How is climate change affecting Tasman District?

The sea level is rising around the District and will have some impact on the present coastline and coastal communities.

As water warms it expands. Even if the glaciers and icesheets stay stable there will still be a certain amount of sea level rise. However we are expecting that with increasing global temperatures there will be further glacial and icesheet retreat in the future. For those glaciers and icesheets on land, the melt will lead to a sea level change.

Historic sea level rise in New Zealand has averaged 1.78mm per year, with the Port Nelson tide gauge recording a slightly lower rate than the national relative average of 1.57mm per year (MfE, 2017). Measured sea levels at Port Nelson have risen approximately 150mm since the early 1940s.

The rate and magnitude of future sea level rise is uncertain, especially later this century and beyond. Scientists advise that sea levels will continue to rise and that levels are likely to rise at an accelerated rate over time as the earth’s temperature rises, meaning changes could happen sooner than predicted – or there may be changes to emission rates that reduce the rate of warming.

Uncertainty is a key message. What we do know is that rising sea levels will have increasing implications for development and infrastructure in coastal areas along with environmental, cultural and societal effects.

Ex-tropical cyclone Fehi was a significant coastal storm inundation event that effected our district on 1 February 2018. The large storm surge which coincided with a high spring tide and large waves damaged the coastline and flooded roads, reserves and nearby properties and houses. Sea level rise will increase the exposure of our coastal land to these type of events, creating new hazards in areas that have not previously been exposed.

We're starting a community discussion around climate change and sea level rise. We need everyone to join in.

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This report expands on the 2015 NIWA climate change report for Tasman District by introducing six additional climate change variables. These variables have been found to give the most accurate results when compared to historical climate and circulation patterns in the New Zealand and southwest Pacific region. The report describes changes that may occur to Tasman’s climate over the next 80 years, and describes the impacts of these changes on agricultural systems.

Download a copy of the report. (pdf, 7.4 MB)

Key points are:

• The Tasman District will likely experience a warmer and wetter climate, with increased seasonal climate extremes.
• Drought intensity may increase in the summer and heavy rainfall may increase in the winter and spring.
• Ex-tropical cyclones will continue to affect the region from time to time, and the rainfall intensity from those systems may increase.
• Frost incidence is likely to fall, and the occurrence of high temperatures and heatwaves will increase.
• The highly flexible land classes in coastal lowland areas such as Waimea Plains, around Motueka and Takaka, and in valleys further inland, are already the warmest parts of the region and will become warmer in the future.
• For less flexible land (e.g. around Motupiko, Lake Rotoiti and Bainham), if these areas are limited by cold conditions rather than other factors such as soil type and topography, future warming presents an opportunity for these areas to become more flexible.
• Increasing drought intensity across the region, but particularly in central areas. In summer, pasture and crop growth may be impacted and consequently, increase the need for irrigation, as well as increasing fire risk in forested areas.
• Winter rainfall is projected to increase, and extreme rainfall events may increase in intensity, potentially causing more slips on hill country farmland and deforested areas.
• The Tasman District is projected to experience increased heatwave conditions compared to historic levels, but the southern part of the region is likely to be disproportionately affected. This brings a range of effects, from animal health (heat stress, milk production) to plant development (weed growth, increased or decreased productivity of crops, shifts to drought resistant crops).

In 2015, NIWA released a climate change and variability report for Tasman District Council. The report describes changes which may occur over the coming century in the climate of the Tasman region, and outlines some of the possible impacts of these changes.

Download a copy of the report:

• Climate Change and Variability - NIWA Report for Tasman District Council, August 2015 (pdf, 5.5 MB)

The key points from this report are:

• New Zealand has warmed by 0.9 +/-0.3 °C since 1909.
• There has been a rise in sea level of around 190 mm, or approximately 1.7 mm/yr since 1900. Globally, the rate of rise has increased and further rise is expected in the future.
• The ocean is becoming more acidic as it aborbs carbon dioxide.
• Compared to 1995, temperatures in Tasman District are likely to be 0.7°C to 1°C warmer by 2040 and 0.6°C to 3°C warmer by 2090.
• By 2090, some parts of the Nelson-Tasman region 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 will vary locally within the region. Seasonal projections show summer, autumn and winter rainfall increasing by up to 10, 7 and 11 % respectively by 2090, with little change in spring rainfall. Extreme rainy days are likely to become more frequent throughout the Nelson-Tasman region by 2090.
• An increase in drought frequency is projected for the plains adjacent to Tasman Bay of about 5% for 2030-2050 and 10% for 2070-2090, compared to 1980-1999 levels.
• A reduction in the number of snow days experienced annually is projected, along with a decrease in the duration of snow cover, particularly at lower elevations.
• 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.
• 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.

Impacts by season

By 2090, the Nelson-Tasman region could expect*:

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

On Wednesday 3 August 2011, Tasman District Council hosted two leading New Zealand specialists to explain the nature of climate change, its impacts in New Zealanders' health, properties, infrastructure, environment and rural industries.

Dr Jim Salinger, Auckland Climate Scientist, and Rod Oram, Business Journalist, spoke to a crowd of over 130 on "Maintaining farm productivity and profits in an uncertain climate".

Please follow these two links below to view the presentation:

• Climate Change Seminar presentation by Rod Oram and Dr Jim Salinger (pdf, 3.6 MB)
• View the Tasman Climate Change Seminar on YouTube