Blunder – Mistaken Reveal of Government’s Latest (Already Outdated) Sea-Level Rise Projections

The latest all-important Ministry for the Environment Guidelines for Local Authorities on Climate Change have been prepared in strict secrecy.  They are held under a tight embargo until the Minister gives his approval for their official release. But key elements of the guidelines, including the latest Ministry projections for sea-level rise have mistakenly been made public in a PowerPoint presentation by the Ministry recently given to the Waikato Natural Hazards Forum.  The Forum published the slides on the Forum’s public website, from where I was able to download a copy of the presentation.  The Minister Nick Smith will likely be thoroughly pissed off about this breach of information security – the projections were meant to be hush hush until he made his grand announcement.

The presentation not only includes crucial details of the Government’s projections of sea-level rise but also describes levels of sea level rise which should be applied by local authorities to various types of development. 

 

Slide 11 contains 4 scenarios based on the Ministry’s projections out to 2120 for New Zealand sea-level rise.  These coincide with 3 IPPC climate change based scenarios plus an additional H+ scenario said to be at the upper end of projections.

Slide 11

Slide 12 sets out single sea-level rise values derived from the scenarios relating to 3 broad categories of development which are assigned 3 different sea-level rise allowances. These “minimum transitional sea-level values” are provided to assist councils in the short term.  

Slide 12

 

Category A  – Slide 12 describes how major new development or intensification of existing developments needs to consider a high-level sea-level rise value of 1.9 m.  This 1.9 m value would also apply to new infrastructure such as roads or infrasructure having the potential to be staged.

Category B is given a sea-level rise minimum transitional value of 1 m and relates to land use planning controls for existing coastal development and asset planning. This single value is to be used at a local/District scale transition until “dynamic adaptive pathway planning is undertaken”

Category C has a value of 0.65 m for “non-habitable short-lived assets with a functional need to be at the coast and either low-consequences or readily adaptable (including services)”

As for the Ministry projections on sea-level rise themselves – they are already out of date and are very conservative compared to the latest report from the US Oceanic and Atmospheric Administration (NOAA).  NOOA states that a plausible upper range scenario for SLR by  2100 is 2.5 m  and its midrange projections are between 1.5 m and 2.0 m

NOOA Projections SLR 2.5m by 2100

 

These are the projections metres for the various scenarios. Taking the Intermediate-High scenario at 2050 for example shows a sea level rise of 0.44 m

NOAA SLR to 2200HL

What could my town of Thames look like in 2050 – just 33 years away – with 0.44m of sea level rise and a normal maximum tide? (Blue areas are connected to sea and green areas disconnected from sea –  Map generated by Waikato Regional Council Coastal Inundation Tool)       Like this …….

Thames Normal Tide 0.5m slr

The Parliamentary Commissioner has warned that current 1-in-100 (1% AEP) severe damaging storm tide events will occur every year with 0.5 m of sea level rise.

half M rise ann event Parl Comm

 

This is what Thames will look like every year with a mid-range storm tide  and 0.5 m of sea level rise – (Note: not worst case storm tide)

Thames Storm surge median .5m 3.2

With 1.0 m of sea level rise and a mid-range storm tide, with a NOOA Intermediate-High projection – by 2080 you have Thames looking like this every day

Thames 3.7 storm tide 0.1mslr

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4 thoughts on “Blunder – Mistaken Reveal of Government’s Latest (Already Outdated) Sea-Level Rise Projections

  1. Presumably, at some point, we should see a rapid acceleration of SLR in NZ for these projections to be plausible. We don’t have any acceleration in tide gauge records at present

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  2. Two things.

    Risk is likelihood times consequences. The consequences of sea level rise is ultimately a wipe out, but it is slow coming so property owners can see what’s coming and plan accordingly. It isn’t like many other risk where we don’t have that luxury.

    But more important is the “likelihood” bit of the equation.

    Table 4 of the NOAA report is the one that helps us. It shows the likelihood of the sea level rises occurring on various scenarios. RCP4.5 is the likely one so 1m by 2100 is very unlikely (3%). Note this isn’t 3% next year, it is 3% once we get to the turn of the century, and even then that’s just someones projection.

    The answer is that property owners should be encourage to keep an eye on what’s happening if they are planning on spending up large, but should TLAs get into the business of preventing development? There’s a lot of enjoyment that can be had in 83 years. I can just see TLAs saying new born babies this year can’t spend anything on their development because they’ll be dead by 2100.

    The other point is technical. The PCE was wrong in saying that current 1-in-100 (1% AEP) severe damaging storm tide events will occur every year with 0.5 m of sea level rise. 1% AEP events will still only occur every 100 years, they will just happen .5 m higher. Thames will only look like your pictures every 100 years and then it needs to be weighted by the likelihood associated with the projection.

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    1. On the PCE 1-in-100 issue the report is saying the equivalent force and intensity of a CURRENT 1% AEP will occur every year with 0.5 m of SLR . Thames has a sea wall breached during Drena 1996 causing $ millions of damage. Such events will be annual events approx with 0.5 m SLR

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