Thanks to a new data management and analytics programme, New Zealanders will be able to see how much and how fast sea levels will rise along their stretch of coast and in their neighbourhood.
The NZ SeaRise: Te Tai Pari O Aotearoa programme developed by Takiwa, a data management and analytics platform, has announced that it will release location-specific sea level rise projections out to the year 2300 for every 2km of the coast of New Zealand.
Co-leaders of the programme, Dr Richard Levy, from GNS Science and Professor Tim Naish from Te Herenga Waka: Victoria University of Wellington, say climate change and warming temperatures are causing sea levels to rise, on average, by 3.5mm per year.
This rise is being caused by thermal expansion of the ocean, by melting land-based glaciers, and by melting of the Greenland and Antarctic ice sheets.
However, they say local sea level rise around the coast of New Zealand is also affected by up and down movements of the land.
“We are very aware when these vertical land movements occur in large jumps during earthquakes, but less obvious to us all is that smaller shifts occur continuously in between large seismic events,” they say.
These small but continuous changes add up, and in areas that are going down (subsiding) the annual rate of sea level rise can double.
“We have connected this vertical land movement (VLM) data with climate driven sea level rise to provide locally-relevant sea level projections.
“Property owners, councils, infrastructure providers and others need to know how sea level will change in the coming decades so that they can consider how risks associated with flooding, erosion and rising groundwater will shift,” Levy says.
“Twenty years ago we thought sea level rise was like pouring water into a bathtub — if you put more water in, it rises uniformly around the world. But it’s much more complicated,” Naish says.
The NZ SeaRise projections tool will allow users to click on a particular location on the coast and see how much sea level is expected to rise, and by when, under different climate change scenarios.
“We have estimated future sea-levels for 7434 sites around our coastline. The largest increases in sea levels will occur along the southeast North Island along the Wairarapa coast,” Levy says.
“Here, land subsidence rates are high, and sea level could rise by well over one and a half metres by 2100 if we follow the least optimistic climate change scenario.
“In contrast, land is rising near Pikowai in the Bay of Plenty, and uplift rates may keep pace with climate change-driven sea level rise, causing a small fall in sea level if we follow the most optimistic climate scenario.”
Based on current international emissions reduction policies, global sea levels are expected to rise about 0.6m by 2100.
“However, for large parts of New Zealand this will double to about 1.2m due to ongoing land subsidence. We have less time to act than we thought,” Naish says.
“We know that global sea level rise of 25 to 30cm by 2060 is baked in and unavoidable, regardless of our future emissions pathway,” Levy says.
“But what may be a real surprise to people is that for many of our most populated regions, such as Auckland and Wellington, this unavoidable rise is happening faster than we thought.
“Vertical land movements mean that these changes in sea level may happen 20 to 30 years sooner than previously expected.
“For many parts of New Zealand’s coast, 3cm of sea level rise is a threshold for extreme flooding, above which the 100-year coastal storm becomes an annual event.”
Sea level rise projections for the entire coastline will allow better decision-making about how to adapt to rising seas. The new projections are being incorporated into the next Ministry for the Environment guidance for local government practitioners on coastal hazards and climate change.
“With the recent release of the Government’s draft National Plan on Climate Adaptation, the timing couldn’t be better, as the impacts and risks of sea level rise are poorly defined for large parts of the coastline,” Levy says.
“We expect councils and planners will be the primary users. The finance and insurance sectors have already been asking for the data — in part driven by the Task Force on Climate Related Financial Disclosures reporting requirements that need to be met by 2024.”
Sea level rise can be kept to a minimum by enacting policies to meet Paris Agreement targets to limit global warming by 2100 to between 1.5° to 2°C.
“The severity with which we will experience sea level rise, and other impacts of climate change, can be lessened if we do all we can to limit warming by reducing emissions now. The sooner we act, the more effective that action will be,” Naish says.
“To be forewarned is to be forearmed, and this new science gives us the time and opportunity to put in place equitable and effective adaptation measures that will limit the impact of unavoidable sea level rise for the people of Aotearoa.”
NZ SeaRise is a five-year research programme funded by the MBIE’s Endeavour Fund. It brings together 30 local and international experts from Te Herenga Waka-Victoria University of Wellington, GNS Science, NIWA, University of Otago, and the Antarctic Science Platform to improve projections of sea level rise in New Zealand. To find out more, visit www.searise.nz.
New climate change report a reality check
The Intergovernmental Panel on Climate Change’s (IPCC) Working Group III has released its mitigation report titled Climate Change 2022: Mitigation of Climate Change.
Infrastructure New Zealand says the group’s findings make for a sobering read. At current global mitigation policy settings, greenhouse gas (GHG) emissions are likely to exceed 1.5°C this century.
Without substantially strengthening policies beyond those already in place internationally, we are likely to see a median increase of 3.2°C on pre-industrial levels, by 2100. If we are to limit warming to 2°C, a rapid acceleration of mitigation efforts is needed.
The building, transport and energy sectors received significant attention in the report.
Globally, the built environment contributes 40% of emissions, so is central to any chance of limiting warming.
In New Zealand, emissions from construction have jumped 66% in the past decade, and represent 20% of the country’s total emissions.
The authors caution that unambitious policies will lock in carbon-emitting construction processes, and curtail the potential benefits of effectively implemented mitigation and adaptation interventions.
