Data should be a tipping point for us

The true realisation of what global warming will do to New Zealand should be sinking in. Subsiding land and rising oceans could push sea levels in our two biggest cities and many other parts of the country to double that generally projected — far sooner than we thought.

The NZ Searise programme has factored the role of undulating land movements into calculations for rising sea levels and, as a result, the projections change dramatically for places such as Wellington, Auckland, Napier, and Marlborough/Nelson.

As anyone who has lived in New Zealand long enough to feel a decent earthquake knows, this island country moves, sometimes in large shifts. The Searise scientists calculated the longer impacts of smaller and larger seismic events and found subsidence in many parts of New Zealand could double the effect of a rising sea level.

Co-leader of the programme, Professor Tim Naish of Victoria University, says sea level rises mean some parts of New Zealand could be inundated by twice the global average. International climate commitments anticipate global oceans to climb by about 60cm before this century’s end. “However, for large parts of Aotearoa, this will double to about 1.2m due to ongoing land subsidence.”

The data has been built into a website, showing location-specific sea level rise predictions to the year 2300, for every 2km of the New Zealand coast. Shortly after going live, the website was shut down, allegedly by cyber attack, although massive interest was also understandable.

The consensus has it that climate change and warming temperatures are causing sea level to rise, on average, by 3.5mm a year.

In a rational world, the research would inform zoning decisions and steer development away from the more prone sites. However, under the Resource Management Act, councils cannot prevent people from building on private land. Insurance will become increasingly prohibitive.

Naish says once-in-a-century floods could be occurring annually in 20 years. It is not only homes at risk, it’s water infrastructure, wastewater treatment, power and roads.

NZ Searise was set up with an $8m government grant in 2017 to discern accurate estimates of the magnitude and rate of sea-level rise for our coastal regions to the century’s end.

Projections from the programme have caused pockets of concern which often ebbed away as other priorities arose.

The inclusion of land movement projections has provided a whole new picture.

Could this be the point where the majority sit up and take notice of the sea change about to crash over us? It’s to be hoped so.