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Projections: climate change and sea level rise

Climate change will have an effect on sea levels, weather patterns and rainfall intensity. These changes in turn will increase natural hazard risks such as flooding from extreme rainfall, inundation (flooding from the harbour/sea), erosion (coastal and inner harbour), tsunami and liquefaction.

Sea level rise is going to have an increasing influence on our community over the coming decades and beyond. While there are many uncertainties about climate change, sea level rise and when rising seas will affect the existing hazards risks in Tauranga, it is clear from New Zealand and international research that there have been increases in sea levels across the world since the mid-1800s, and that this will continue well into the future.

Sea level rise scenarios

In our research we take a range of future sea level rise scenarios into account. These scenarios are based on guidance from the New Zealand government on coastal hazards and climate change.

Guidance on Coastal Hazards and Climate Change - MFE

Researchers world-wide, including the Intergovernmental Panel on Climate Change (IPCC), base their projections for sea level rise on four scenarios called Representative Concentration Pathways (RCPs), based on different greenhouse gas emissions levels: RCP2.6, RCP4.5, RCP6.0 and RCP8.5. This reflects the range of possibilities of how the world is going to manage greenhouse gas emissions, and therefore how the sea may respond.

Global projections

Across all four scenarios, IPCC research provides near certainty that by 2050, the global sea level rise will sit between 0.15m and 0.3m. However, uncertainty increases significantly towards the end of the century and beyond, when potential future reductions in global emissions could start having an impact.

So we need to be mindful of the constantly changing research behind sea level rise projections, and continue to use the most up-to-date research and guidance available. 

Projections for New Zealand

The projections for sea level rise around New Zealand, based on the different scenarios, vary between 0.23m and 0.37m in 2050, and 0.46m and 1.05m by 2100 as outlined in the guidance from the Ministry for the Environment on coastal hazards and climate change.

The projections for NZ and Tauranga include a fifth scenario in addition to IPCC’s four: H+. The H+ scenario reflects the possibility of future surprises, where more rapid rates of sea level rise could occur early next century.

These projections are shown in the graph below:

Sea level rise projections NZ graph

Projections for Tauranga

We commissioned NIWA to develop sea level rise scenarios for Tauranga Harbour for the next 100 years, as well as assess prior storm events to better understand potential inundation in the future.

The projected sea level rise (NZVD 16) for Tauranga Harbour using four greenhouse gas concentration scenarios are below:

Year NZ RCP2.6 (Median) NZ RCP4.5 (Median) NZ RCP8.5 (Median) NZ H+
1986-2005 0.07m 0.07m 0.07m 0.07m
2070 0.19m 0.23m 0.33m 0.49m
2130 0.47m 0.61m 1.05m 1.39m

You can read the detail in NIWA’s full analysis below. Please note, sea level rise projections in this report are presented as measured from Moturiki Vertical Datum 1953.

NIWA – Tauranga Harbour Extreme Sea Level Analysis (2017) (3mb pdf)

Last Reviewed: 26/08/2020

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