Climate change projections for the Canterbury region

Map of Canterbury region.

This page provides an overview of how the climate in the Canterbury region is likely to change into the future and what implications this has for the region.

Projections of climate change depend on future greenhouse gas emissions, which are uncertain. There are four main global emissions scenarios ranging from low to high greenhouse gas concentrations. This page presents regional projections as a range of values from a low emissions to a high emissions future.

The projected changes are calculated for 2031–2050 (referred to as 2040) and 2081–2100 (2090) compared to the climate of 1986–2005 (1995).

Temperature

Compared to 1995, temperatures are likely to be 0.7˚C to 1.0˚C warmer by 2040 and 0.7˚C to 3.0˚C warmer by 2090.

By 2090, Canterbury is projected to have from 6 to 35 extra days per year where maximum temperatures exceed 25˚C and the number of frosts could decrease by around 13 to 38 per year.

Rainfall

Rainfall will vary locally within the region. The largest changes in rainfall are likely to be for particular seasons rather than annually.

By 2090, winter rainfall is projected to decrease by up to 12 per cent in Christchurch and up to 10 per cent in Hanmer, but increase by 6 to 28 per cent in Tekapo.

According to these latest projections, the frequency of extreme rainy days in the Canterbury region is not projected to significantly change as a result of climate change. Under the highest emissions scenario, there is likely to be a small increase in frequency by 2090.

Snowfall

The Canterbury region will likely experience significant decreases in seasonal snow. By 2090 the number of snow days is projected to decrease by up to 30 days per year. The duration of snow cover is also likely to decrease, particularly at lower elevations.

Less winter snowfall and an earlier spring melt may cause marked changes in the annual cycle of river flow in the regions. Places that currently receive snow are likely to see increasing rainfall as snowlines rise to higher elevations due to rising temperatures. So for rivers where the winter precipitation currently falls mainly as snow and is stored until the snowmelt season, there is the possibility of larger winter floods.

Wind

The frequency of extremely windy days in Canterbury by 2090 is likely to increase by between 2 and 10 per cent. Changes in wind direction may lead to an increase in the frequency of westerly winds over the South Island, particularly in winter and spring.

Sea-level rise

New Zealand tide records show an average rise in relative mean sea level of 1.7 mm per year over the 20th century. Globally, the rate of rise has increased and further rise is expected in the future.

The Ministry for the Environment provides guidance on coastal hazards and climate change, including recommendations for sea level rise, see Preparing for coastal change: A guide for local government in New Zealand.  An updated edition will be published in late 2016.

Impacts by season

By 2090, the region could expect*:

Spring

  • 0.6°C to 2.6°C temperature rise
  • No change to 2 per cent more rainfall in Christchurch
  • 1 to 2 per cent more rainfall in Hanmer
  • 6 to 13 per cent more rainfall in Tekapo

Summer

  • 0.6°C to 3.0°C temperature rise
  • 1 to 8 per cent more rainfall in Christchurch
  • No change to 9 per cent more rainfall in Hanmer
  • 2 to 5 per cent more rainfall in Tekapo

Autumn

  • 0.7°C to 3.0°C temperature rise
  • No change to 8 per cent more rainfall in Christchurch
  • No change to 2 per cent more rainfall in Hanmer
  • 2 per cent less to 3 per cent more rainfall in Tekapo

Winter

  • 0.7°C to 3.3°C temperature rise
  • 12 per cent less to 1 per cent more rainfall in Christchurch
  • 10 per cent less to 1 per cent more rainfall in Hanmer
  • 6 to 28 per cent more rainfall in Tekapo

*Projected changes are relative to 1995 levels. The values provided capture the range across all scenarios. They are based on scenario estimates and should not be taken as definitive. For more information, see the full report on climate projections.

What could this mean for Canterbury?

Water shortages – Higher temperatures, less rainfall and greater evapotranspiration are likely to cause increasing pressure on water resources, particularly in North Canterbury.  Droughts are likely to become more frequent and more extreme.

Fire risk – Strong winds, combined with high temperatures, low humidity and seasonal drought may result in an increased fire risk in some areas (such as Christchurch, Kaikoura, and Darfield). The length of the fire season is expected to increase.

Sea level rise – As the climate changes and the sea level rises, it is likely that Christchurch will face increased flooding in some areas, particularly around the lower Avon River . Coastal erosion is likely to increase.

Biosecurity – Climate change could increase the spread of pests and weeds. Banana passionfruit, a frost-tender plant, appears to be spreading, and argentine ants have survived through two winters, which was previously not thought possible. There may also be an increased threat to native species from changed distribution of disease vectors.

Agriculture – Warmer temperatures, a longer growing season and fewer frosts could provide opportunities to grow new crops. Farmers might also benefit from faster growth of pasture and better crop growing conditions. However, these benefits may be limited by negative effects of climate change such as prolonged drought, increased flood risk, and greater frequency and intensity of storms. There is also likely to be increasing pressure on water resources.

The Ministry for Primary Industries website and associated website Climate Cloud have more information on the regional impacts of climate change on agriculture.

Find out more

Environment Canterbury's climate change information [Environment Canterbury website]

Reviewed:
30/06/16