Introduction to Climate Change

What is climate change? 

Greenhouse gases (including carbon dioxide and methane) trap heat in the earth’s atmosphere. Without them, too much heat would escape and earth’s surface would freeze. However, increasing the concentration of greenhouse gases in the atmosphere causes earth’s surface to heat more and the climate to change. 4864

The Intergovernmental Panel on Climate Change (IPCC) was set up in 1988 and is the international body for assessing the science related to climate change. 4865 The following are key facts from the Intergovernmental Panel on Climate Change’s Fifth Report (2014): 4866

  • Anthropogenic greenhouse gas emissions have increased since the pre-industrial era due to population growth and economic growth;
  • Atmospheric concentrations of carbon dioxide, methane and nitrous oxide are now higher than the last 800,000 years (they have increased from a preindustrial level of about 275 ppm of carbon dioxide to about 400 ppm of carbon dioxide);
  • Global land and ocean surface temperature rose 0.85°C between 1880 and 2012;
  • Global mean sea level rose by 0.19m between 1901 and 2010;
  • Continued emission of greenhouse gases will cause further warming and changes in the climate system with increasing impacts for people and ecosystems; and 
  • Limiting climate change will require substantial and sustained reductions in greenhouse gas emissions which, together with adaptation, can limit climate change risks. 

Climate change and New Zealand  

In 2017, the Ministry for the Environment published the report Our Atmosphere and Climate as part of their Environmental Reporting Series. The report emphasized that human-induced climate change is the most dominant issue for atmosphere and climate. 

The following key facts are drawn from the report: 4926

  • 24% rise in New Zealand's gross greenhouse gas emissions since 1990. While agriculture makes up nearly half of New Zealand's emissions, road transport has one of the largest increases in emissions, with a 78% increase since 1990;
  • 2016 was New Zealand's hottest year on record. New Zealand has experienced a 1C increase in temperature since 1990;
  • An average of 27 summer days with extreme UV intensity in 2016;
  • 169,000 hectares of deforested land since 2000. In 2015 New Zealand's native and exotic forests removed 67% of our carbon dioxide emissions. If deforestation continues to outpace the area of new forest planted, it will reduce the amount of carbon dioxide absorbed from the atmosphere by our forests;
  • Since 1977, 25% of glacier ice has been lost;
  • Since 1916, there has been 14-22cm sea-level rise at four main ports; and 
  • In the last 19 years, the pH of New Zealand's ocean has decreased by 0.03. This small decrease in pH amounts to a substantial increase in acidity which has numerous effects on living organisms. For example it makes it hard for shellfish to form shells and harms plankton which are two vital components of a healthy food chain. 

How will climate change affect New Zealand? 

Based on the latest scientific knowledge of climate change, over the next 50 years we are likely to experience higher temperatures, rising sea levels, more frequent extreme weather events and a change in rainfall patterns. 

These issues and their impacts are summarised in the table below. 



Higher temperatures

  • There is likely to be an increase in demand for air-conditioning systems and therefore electricity in summer.

  • People are likely to enjoy the benefits of warmer winters with fewer frosts, but hotter summers will bring increased risks of heat stress and subtropical diseases.

  • There may be a reduction in demand for winter heating meaning lower costs and reduced stress on those who cannot afford electricity. 


  • More frequent intense winter rainfalls are expected to increase the likelihood of rivers flooding and flash flooding when urban drainage systems become overwhelmed.

Water resources

  • Water demand will be heightened during hot, dry summers.

  • Longer summers with higher temperatures and lower rainfall will reduce soil moisture and groundwater supplies.

  • Drought intensity will likely increase over time. Drier conditions in some areas are likely to be coupled with more frequent droughts.

  • River flows are likely to be lower in summer and higher in winter.

  • Lower river flows in summer will raise water temperatures and aggravate water quality problems (eg, through increased algae growth).

Sea-level rise
  • Rising sea levels will increase the risk of erosion, inundation and saltwater intrusion, increasing the need for coastal protection.


  • Higher levels of human mortality related to summer heat are expected.

    Higher winter temperatures may lead to a reduction in winter related human mortality and illnesses such as colds and flu.


  • Warmer temperatures will alter habitats that are critical to some species, increasing the risk of localised extinction.

  • Warmer temperatures will favour conditions for many exotic species as well as the spread of disease and pests, affecting both fauna and flora.

  • Increased summer drought will put stress onto dry lowland forests.

  • Earlier springs and longer frost-free seasons could affect the timing of bird egg-laying and the emergence, first flowering and health of leafing or flowering plants.

Built environment

  • Increased temperatures may reduce comfort of occupants in domestic, commercial and public buildings and could lead to disruptions to business.


  • Hotter summers may damage elements of transport infrastructure causing buckled railway lines and damaged roads, with associated disruption and repair costs.
  • Agricultural productivity is expected to increase in some areas but there are risks of drought and spreading of pests and diseases.
  • There are likely to be costs associated with changing land-use activities to suit a new climate.

Business and Finance

  • Households may find it more difficult to access adequate insurance cover in the face of increased flood risk.

  • Fruit and vegetable growers may find it more expensive to insure against weather related damage (eg, from hail).

  • The risk management of potential climate change impacts may provide significant opportunities for businesses.

Impacts of climate change (Source: Ministry for the Environment, 2017)





Last updated at 9:05AM on April 9, 2018