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 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.
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As for the Ministry projections on sea-level rise themselves – they are already out of date and are very conservative compared to the latest report from the US Oceanic and Atmospheric Administration (NOAA).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
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
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 …….
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.
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)
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 –