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Sea-level rise around New Zealand over the next 90 years may not be as dramatic as some predict, former University of Otago school of surveying dean Prof John Hannah says. The data did not show any recent acceleration in sea-level rise, he said.

His research, carried out in conjunction with two others, indicates sea levels could rise by 0.5m to 0.8m by 2100, with the rise fairly consistent around the country.

While that matches predictions made by the Intergovernmental Panel on Climate Change, it is a more conservative estimate than what some have predicted.

In a report commissioned by the Dunedin City Council last year, University of Otago Emeritus Prof of geography Blair Fitzharris predicted an upper sea level rise limit of 1.6m for Dunedin by 2090 – enough to inundate South Dunedin, St Kilda and St Clair and affect the harbourside area, the lower Taieri Plain, Dunedin International Airport and settlements along the coast north of Dunedin.

United States physicist Dr James Hansen, dubbed “the grandfather of climate change”, who spoke to an audience of 1000 in Dunedin in May, predicts sea-level rises of 5m globally by 2100, with 4m of that rise occurring between 2080 and 2100.

Prof Hannah and his research partners, Niwa principal coastal scientist Dr Rob Bell and Ryan Paulick from the former Auckland Regional Council, analysed data from numerous tidal gauges around the country and information from other sources to reach their conclusions.

Prof Hannah said this week the tidal gauge data, which stretched back 100 years for Auckland, Wellington, Christchurch and Dunedin, was “very robust” and enabled them to say New Zealand could reasonably expect sea-level rises of between 0.5m and 0.8m by 2100.

Also, the data did not show any recent acceleration in sea-level rise, he said.

“Temperatures will rise and sea levels will rise, we know that. It looks like New Zealand temperatures will revert back to where they were 3000-4000 years ago during the mid-Holocene period.” The evidence was that sea levels at that time were about 0.5m-0.8m higher than they were now, he said.

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