Archived publication
This publication is no longer current or has been superseded.
Background
Greenhouse gases in the Earth’s atmosphere trap warmth from the sun and make life possible. However, over the past 50 to 100 years, the concentration of greenhouse gases such as carbon dioxide, methane and nitrous oxide has been increasing. This increased concentration produces an ‘enhanced greenhouse effect’ where more of the sun’s warmth is trapped by the atmosphere. The majority of experts agree that the enhanced greenhouse effect is causing global warming. Predicted changes in the climate are expected to be much greater and happen more quickly than any recent natural changes.
This document presents a summary of the latest information on New Zealand’s greenhouse gas emissions and removals. The information is taken from the most recent national inventory report under the United Nations Framework Convention on Climate Change (New Zealand’s Greenhouse Gas Inventory 1990–2005). The inventory reports only human-induced emissions and removals of greenhouse gases. Each inventory report is 15 months in arrears allowing time for data to be collected and analysed.
There is statistical uncertainty around the values reported in national inventories. For New Zealand, the uncertainty in any one year is approximately ± 20 per cent, dominated by uncertainty in emissions from farming and forestry. Uncertainty in the trend since 1990 is only ± 5 per cent, because the uncertainty in emissions factors in any one year cancels out over time.
Greenhouse gas estimates are based on international guidance established by the Intergovernmental Panel on Climate Change (IPCC) and follow an internationally agreed reporting format that groups emissions and removals into six sectors:
-
Agriculture
-
Energy (including transport)
-
Industrial Processes
-
Solvent and Other Product Use
-
Waste
-
Land Use, Land-Use Change and Forestry.
The greenhouse gases estimated in the national inventory include carbon dioxide (CO2), methane (CH4), nitrous oxide (N2O), sulphur hexafluoride (SF6), perfluorocarbons (PFCs) and hydrofluorocarbons (HFCs). To compare the warming effect of different gases, all emissions are converted to carbon dioxide equivalents (CO2-e). This is achieved by multiplying emissions by the appropriate global warming potential. The global warming potential is the relative warming effect of a gas when compared with the same mass of carbon dioxide.
Table 1: Units and common global warming potentials
Units
Standard metric prefixes used in this report are:
kilo (k) = 103 (one thousand)
mega (M) = 106 (one million)
giga (G )= 109 (one thousand million)
Emissions are generally expressed in megatonnes (Mt) in this report. Numbers are rounded to one decimal place (this can lead to rounding errors in some figures)
1 megatonne (Mt) = 1,000,000 tonnes = 1,000 Gg
Common Global Warming Potentials
CO2 = 1
CH4 = 21
N2O = 310
SF6 = 23,900
The United Nations Framework Convention on Climate Change
The United Nations Framework Convention on Climate Change (UNFCCC) is an international agreement which addresses climate change. All countries that ratify the UNFCCC are required to tackle climate change through national or regional programmes. This includes preparing for the impacts of climate change and monitoring emission trends. Developed countries agreed to non-binding targets to reduce greenhouse gas emissions to 1990 levels by the year 2000.
Developed countries that are signatories to the UNFCCC – including New Zealand – are required to submit an annual greenhouse gas inventory. Inventory reporting covers all human-induced emissions and removals. In New Zealand, this reporting is undertaken by the Ministry for the Environment, with information collected across a number of government agencies. The inventory forms part of the nation’s wider ‘state of the environment’ reporting.
The Kyoto Protocol
The international community recognised that the provisions of the UNFCCC alone were not enough to ensure greenhouse gases would be reduced to safe levels and that more urgent action was required. In 1997, the Kyoto Protocol was adopted, committing Annex I Parties (developed countries) that have ratified it to a legally-binding target to reduce their greenhouse gas emissions or to take responsibility for excess emissions.
New Zealand ratified the Kyoto Protocol in December 2002, with a target of 100 per cent of 1990 emissions. This means that New Zealand is liable for any emissions – above 1990 levels – for the period 2008 to 2012. The Kyoto Protocol came into force on 16 February 2005.
The national inventory report is the basis of all accounting under the Kyoto Protocol.
