Disagreement over Dunedin sea level predictions

Professor Jim Flynn has provoked some discussion after making some radical predictions about potential rapid sea level rises in South Dunedin and the rest of the low lying parts of the city.

These predictions have been disputed by other academics.

ODT: Flynn’s sea level figures disputed

Associate Prof Nicolas Cullen and senior lecturer Daniel Kingston have described the predictions by Jim Flynn as “very unlikely”.

On Monday, Prof Flynn told a Dunedin City Council public forum huge erosion of polar ice that had begun in 2014 meant predictions on the rate of climate change had changed.

He said there were 1932 homes in Dunedin, mainly in South Dunedin, built below 25cm, and a 25cm sea-level rise could occur before 2034.

He said by 2090, South Dunedin would be under 5m of water, along with Forsyth Barr Stadium, the Otago Polytechnic and other low-lying areas.

That’s fairly extreme. Many would claim bonkers, with some justification.

…approached for comment on the predictions, Prof Cullen and Dr Kingston disagreed.

Prof Cullen, whose expertise includes glaciology and climate change, said Prof Flynn’s figures were “questionable”.

He said the observed sea-level rise was 3.4mm a year, which was “quite high compared to historical estimates”.

If that rate continued for the next 20 years, there would be a total 68mm sea-level rise – “quite different”from Prof Flynn’s estimate.

“I agree that there is evidence that the two large ice sheets [Greenland and the Antarctic] may contribute more to sea-level rise in the future than previously thought, but I would think it is very unlikely that South Dunedin will be under 5m of water in 2090.”

Dr Kingston, whose expertise includes atmospheric circulation patterns and climate change, said he agreed with Prof Cullen.

“The numbers in that article, like 5m by 2090, are at the very, very extreme end of what’s likely.”

To Prof Flynn’s suggestion the more recent erosion of polar ice had changed what could be expected in terms of sea-level rise, Dr Kingston said, “I don’t think the matter is settled by any means.”

A rise of 5m would mean the entire West Antarctic ice sheet disappearing, or the entire Greenland ice sheet disappearing.

“The likelihood of that happening by the end of the century is low – not impossible – but the real extreme end of the situation.”

Flynn’s claims may cause some concern. Things like insurance cover and resale values of low lying properties won’t be helped by worst case scenarios being portrayed as likely.

I’m at 100, so way out of the danger zone but even a half metre rise would cause significant problems in the drained wetlands of South Dunedin where flooding cause major problems in 2015.

Jim Flynn can be a very interesting dude but he isn’t helping anyone with worst case claims that amount to scaremongering, but perhaps his aim was to attract attention to a real potential problem with a bit of exaggeration.

The problem is that claims like this are easy to dismiss as nuts.