Study shows recent sea levels rose at double the previously reported

A recent study has shown that sea levels have risen at double the reported rate over the past few decades. Through analysis of this historical data, the study has validated models predicting future sea-level rise.

The study was conducted by global professional services company GHD alongside Netherlands-based flood risk experts HKV, on behalf of Christchurch City Council. It is the first publication in New Zealand to find a material acceleration in sea level rise based on real-life data.

This is higher than previously recognised - the Ministry for the Environment had reported the average rate of sea level rise to be 2.7mm/year based on data collected over a 57-year period from 1961 to 2018.

By analysing data collected from between 2005 and 2020, this study has shown that sea-level rise in Lyttelton, Christchurch has averaged 7mm/year. The study also carried out a similar process over a longer period, from 1990 to 2020, which indicated an average rate of sea level rise to be 4mm/year.

These new findings are more consistent with climate change science and future predictions prepared by computer modelling (5-7 mm/year of sea level rise during the next decade “MfE 2017 Guide, Table 10, 2020-2030, RCP 2.6M and RCP 8.5H+”). Until now, this prediction had relied heavily on confidence in computer modelling and there had been a significant difference to reported sea level trends in New Zealand.

Tim Preston, Lead Water Engineer, led this project on behalf of GHD. He said “this result, while only at a single location, now shows alignment between actual historical data and computer modelled predictions of the future. This is measured evidence that accelerating sea-level rise is a reality now, and not just a hypothetical future problem. This data will improve confidence across the infrastructure industry in following the Ministry for the Environment issued guidance on future sea level changes. We hope this will increase attention to recent trends and prompt similar assessments at other NZ sea level monitoring sites”.

Christchurch City Council have published the report on their website at https://www.ccc.govt.nz/environment/coast/tidal-data/

For further information contact:

Jo Wyld
Communication Advisor
Jo.Wyld@ghd.com

About GHD:

GHD is a leading professional services company operating in the global markets of water, energy and resources, environment, property and buildings, and transportation. Committed to a vision to make water, energy and urbanisation sustainable for generations to come, GHD delivers engineering, architecture, environmental and construction solutions to public and private sector clients. Established in 1928 and privately owned by its people, GHD’s network of 10,000+ specialists are connected across 200 offices located in five continents and the Pacific region. www.ghd.com