0.5-2.0 metre sea level rise possible, more frequent floods

A ‘best case’ scenario of an average 0.5 metre sea level rise, with far more frequent extreme coastal water levels, would caause a lot of problems. A ‘worst case’ scenario is an average 2 metre rise, equivalent to ‘100 year floods’ every day. If scientists are wrong it could be less – or more.

Noted:  The impact rising sea levels will have on New Zealand

Under present projections, the sea level around New Zealand is expected to rise between 30cm and 1m this century as warming ocean waters expand, mountain glaciers retreat and polar ice sheets in Greenland and Antarctica shrink. Even if global emissions were to stop today, more warming over the next few decades is inevitable, bringing a trail of storms, ocean surges, flooding and erosion.

The Ministry for the Environment says extreme coastal water levels, currently expected to be reached or exceeded once every 100 years, will, by 2050-2070, occur on average at least once a year.

Evidence is already piling up. Waihi Beach in the Bay of Plenty, Beach Road south of Ōamaru, and small seaside towns in Taranaki and the West Coast  all bear the signs of coastal erosion. Low-lying areas in Napier, Whakatane, Tauranga, Motueka, Nelson, parts of Auckland and Wellington have all been inundated by storms.

Just before Christmas, the Whakatane District Council declared 34 properties in Matata in the Bay of Plenty “unliveable” due to severe flooding risk.

“We are a coastal nation so we are going to get whacked by sea-level rise,” says GNS climate scientist Tim Naish, head of a new Government-funded programme set up to assess the magnitude and rate of sea-level rise. “We’re talking places we will not be able to live in because a so-called one-in-100-year flooding event becomes a daily event.”

Worst-case scenario, he says, is an average 2m sea-level rise by the end of the century. Best-case scenario, if we achieve the goals of the Paris climate agreement and keep temperature rise well below 2°C, is 50cm of sea-level rise.

A 2 metre rise would cause major problems for a large part of Dunedin, the reclaimed South Dunedin area. It would also stuff the Portobello road, parts of the road to Port Chalmers (which links the city and Otago province to the port) and also the road to Aramoana.

Stuff:  Coastal hazards report warns sea-level rises a ‘slowly unfolding red-zone’

The threat of rising sea levels has been likened to a “slowly unfolding red-zone” as a major Parliamentary report warns thousands of homes could become uninhabitable.

Environment Commissioner Dr Jan Wright released her national report on coastal hazards on Thursday, recommending a major overhaul of the way New Zealand prepared for coastal erosion and rising sea-levels.

She found Christchurch and Dunedin would be the cities most affected by future sea-level rises, resulting in potential damage costing billions of dollars.

In Christchurch, nearly 10,000 homes and 200 kilometres of road were less than 1.5 metres above the spring high tide mark, more than Auckland and Wellington combined.

Dunedin mayor Dave Cull said the report showed the city would likely be the “most extensively affected” by coastal hazards.

“We have an exceptionally large number of homes at risk, as well as infrastructure.”

The report found nearly 2700 homes, mostly in South Dunedin, were less than 50cm above the spring high tide mark.

This already impacts on many property values. Anything like a 2 metre average rise would also impact significantly on Mosgiel and the Taieri Plain, where floods are already common. The Momona airport runway would go under.

But we always have the option of arguing that nothing adverse will happen and doing nothing is fine.


  1. Gerrit

     /  October 23, 2018

    Surely then time to look and learn from the Dutch and start building dykes.

  2. Alan Wilkinson

     /  October 23, 2018

    0.5-2m sea level rise by when?

    Current global rate is 3mm/yr which would take 170 years to reach 0.5m and 670 years to reach 2m.

    Has simple common sense become entirely obsolete?

    • Griff.

       /  October 23, 2018

      Yess Alan
      Of course rather than your opinion we have actual published science to inform us.
      Climate-change–driven accelerated sea-level rise detected in the altimeter era


      Satellite altimetry has shown that global mean sea level has been rising at a rate of ∼3 ± 0.4 mm/y since 1993. Using the altimeter record coupled with careful consideration of interannual and decadal variability as well as potential instrument errors, we show that this rate is accelerating at 0.084 ± 0.025 mm/y2, which agrees well with climate model projections. If sea level continues to change at this rate and acceleration, sea-level rise by 2100 (∼65 cm) will be more than double the amount if the rate was constant at 3 mm/y.

      We can also look at what is being measured at the poles .

      Your ignorance is not common sense it is denial. You reject reality because it gets in the way of your ideology .

      • Gerrit

         /  October 23, 2018

        As soon as one reads

        …careful consideration of interannual and decadal variability as well as potential instrument errors</blockquote)

        we understand that the data was manipulated. Was the data manipulated to show a predetermined outcome?

        Problem is steering a course away from the blame game and onto preventative measures such as building defenses.

        Where is the political will and the tax payers funding? Loads of teeth gnashing and hand wringing, not much in the way of positive preventative measures.

        Simple question, if all carbon emissions were stopped overnight, at what time can we expect a drop in ocean levels?

        Or will ocean levels rise irrespective and the need for physical defenses become paramount?

      • Alan Wilkinson

         /  October 23, 2018

        No, Griff, I’m just expecting officialdom to use elementary common sense towards the issue.

        Supposing your acceleration is accurate and persists then by your own estimate it will take some 80 years to reach the lower level of the range PG is posting about.

        That is ample time to adapt supposing counter measures have not become available and been taken. Let’s hear it for common sense.

        • Griff.

           /  October 23, 2018

          No Alan
          You dont have common sense as pointed out by debunking your liner growth and ignoring of the acceleration in the trend.
          You dont want to do anything because it might cost you.
          Your greed is not common sense its naked self interest.

          • Alan Wilkinson

             /  October 23, 2018

            The acceleration is still speculative because of the short timespan of the available data as shown by the large estimate of the uncertainty (which is almost certainly underestimated).

            Even so, the predicted rate of sea level rise is moderate and not alarming. We have time to adapt and respond.

            • Griff.

               /  October 23, 2018

              Alan in case you did not notice i not only posted the present rise and projected acceleration I included the fuckin melt from the Antarctic
              That is also accelerating at significant rate .
              That sea level rise is happening at an accelerating pace is certain Because melting ice and warming oceans are being measured .

              We will be facing this problem for the next millennium.
              Plenty of time to adapt I am sure because the alternative is called drowning .

              But meantime building infrastructure with a fifty year life span must included the projection of rise to a reasonable level of risk .
              That means 1 meter of rise minimum over fifty years.
              At that level You can kiss goodbye to a hell of a lot of coastal development including parts of Auckland’s motorway system and some very exclusive coastal property . It is not just sea level it is also storm serge and flooding from extreme rainfall both of which are also expected to increase.

              We need to start looking at what is at risk and how we minimize that risk going forward or we will end up paying more in the long run.
              Because you can bet your last dollar if we dont people like you will be demanding that ratepayers pick up the tab.

      • Griff.

         /  October 23, 2018

        Oh dear
        They tell me you tutor math Maggy.
        Do tell us why you think the liner trend over 120 years shows that sea level rise has not accelerated recently?

        However, the extent to which the limitations of tide gauge analyses have affected estimates of the GMSL rate of change is unclear. Here we revisit estimates of twentieth-century GMSL rise using probabilistic techniques9,10 and find a rate of GMSL rise from 1901 to 1990 of 1.2 ± 0.2 millimetres per year (90% confidence interval). Based on individual contributions tabulated in the Fifth Assessment Report7 of the Intergovernmental Panel on Climate Change, this estimate closes the twentieth-century sea-level budget. Our analysis, which combines tide gauge records with physics-based and model-derived geometries of the various contributing signals, also indicates that GMSL rose at a rate of 3.0 ± 0.7 millimetres per year between 1993 and 2010, consistent with prior estimates from tide gauge records4. The increase in rate relative to the 1901–90 trend is accordingly larger than previously thought; this revision may affect some projections11 of future sea-level rise.

        For someone with a PhD you do post some really dumb shite .

        • Maggy Wassilieff

           /  October 23, 2018

          They tell me you tutor math Maggy.

          Do they?

          • Griff.

             /  October 23, 2018

            you gotta laugh .
            If you link to a linear trend it says nothing about if the rate is accelerating .
            It is by definition the average rate of rise over the entire record.

            Church and white tidal gauge to 2014 linear trend.

            modified lowess smooth:

            Actual rate of change


            You accuse me of not understanding but its you who cant even get basic math concepts .

            • Maggy Wassilieff

               /  October 23, 2018

              I assume you can interpret v/t graphs. Have a look at what that last graph is doing around 2000 and thereafter.
              Acceleration is given by the slope of a v/t graph…The slope is decreasing after 2000 – looks like the rate of sea-level rise is decelerating after 2000.

              Wonder what caused the acceleration in sea-level rise from 1922-1938?
              Practically the same as 1985 – 2000.

  3. Zedd

     /  October 23, 2018

    Im guessing those who live on property above 2 meters (above current high tide levels) are not concerned or are just C-C deniers.

    Ice free arctic (sea ice).. coming soon
    loss of glaciers… happening NOW
    diminishing ice shelves in antarctica… happening NOW

    BUT.. where is the ‘evidence’ folks ?
    The TRUTH is out there folks.. if you actually look, rather than just ignore 😦

    btw; I heard recently that one of the biggest financial sponsors of ‘C-C denial research’ is.. wait for it.. EXXON !

    • Alan Wilkinson

       /  October 23, 2018

      You’ve taken a long time to tap into your alarmist echo chamber, Zedd? They’ve been claiming that for a decade or two.

      • Zedd

         /  October 23, 2018

        ‘You’ve taken a long time to tap into your alarmist echo chamber, Zedd?’ sez AW

        Ive been writing it on YNZ.. since I first came here. There maybe ‘extremist views’ on both sides, but ignoring or denying ‘the reality’ of the issue, (hoping it will just go away) is just like.. “CRAZY MAN !”

        • Alan Wilkinson

           /  October 23, 2018

          Have you been saying since you first came here that you heard recently that EXXON is sponsoring climate denial?

    • The Consultant

       /  October 23, 2018

      Im guessing those who live on property above 2 meters (above current high tide levels) are not concerned or are just C-C deniers.

      From a pragmatic perspective there’s no difference between “not concerned” and “C-C deniers”. Either way it’s more than a guess but is likely quite true that most of those who will be hurt by $5 or $10/litre (or higher) petrol costs and other increased fossil fuel costs needed to reduce their use to zero, are indeed people who don’t have lovely homes on the coast, like South Aucklanders.

      For the likes of South Dunedin – also solid Labour voters – it will be an interesting scenario: pay vastly more for fossil fuels and still get flooded out because we’re at the mercy of China, India and other developing countries. Even by the IPCC/Paris agreement standards I don’t think that works as an insurance policy, which may be why people are tuning this out when they vote – although they will vote on $10/litre petrol. 🙂

      What’s really frightening is that Exxon and others have such incredible control over so many countries, including many communist countries, that have contributed to the increase in annual global CO2 emission tonnage since the mid-70’s. Must be all those oil burning power stations as I don’t think Big Oil owns any coal mines.

      The good news is that all the countries who signed up to the Paris Agreement have pledged that their emissions will reduce after they’ve reached peak emissions!!!!! And apparently meeting the targets they’ve agreed to will limit the 2100 temp increase to 2.8C. Apparently there’s a lot of bad news about even a 2C increase so I guess the IPCC is also realising that we’re stuck between a rock and a rising tide.

      • Griff.

         /  October 23, 2018

        That such nonsense gets up ticked shows how disconnected from reality some on here are.


        Either way it’s more than a guess but is likely quite true that most of those who will be hurt by $5 or $10/litre (or higher) petrol costs

        Burning 1 L of gasoline produces approximately 2.3 kg of CO2.
        To have a price component from the ETS of five dollars a liter in petrol would mean paying over $2100 a tonne For CO2 emissions
        The highest I have ever seen suggested is $100 a tonne…. its presently $25 .

        Even by the IPCC/Paris agreement standards I don’t think that works as an insurance policy,

        The IPCC is the organization that gives our best understanding the science behind climate change
        It has nothing to do with the negotiation of goverment policy’s like the Paris agreement that is the UNFCCC.

        Your opinion is devoid of any actual knowledge about what you are talking about .

        • The Consultant

           /  October 23, 2018

          The highest I have ever seen suggested is $100 a tonne…. its presently $25

          In that case fossil fuels will continue to be burned, which means the zero emission target will remain beyond reach for a period far beyond the supposed drop-dead dates.

          It has nothing to do with the negotiation of goverment policy’s like the Paris agreement that is the UNFCCC.

          A distinction without a difference. No IPCC. No Kyoto, Copenhagen, or Paris treaties or “agreements”, all of which take their guidelines on negotiating CO2 emission reductions from the various emission production scenarios produced as part of each IPCC report. Not to mention national screamfests from individual political parties which demand policies like increased fossil fuel taxes, “green” energy subsidies, market manipulations and a host of other stuff on the basis of …..
          …. the IPCC science forecasts.

          In any case, the truest of True Believers in Thermogeddon understand exactly what’s required, which is why they leaped all over the latest report screaming about how capitalism needed to be finished off for good or Humanity Will Be Destroyed – or something, something. Long may they scream!

          Fortunately the vast majority just ignore this and keep on keeping on – admittedly with ever higher costs that don’t achieve anything, but that’s still a better scenario than the anti-capitalists fondest hopes.

  4. The Consultant

     /  October 23, 2018

    Just in case people don’t want to click, that last one is a doozy:

    “In the USA more people are going to die .
    I hope this fucker hits Miami dead center and wipes it off the map .”

    Not unhinged at all! 🙂

  5. Maggy Wassilieff

     /  October 23, 2018

    Looks like these chaps aren’t too bothered about sea-level rise in the vicinity of Auckland Harbour

  6. chrism56

     /  October 23, 2018

    This post is about sea level rise in New Zealand. There are three ports in the records that have long term sea level data and have 2016 records. They are Dunedin, Port Taranaki and Wellington . Here is Dunedin’s https://tidesandcurrents.noaa.gov/sltrends/sltrends_station.shtml?id=690-032
    Despite all the assertions of Griff and the satellite altimetry, the tide data shows NO acceleration, just a linear trend going back about 100 years. The same trend is there for ports around the world (Freemantle, New York) , except where there is localized subsidence from ground water pumping, like Houston. This discrepancy between satellite and tidal records is glossed in the literature. If the concern is flooding, then it is the tidal data that is the critical one.

    All indications are that there will be about a 20cm rise in the sea level at Dunedin by 2100.
    The rainfall data for NZ also shows no overall trends. https://statisticsnz.shinyapps.io/seasonal_rainfall/
    Even places that have changed, the scatter is greater than the trend.
    It is scare tactics without the data (not some model’s output) to back it up.

  7. chrism56

     /  October 23, 2018

    And here are the trends for rainfall intensity
    Note the summary
    For the majority of locations around New Zealand, there is no clear evidence that intense rainfall events changed between 1960 and 2016. However, intense rainfall increased at some sites and decreased at others.
    Between 1960 and 2016 at the 95 percent confidence level:
    The proportion of annual rainfall occurring in intense events (in the 95th percentile) decreased at 4 of 30 sites (Auckland, New Plymouth, Rotorua and Taupō) and increased at two (Napier and Timaru).
    Annual maximum one-day rainfall amounts decreased at 4 of 30 sites (Auckland, Hamilton, New Plymouth and Taupō) and increased at two (Dunedin and Timaru).
    Decreasing trends in both measures of intense rainfall have been found at sites located in the northern and central North Island.
    So rainfall is not getting worse (As they are doing LMS, the data for Dunedin is skewed by one heavy rain in 2015 – the one in 1980 doesn’t tilt the line).
    Another alarmist myth

    • Griff.

       /  October 23, 2018

      hello chrism56
      Did you actually do anything beside look at the liner trend over the entire record ?
      no ….
      Sorry mate linking to a linear trend over the entire record shows nothing but that you dont understand acceleration.
      lets see what the sea level experts say.
      The increasing rate of global mean sea-level rise during 1993–2014

      cGlobal mean sea level (GMSL) has been rising at a faster rate during the satellite altimetry period (1993–2014) than previous decades, and is expected to accelerate further over the coming century1. However, the accelerations observed over century and longer periods2 have not been clearly detected in altimeter data spanning the past two decades3,4,5. Here we show that the rise, from the sum of all observed contributions to GMSL, increases from 2.2 ± 0.3 mm yr−1 in 1993 to 3.3 ± 0.3 mm yr−1 in 2014. This is in approximate agreement with observed increase in GMSL rise, 2.4 ± 0.2 mm yr−1 (1993) to 2.9 ± 0.3 mm yr−1 (2014), from satellite observations that have been adjusted for small systematic drift, particularly affecting the first decade of satellite observations6. The mass contributions to GMSL increase from about 50% in 1993 to 70% in 2014 with the largest, and statistically significant, increase coming from the contribution from the Greenland ice sheet, which is less than 5% of the GMSL rate during 1993 but more than 25% during 2014. The suggested acceleration and improved closure of the sea-level budget highlights the importance and urgency of mitigating climate change and formulating coastal adaption plans to mitigate the impacts of ongoing sea-level rise.ry [accessed Oct 23 2018].,

      hmmm a paper in nature vrs some math challenged bullshiter on the web.
      You lose mate.

      oh dear.
      You will not get a rate of change from a linear trend line spanning the entire record.
      Thinking you can shows a less than twelve year old level of math understanding.
      This has been pointed out to you many times already yet it fails to seep into your skull .
      Do you have some sort of leaning disability?

      As to rainfall .
      Physics warmer temperatures means the atmosphere can hold more water .

      This is not disputable ‘but you just did .

      Jesus mate go do some fuckin basic schooling you are embarrassing.

  8. chrism56

     /  October 23, 2018

    As usual Griff, you do the usual irrelevant rubbish. We are discussing New Zealand. The tide data has shown no acceleration. The rainfall has shown no increase in amount or intensity. That is what the post was about. Discuss the actual data, not what you can google in modelling papers which we know you don’t read and can’t understand..
    And as usual and others have pointed out, you get abusive when your arguments are rubbish. That is why you get banned.

    • Griff.

       /  October 23, 2018

      you gotta laugh .
      If you link to a linear trend it says nothing about if the rate is accelerating .
      It is by definition the average rate of rise over the entire record.

      You accuse me of not understanding but its you who cant even get basic math concepts .

      You are arguing with Parliamentary Commissioner for the Environment Jan Wright, World sea level experts John Church and Niel White among many others not “Griff” some dude on the internet.
      Hence this post .
      No one pays loons like you any notice out in the real world.
      Keep making an arse of your self .
      Its funny in a look a loon sort of way and you nuts in denial dont count anyway .

      • Pink David

         /  October 23, 2018

        “No one pays loons like you any notice out in the real world.”

        I would suggest to you, given all the evidence, that the real world is paying far more attention to Chris than yourself. The world continues to use resources it always has, and any changes for the sake of climate change are marginal at the very most.

        • Griff.

           /  October 23, 2018

          Yeah whatever pinky
          Don’t come moaning on here about carbon tax, oil and gas drilling bans, the shift from dairy to forestry. coal mining bans or the fact you will soon be pinged for driving a gas car then boy.
          Or the cost of withdrawing from coastal land you will soon see.
          Carbon free 2050 if right wing coal fired Luddites like it or not .

  9. chrism56

     /  October 24, 2018

    If Griff tries to describe maths, you have to laugh. “If you link to a linear trend it says nothing about if the rate is accelerating . It is by definition the average rate of rise over the entire record.” You only went to school cert maths to eat your lunch, didn’t you.
    Then the trend is about linear- i.e. there is no acceleration. That is why they show the confidence limits And the NOAA data also shows the velocity of change, which shows the 70s were higher than now. So there has been no acceleration in the tidal sea level rises around New Zealand, There has been no intensification or increase in rain. This is all from the actual data. Things might change in the future – we don’t know – but we also might be destroyed by an asteroid strike. However, all the alarmist predictions so far have been wrong, so their track record is worse than astrologers.

  1. 0.5-2.0 metre sea level rise possible, more frequent floods — Your NZ – NZ Conservative Coalition