 flooding substantially damaged stormwater infrastructure, roading, and private property.
While average rainfall in the Bay of Plenty is expected to decrease with climate change, extreme rainfall events and flooding 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 and upgraded stormwater infrastructure. The Council has also incorporated increased high intensity rainfall into its planning blueprint 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.
Protection of the ozone layer
Over the past 30 years, ozone levels over Antarctica have dropped by almost 60 per cent during the spring of each year and a ‘hole’ in ozone concentrations is clearly visible in satellite observations. This hole does not extend over New Zealand. In fact, New Zealand experiences its highest ozone levels in October, at the same time that the ozone hole occurs over Antarctica.
Nonetheless, summertime ozone levels over New Zealand continue to be strongly influenced by Antarctic ozone depletion. When New Zealand experiences a combination of lower ozone with high sun and few clouds, skin-damaging ultraviolet (UV) levels can be extreme.
Atmospheric ozone levels over New Zealand have varied considerably over time, as shown in Figure 3.3. Levels have stabilised in the last decade, reversing decreases in the 1980s and 1990s. Accordingly, monitored summertime UV levels in New Zealand have decreased in recent years. Also, atmospheric ozone levels over Antarctica are no longer reducing at the rate they were during the 1980s and 1990s.
(1) Five-year averages have been plotted to give an indication of trend in ozone concentration.
(2) DU = Dobson units.
Source: National Institute of Water and Atmospheric Research.
This graph displays ozone concentration measurements over New Zealand from 1970 until 2006. Concentrations from 1970 until the early 1980s were high typically in excess of 314 DU. Since the early 1980’s concentrations have been less than 314 DU. Lower levels (<300 DU)are particularly apparent in 1997, 1999, 2000 and 2006.
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 hold halon consumption at 1986 levels from 1992.
The provisions of the protocol have since been tightened through a series of amendments – CFCs and halons 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.
New Zealand is not a producer of ozone-depleting chemicals and it has regulated their import. Domestic controls reduce New Zealand’s reliance on ozone-depleting substances by progressively restricting the volumes imported. Since 2000, over 30,000 tonnes of halons have been collected for safe destruction.
New Zealand is the world’s 11th largest user of methyl bromide, an ozone-depleting substance that is used for maintaining biosecurity at New Zealand’s borders. The importation of methyl bromide for uses other than quarantine and pre-shipment treatments is now prohibited.
© Ministry for the Environment