This page provides an overview of how the climate in the Otago 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).
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, Otago is projected to have from 4 to 25 extra days per year where maximum temperatures exceed 25˚C, with around 13 to 45 fewer frosts per year.
Rainfall will vary locally within the region. The largest changes will be for particular seasons rather than annually.
Otago is expected to become wetter, particularly in winter and spring. Seasonal projections show winter rainfall increasing by 4 to 10 per cent in Dunedin and 4 to 27 per cent in Queenstown by 2090.
According to the most recent projections, extreme rainy days are likely to become more frequent in Otago by 2090 under the highest emissions scenario.
The Otago 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 as much as 30-40 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.
The frequency of extremely windy days in Otago by 2090 is likely to increase by between 2 and 5 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.
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.
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, seasonally the region could expect*:
*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 Otago?
Flooding – More heavy rainfall will increase the risk of flooding and landslides, particularly in western Otago. Lakeside communities such as those around Lakes Wakatipu and Wanaka, as well as those further downstream alongside the Clutha River could face greater risk from floodwaters.
Drought – By 2090, the time spent in drought ranges from minimal change through to more than double depending on the climate model and emissions scenario considered. More frequent droughts are likely to lead to water shortages, increased demand for irrigation and increased risk of wild fires. Reduced snowfalls may affect water availability since snow acts as a storage mechanism until the water is required in summer.
Coastal hazards – There may be increased risks to coastal roads and infrastructure from coastal erosion and inundation, increased storminess and sea-level rise. Rising sea levels and storm surge will increase the risk of salt-water intrusion in low-lying coastal areas such as South Dunedin (much of which is at or below sea level). The Harbourside and South City area is the most at risk from both rising groundwater levels and direct inundation from the sea.
Lakes – Higher temperatures and changes in rainfall are likely to result in higher lake levels on average in western and central parts of Otago and lower levels in some eastern areas. Warmer water temperatures could lead to more algal blooms, a reduced range of trout species and the spread of pest species like carp.
Biosecurity – Warmer temperatures, particularly with milder winters, could increase the spread of pests and weeds.
Agriculture – Warmer temperatures, a longer growing season and fewer frosts could provide opportunities to grow new crops, but with reduced winter chilling some crops may not remain viable.
With frost reduction and temperature increase, climate change could benefit cherries and apricots both in yield and quality. Farmers might 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.
Find out more
Dunedin City Council’s climate change information [Dunedin City Council website]