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. 

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

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