A University of Otago professor is concerned thousands in south Dunedin are at risk of being swallowed by rising sea levels by 2034.
But while the sea level rise is a serious risk, two other scientists are concerned his calendar will cause unnecessary panic.
Professor Jim Flynn, an Emeritus Professor in Politics at Otago University, told Dunedin City Council in a presentation that around 2000 houses in south Dunedin will be claimed by rising sea levels by 2034.
In both the presentation and during a later conversation with Newshub, he said previous predictions failed to account for the melting of the Greenland ice sheet.
"Imagine a bathtub - if the water is too high at one end, and someone pours a pail of water in at one end, you think, 'Oh I think I'll pump this down to the south end of my bathtub'," he told Newshub.
"But it's all on a level. When these homes in south Dunedin are at sea level, when you get ground water in them, you can't pump it into the ocean because the ocean is at the same level as your floor."
Prof Flynn said sea level rise is increasing over time and is almost at 1cm a year, with 2015 rising by 0.86cm and 2014 by 0.75cm, citing NASA data.
However Newshub was unable to verify this claim, with NASA's website citing the current rise is at a rate of 3.4mm a year - significantly less than Prof Flynn says.
With 1900 houses within 25cm of the sea level in south Dunedin, he predicted the sea would rise 30cm by 2034 and drown them.
Claim a few decades off - scientists
But he isn't getting much support from other scientists.
Dr James Renwick and Professor Tim Naish, both from Victoria University and specialising in climate change, aren't particularly confident in Prof Flynn's predictions.
"He's right to be raising the issue as a real concern but I have a little bit of concern that his numbers are slightly on the high side, or very much on the high side," Prof Naish told Newshub.
Instead he said the 30cm rise globally would be more likely to be reached by 2050-60 - still near enough to be concerned, but not as frantic as Prof Flynn said.
"That's already locked into the system from the climate change that's happened already," Prof Naish said.
"[Prof Flynn's claims are] well above where mainstream science is at the moment. But that's not to say he's wrong for trying to raise public awareness about it, I think we just have to be careful with the numbers at the moment."
We could potentially be looking at a 2m rise by 2100, which would cause catastrophic damage to coastal regions, Prof Naish says.
While Dr Renwick agreed with Prof Naish, he was even more cautious about the timeframe.
"I'd say it's still towards the upper end for this century, but somewhere between 1m and 2m is quite possible unless we bring emissions down quickly and go to zero within 40-odd years from now," he told Newshub.
"I haven't spoken to Prof Flynn but I don't know where he's getting his information from, but I think he's got the wrong end of the stick about this increase in sea level rise - it hasn't happened, as far as I'm aware."
'A new measure of alarm is in order'
Prof Flynn dismissed the other scientists' concerns when Newshub raised them to him.
"Let [Prof Naish] think what he wants. In five years he's going to get his feet wet. He can hang onto that," he said.
"He and I have made our predictions, let us stand by them and see who's right."
Prof Flynn said any studies prior to 2015 were "obsolete", including the Government report Dr Renwick and Prof Naish led, as they didn't account for the melting of the Greenland ice sheet.
"A new measure of alarm is in order."
Prof Naish and Dr Renwick aren't as keen to call for panic.
"What he talks about may be the future but it's a fair way off yet," Dr Renwick said.
"That's not to say he's wrong for trying to raise public awareness about it, I think we just have to be careful with the numbers at the moment," Prof Naish said.
Dunedin City Council and the Otago Regional Council announced a joint programme to develop options dealing with rising groundwater in south Dunedin at the beginning of the month.
It includes contracting a report from environmental specialists Golder Associates.
"We are at the beginning of a long term project to plan for climate change. Once we have a lot of this technical information together, we will be able to discuss next steps with the community," says Dr Laura McElhone, DCC group manager of water and waste.
"To help us with this overall project, we want to have a better understanding of how communities elsewhere in the world have managed the challenge of rising groundwater, particularly in areas that have similar social, economic and environmental settings to south Dunedin."
South Dunedin is threatened by more than just the rising sea - it's also begun subsiding, according to a report published last year.
It means there's a very real concern in the next few decades, resident won't be able to call it home anymore.
Newshub.
