Study highlights the need to bust public myths about sea-level rise

Overestimating the scale and rate can result in feeling anxious and helpless, rather than being motivated to mitigate and adapt, say researchers.

Many New Zealanders overestimate current and projected sea-level rise and the rate at which it is occurring, and misunderstand what causes it, according to a newly released study by researchers at Te Herenga Waka—Victoria University of Wellington and Te Whare Wānanga o Waitako—University of Waikato.

The study, conducted by the Te Herenga Waka-hosted NZ SeaRise programme and published in PLOS ONE, highlights the need to better communicate the actual scale and rate of sea-level rise, says lead researcher Associate Professor Rebecca Priestley from the University’s Te Wāhanga Pūtaiao—Centre for Science in Society.

Associate Professor Priestley says focusing on extreme and often unsound projections of sea-level rise can result in public anxiety and feelings of helplessness, rather than motivating people to take action to mitigate and adapt.

She and her study colleagues, Zoë Heine, a PhD candidate in the Centre for Science in Society, and Associate Professor Taciano Milfont, Reader in Environmental Psychology at the University of Waikato, write that: “While there are obvious dangers associated with a public that underestimates or minimises the dangers of sea-level rise—such as not taking adaptation measures, or not supporting governments committed to mitigation and adaptation—there are also dangers associated with a public that overestimates sea-level rise.”

Average global sea level has risen by more than 16cm since 1900, but many of the surveyed adult New Zealanders either underestimated (38.2 percent) or overestimated (35 percent) the amount.

A significant group (18.9 percent) overestimated global sea-level rise projections to 2100, while 74.4 percent were in line with scientifically plausible projections, selecting ‘up to 40cm’ (28.6 percent), ‘up to 1m’ (30.9 percent) and ‘up to 2m’ (14.9 percent).

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 overestimated (38.9 percent), selecting ‘about 120m’ (17 percent), ‘about 240m’ (10.9 percent) and ‘more than 500m’ (11 percent). The next largest group (38.8 percent) underestimated, selecting ‘about 30m’, while 22.3 percent selected ‘about 60m’, a figure broadly in line with scientific estimates.

Respondents were asked the fastest period the above scenario could occur. While scientists suggest it is under a sustained warming climate over thousands of years, only 11.6 percent were in line with this. Of the rest, 33.1 percent selected ‘decades’ and 39 percent selected ‘centuries’.

Asked to identify and rank the major causes of sea-level rise from a 10-item list, 28.7 percent 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,” write the researchers.

“For example, 6.8 percent 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 percent 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.”

Associate Professor Priestley, who in 2016 won the Prime Minister’s Science Communication Prize, says Aotearoa New Zealand needs to be talking about sea-level rise as a country, and at regional and community levels, and we need good scientific information to enable this.

“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 says.

“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.”

Later this year, NZ SeaRise will release location-specific sea-level rise projections for the entire coast of New Zealand, taking into account vertical land movement as well as updated global sea-level rise data from the Intergovernmental Panel on Climate Change’s Sixth Assessment Report.

Associate Professor Priestley and colleagues have written an article about their findings for The Conversation and it is available for free republication.