What is climate change?
Climate change describes how the average weather patterns over New Zealand, and their extremes, will change from their current state. This change is being predicted as a result of the "global warming" of the Earth, caused by the emission of greenhouse gases.
Why does climate change matter?
Some of the key impacts of climate change for New Zealand are:
- Sea level rise: sea levels around New Zealand are expected to rise due to the ocean expanding as it warms, as well as the melting of glaciers. Sea level rise around New Zealand is likely to be similar to global projections. This rise depends on the amount of warming, and critically on the response of glaciers in Greenland and Antarctica.
- Heavy rainfall and flooding: a warmer atmosphere can hold more moisture (about 7% more for every 1°C increase in temperature). Modelling work suggests that for New Zealand all rainfall extremes can be expected to increase by about this amount. On top of this, local atmospheric circulation changes can further increase or decrease rainfall extremes.
- Drought: droughts are projected to become more frequent and more intense under climate change. Droughts represent a significant cost to the agricultural sector of the New Zealand economy.
- Strong winds: climate models suggest that the frequency of extreme winds over New Zealand is likely to increase in almost all areas in winter, and decrease in summer. Increases in strong winds may mean that coastal regions exposed to the prevailing winds may be subject to an increase in the frequency of heavy swells, which would add to the effects of higher sea levels
- Daily temperature extremes and frosts: in addition to changes in mean temperature, daily temperature extremes will also vary with regional warming. A large decrease in the number of frost days is projected for the central North Island and in the South Island as the 21st century progresses. An increase in the number of days above 25°C is also expected, particularly at already warm northern locations. High temperature extremes are known to have impacts on human health as well as economic costs.
- Biological systems: higher temperatures could favour conditions for the increased spread of exotic diseases and pests, affecting both fauna and flora.
For the Waikato, the likely impacts include:
- 0.7 to 1.1°C warmer by 2040 and 0.7 to 3.1 °C warmer by 2090.
- The time spent in drought is likely to increase. More frequent droughts are likely to lead to water shortages, increased demand for irrigation and increased risk of wild fires.
- Spring rainfall is likely to increase by 5% by 2090. Annual rainfall is likely to increase by 2% by 2090.
Source: Ministry for the Environment
What has caused climate change?
Since the industrial revolution, there has been a marked and growing increase in greenhouse gas producing activities such as industry, agriculture and transportation. These activities are increasing the level of greenhouse gases in the atmosphere. They are causing the Earth to heat up at a rate unprecedented in recent history. This recent warming can only be explained by the influence of humans.
Source: Ministry for the Environment
What are carbon emissions?
Carbon emissions, also known as greenhouse gas emissions, are gases that are added to the atmosphere through human activities. This does not include natural sources such as biological processes or volcanic emissions. We report greenhouse gas (GHG) emissions in carbon dioxide equivalent (CO2e) units, which is a measure for how much global warming a given type and amount of greenhouse gas causes, using the equivalent amount of carbon dioxide as the reference. CO2e is used for describing different greenhouse gases in a common unit, which allows them to be reported consistently.
Source: Statistics New Zealand
What are biogenic emissions arising from wastewater treatment?
Biogenic methane (CH4), which has 25 times the global warming potential (GWP) of CO2 over a 100-year time period, is produced by methanogenic bacteria in the sewer network during breakdown of the fats, proteins and carbohydrates that constitute the bulk of the organic matter in the wastewater.
The production of biogenic nitrous oxide (N2O), which has 298 times the GWP of CO2 may also occur in the wastewater treatment process.
What is the difference between renewable and non-renewable energy?
Non-renewable energy resources cannot be replaced. Once they are used up, they will not be restored (or not for millions of years). Non-renewable energy resources include fossil fuels such as coal, oil, natural gas and nuclear power.
Renewable energy comes from sources that can be replaced. Examples include energy from the sun (solar), wind, moving water (hydro) and plants such as pine forests, which supply firewood. This energy is harnessed to drive generators that produce electric power.