Climate change projections for the Nelson-Tasman region

Map of Nelson-Tasman region. This page provides an overview of how the climate in the Nelson-Tasman 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 0.6˚C to 3.0˚C warmer by 2090.

By 2090, some parts of Nelson-Tasman are projected to have from 5 to 43 extra days per year where maximum temperatures exceed 25˚C, with around 9 to 28 fewer frosts per year.

Rainfall

Rainfall will vary locally within the region. The largest changes will be for particular seasons rather than annually.

Seasonal projections show summer, autumn and winter rainfall increasing by up to 10, 7 and 11 per cent respectively in Nelson by 2090, with little change in spring rainfall.

Extreme rainy days are likely to become more frequent throughout the Nelson-Tasman region by 2090 under the highest emissions scenario.

Snowfall

A reduction in the number of snow days experienced annually is projected throughout New Zealand, including the Nelson-Tasman region. The duration of snow cover is also likely to decrease, particularly at lower elevations. Places that currently receive snow are likely to see a shift towards increasing rainfall instead of snowfall as snowlines rise to higher elevations due to rising temperatures.

Wind

The frequency of extremely windy days in the Nelson-Tasman region by 2090 is not likely to change significantly. There may be an increase in westerly wind flow during winter, and north-easterly wind flow during summer.

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 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
  • 1 per cent less to 1 per cent more rainfall in Nelson

Summer

  • 0.6°C to 3.2°C temperature rise
  • No change to 10 per cent more rainfall in Nelson

Autumn

  • 0.7°C to 3.2°C temperature rise
  • 3 to 7 per cent more rainfall in Nelson

Winter

  • 0.7°C to 3.1°C temperature rise
  • 4 to 11 per cent more rainfall in Nelson

*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 Nelson-Tasman?

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

Heavy rain – The capacity of stormwater systems may be exceeded more frequently due to heavy rainfall events which could lead to surface flooding. River flooding and hill country erosion events may also become more frequent.

Drought – By 2090, the time spent in drought ranges from minimal change through to more than double. More frequent droughts are likely to lead to water shortages, increased demand for irrigation and increased risk of wild fires.

Disease - There may be an increase in the occurrence of summer water-borne and food-borne diseases such as Salmonella. There may also be an increase in tropical diseases.

Biosecurity – Climate change could increase the spread of pests and weeds. Warmer temperatures will make pests such as mosquitoes, blowflies, ants, wasps and jellyfish more prevalent in the region. Similarly, crop diseases such as fungi and viruses may penetrate into the region where currently they are excluded by lower temperatures. There may also be a loss of habitat for native species.

Agriculture – Warmer temperatures, a longer growing season and fewer frosts could provide opportunities to grow new crops. Farmers might benefit from faster growth of pasture and better crop growing conditions. Horticultural crops, such as kiwifruit and wine grapes, are likely to show the greatest gains from higher average temperatures. However, these benefits may be limited by negative effects of climate change such as prolonged drought 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.

Find out more

Nelson City Council’s climate change information [Nelson City Council website]

Tasman District Council’s climate change information [Tasman District Council website]

Reviewed:
30/06/16