How climate change will affect Christchurch

Our average temperature will rise from 0.5°C to 1.5°C by 2040, and 3.0°C by 2090.

Our average maximum temperature will rise by 3 to 4⁰C by 2090.

Our average minimum temperature will rise by 1 to 2⁰C by 2090.

Our number of days over 25°C will increase:

• 10+ more days over 25°C per year by 2040.
• 20+ more days over 25°C per year by 2090 for Christchurch.
• Up to 40 more days over 25°C per year in parts of Banks Peninsula.

Our number of frosts will decrease:

• 10 fewer frosts per year by 2040.
• 20 fewer frosts per year by 2090, and significantly fewer than this for inland areas.

Our seasonal temperature will change – particularly in autumn when summer will extend.

What this will mean

• Heat stress will affect the health of people, animals and plants.
• Heating costs will decrease in winter, cooling costs will increase in summer.
• Demand for drinking water will increase when water is likely to be scarcer.
• Risk of wildfire will increase, especially in high winds and drought,  when water is scarce for firefighting.
• Water quality will deteriorate, made worse by increased water use for human activity.
• Ecosystems will be under threat. Some species will become extinct.
• Loss of biodiversity will impact mahinga kai and customary practices.
• Current agriculture and horticulture will be at risk of new pests and diseases. Higher temperatures may allow different crops to be grown.
• Summer leisure and tourism season will be extended, but the ski season will be shorter and glaciers will be disappearing.

Average rainfall will not change much, but summer and autumn will be drier with 5 to 15 per cent less summer rainfall for Banks Peninsula.

Winters will be wetter - up to 10 per cent more rainfall.

There will be long dry periods with more intense, more frequent drought and more frequent and more extreme rainfall events.

What this will mean

• Less water available for drinking, irrigation, and agriculture during drought, especially on Banks Peninsula. Average river flows may be 20 per cent less by 2090.
• Rivers will flood more often . More flash flooding of communities and businesses will affect people, the economy, and Ngāi Tahu cultural values and mahinga kai.
• More frequent surface flooding. Flood water will damage bridges, roads and other infrastructure.
• Insurance costs for homes and businesses may increase or become unavailable in areas most at risk. 
• Parks and sports grounds will be affected by both drought and flooding.
• Drought and fires will reduce vegetation on hills, increasing landslides and erosion during intense rainfall and strong winds. There could be permanent loss of soils in Banks Peninsula, preventing revegetation.
• Increased erosion will lead to more sediment in waterways, reducing water quality and stream capacity. 
• Indigenous ecosystems, plants and animals, will be under threat,  especially during drought.

Sea levels:

Levels are projected to rise over time: 

• 0.3m by 2050
• 0.5m by 2075
• 1.0m by 2115

Groundwater will be closer to the surface (more shallow).

More frequent and intense flooding and erosion from storm surges.

Groundwater will become salty. Saltwater will move further upstream in rivers.

What this will mean

• More frequent, more severe coastal flooding will affect people’s  health, wellbeing and the economy
• Saltwater getting into freshwater systems will reduce habitats
• Taonga species and mahinga kai will be lost
• Salty groundwater close to the surface will damage buried pipes and foundations of roads and buildings. It can result in cold, damp homes.
• There could be long-term standing surface water, which may attract insects and exacerbate flooding issues.
• Coastal erosion may lead to loss of road access to communities in Banks Peninsula
• Coastal and low-lying communities will need to adapt to sea level rise, or relocate.
• Our population may grow due to climate refugees from other countries.
• Wāhi tapu, wāhi taonga and cultural landscapes may be adversely affected, or lost.

The ocean and sea:

The ocean will become more acidic

Seawater will be warmer

There will be marine heatwaves

What this will mean

• Marine ecosystems will be altered, particularly affecting hard-shelled species
• Some species will become extinct
• Changes to the range of species, location and abundance of fish and sea birds around New Zealand will impact the food chain
• Aquaculture and fishing industries will be impacted
• Taonga species and mahinga kai will be lost
• Recreational benefits will be reduced.

Wind speeds may increase up to 5% by 2100.

What this will mean

• Trees, buildings and power lines will be damaged more frequently
• Fire risk will increase during hot, dry period and soil will dry quicker, increasing demand on water supply
• Wind powered electricity generation will be more viable.