Sea level rise is one of the largest climate change hazards facing New Zealand – but new research suggests that many Kiwis don't have an accurate picture of the risk.
A new study, just published in the scientific journal PLOS ONE, has indicated nearly one in five Kiwis may over-estimate the projected amount of sea level rise this century.
While the researchers said there were obvious dangers with a public that downplayed the risk, there were problems, too, with over-estimating it.
Focusing on extreme and often unsound projections could lead to public anxiety and feelings of helplessness, rather than motivating people to take action, said the study's leader, Associate Professor Rebecca Priestley of Te Herenga Waka-Victoria University.
The average global sea level has risen by more than 16cm since 1900, but many of the 1100 people surveyed for the study either underestimated (38.2 per cent) or overestimated (35 per cent) the amount.
Nearly one in five over-estimated global sea-level rise projections to 2100, while three quarters were in line with scientifically plausible projections, selecting "up to 40cm" (28.6 per cent), "up to 1m" (30.9 per cent) and "up to 2m" (14.9 per cent).
Respondents were asked the maximum amount of sea-level rise that could occur if all the glaciers and ice sheets and ice caps on Earth melted.
The largest group over-estimated (38.9 per cent), selecting "about 120m" (17 per cent), "about 240m" (10.9 per cent) and "more than 500m" (11 per cent).
The next largest group (38.8 per cent) under-estimated, selecting "about 30m", while 22.3 per cent selected "about 60m", a figure broadly in line with scientific estimates.
Respondents were asked the fastest period the above scenario could occur.
While scientists suggested it was under a sustained warming climate over thousands of years, only 11.6 per cent were in line with this.
Of the rest, 33.1 per cent selected "decades" and 39 per cent selected "centuries".
Asked to identify and rank the major causes of sea-level rise from a 10-item list, 28.7 per cent put melting sea ice, which does not directly contribute to sea-level rise, first.
"Some of the most extreme projections selected by our respondents go beyond the 5m of sea-level rise by 2100 that some media have reported," wrote Priestley and study co-authors Zoë Heine, of Victoria's Centre for Science in Society, and Associate Professor Taciano Milfont, of the University of Waikato.
"For example, 6.8 per cent of respondents who thought [under "a scientifically credible worst-case scenario"] sea-level rise could reach '15m or more' by 2100 and the 33.1 per cent who believed that all the planet's ice could melt over a period of 'decades' selected options that are unprecedented in the geological record and defy physical laws around how fast ice can melt, even under extreme temperature forcing."
Priestley, an award-winning science communicator, non-fiction author and interdisciplinary scholar, said New Zealand needed to be talking about sea level rise as a country, and at regional and community levels, with the support of good scientific information.
"We need to prepare for and adapt to the sea-level rise we know is inevitable and to act now to reduce our carbon emissions to stop even higher rises," she said.
"If we can meet our commitments under the Paris Agreement on climate change, we should be able to limit sea-level rise around our coast to an average of 20cm by 2050 and 50cm by 2100, although there will be significant local variation and even this amount of sea level rise will have a significant impact and require adaptations."
The study was hosted by the Te Herenga Waka-hosted NZ SeaRise programme, which will this year release location-specific sea-level rise projections for the entire coast of New Zealand.