Dunedin to be flooded

The ODT alarms:

Dunedin could face some stark choices by the end of the century, with sea-level rise expected to force either the retreat from, or complete evacuation of, South Dunedin, St Kilda and St Clair.

Dunedin will just be one giant swimming pool!

A report on climate change and its effect on Dunedin includes a prediction of an upper level for sea-level rise of 1.6m by 2090.

Okay that is 1600 mm over 80 years which is an average rise of 20 mm a year.

Predicting the upper range for sea-level rise was also “problematic”, he said, with the most recent Intergovernmental Panel on Climate Change (IPCC) suggesting 0.6m, but more recent research suggesting 1.6m was a more prudent prediction.

I prefer to wait for the to update their report, rather than have people cherry pick individual more alarmist pieces of research.

The report said that the likely increase in levels was 180 to 590 mm, which is an average rise of 1.8 to 5.9 mm a year – between one tenth and one third of what the story reports.

So how likely is a sea level rise of a massive 20 mm a year?

What has been the rise so far in NZ?

Consequently, sea levels around New Zealand have risen on average 1.8 mm/year over the last 40 years with the total sea level rise over the last century of 0.17 m.

So the rise over the last 100 years has been 1.7 mm a year and last 40 years has been 1.8 mm a year. So that is 10% of the 20 mm Dunedin will be flooded scaremongering.

Now in the last 17 years, sea level rises have been greater – an average 3.1 mm a year. That is consistent with the 590 mm increase, but still a long way off the 1600 mm talked about in the article.

Also one has to understand that to get an average of 20 mm a year over 80 years, you need quite massive increases in the latter section to make up for the current slower rises.

If you assume a linear increase in the average annual rise, then the amount of annual rise has to increase by 0.45 mm a year. What means is that by 2020 the rise will be 7 mm/yr, by 2030 12 mm/yr and by 2090 it would be 39 mm/yr.

Is anyone willing to bet money that by 2020 the average sea level rise will be 7 mm/yr?

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