Climate change projections for the Southland region

Map of Southland region. This page provides an overview of how the climate in the Southland 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 0.6˚C to 0.9˚C warmer by 2040 and 0.6˚C to 2.8˚C warmer by 2090.

By 2090, Southland is projected to have up to 16 extra days per year where maximum temperatures exceed 25˚C, with around 10 to 30 fewer frosts per year.

Rainfall

Southland is expected to become wetter, particularly in winter and spring. Seasonal projections show winter rainfall increasing by 7 to 22 per cent in Invercargill by 2090.

According to the most recent projections, extreme rainy days are likely to become more frequent in Southland by 2090 under the highest emissions scenario.

Snowfall

The Southland region is likely to experience significant decreases in seasonal snow. By the end of the century, the number of snow days experienced annually could decrease by up to 30 days in some parts of the region. 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 region. 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 for larger winter floods.

Wind

The frequency of extremely windy days in Southland by 2090 is likely to increase by between 2 and 7 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.

Storms

Future changes in the frequency of storms are likely to be small compared to natural inter-annual variability. Some increase in storm intensity, local wind extremes and thunderstorms is likely to occur.

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 is due for release in 2017.

Impacts by season

By 2090, the region could expect*:

Spring
  • 0.5°C to 2.4°C temperature rise
  • 6 to 15 per cent more rainfall in Invercargill

Summer

  • 0.5°C to 2.8°C temperature rise
  • 1 to 6 per cent more rainfall in Invercargill

Autumn

  • 0.7°C to 2.8°C temperature rise
  • No change to 4 per cent more rainfall in Invercargill

Winter

  • 0.7°C to 3.0°C temperature rise
  • 7 to 22 per cent more rainfall in Invercargill

*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 Southland?

Flooding – Climate change is expected to increase the risk of flooding, landslides and erosion in Southland. The capacity of stormwater systems may be exceeded more frequently due to heavy rainfall events which could lead to surface flooding, damage to infrastructure and road closures.

Water availability – Water security is most likely to be an issue in parts of Southland where drought is already a major constraint. Droughts are likely to increase in both intensity and duration over time. In other areas, such as around Invercargill, drought severity and irrigation demand may decrease slightly as average annual rainfall increases.

Coastal hazards – There is likely to be increased risk to coastal roads and infrastructure from coastal erosion and inundation, increased storminess and sea-level rise.

Biosecurity – Warmer temperatures, particularly with milder winters, could increase the spread of pests and weeds.

Agriculture – Warmer temperatures, a longer growing season and significantly fewer frosts could provide opportunities to grow new crops. Farmers might benefit from faster growth of pasture and better growing conditions. However, these benefits may be limited by negative effects of climate change such as increased flood risk or greater frequency and intensity of storms.

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

Reviewed:
30/06/16