House by the sea (not a good idea)

The Royal Society of New Zealand has just published an interesting paper on sea level rise [pdf], the latest in a series on “emerging issues” of public concern. It’s a very good overview of the current state of our understanding of the risk of future sea level rises, reviewing the evidence that’s accumulated since the IPCC’s Fourth Report (AR4), and puts that information into the NZ context.

The paper suggests that as we’re learning more about the behaviour of the great ice sheets of Greenland and West Antarctica it’s becoming clear that there’s a risk of sea level rise this century much greater than the upper limits given in AR4 (which ignored increasing ice sheet melt). On the other hand, the extreme rates of sea level rise seen during the last deglaciation (4-5 metres per century at times) look less likely, with data from the last interglacial (LIG, aka the Eemian) suggesting 1.5 metres/century is more plausible.

The RS paper also includes a useful summary of various SLR planning guidelines issued around the world. New Zealand’s guidelines (Bryan’s take here), based on AR4, look to be on the low side, but speaking at the press conference to launch the paper, Prof Martin Manning, director of Climate Change Research Institute at Victoria University , suggested that in his recent experience Environment Court judges were taking care to stay abreast of current scientific knowledge. That’s important, because as NIWA’s Doug Ramsay pointed out at the conference, 12 of the 15 largest towns and cities in NZ are on low-lying coastal and estuarine margins, there’s been enormous pressure to develop on prime beachfront locations and large chunks of our road and rail infrastructure are within 5 metres of current sea level.

[Iron & Wine]

32 thoughts on “House by the sea (not a good idea)”

  1. Auckland’s Fanshaw street upon which sits some very prime commercial real estate. Vodaphone Microsoft Air New Zealand New hotels and plush apartments amongst others, is 1.5 m above sea level. I surveyed the new bus lane into town. Dig down 1.5 m and at high tide your hole fills. It’s reclaimed land anyway. So that area is a gonna. AND we are currently pushing thru a Tunnel to Britomart! Great planning. That’ll be all down the gurgler!

  2. IF sea levels rise, they will not be the only thing effecting the shorelines of our cities.

    Wellington for example had a different shoreline 150 years ago, due to geological changes.

    Just as Wellington is lifting I presume other cities (Tauranga, Christchurch?) are falling.

    Does anyone know what the rate of movement is for our big cities from tectonic forces and how this compares to sea level rise forecast by the IPCC?

    1. From the paper:
      “While, within the limits of present measurement capability, the majority of the New Zealand landmass appears to be relatively stable (despite an expected rise due to a slow adjustment following the last Ice Age), earthquake activity can quickly alter this situation. While the long-term ongoing tectonic effect is small when compared with changes in ocean height, the data we have do not allow us to rule out local changes of height which may increase local risks in areas where strong subsidence is taking place.”

      Ongoing GPS height measurement is underway to pin down exactly how much height change is occuring for many points around the coast. This research hasn’t been published yet, so I can’t say much about it, but these long-term changes are small in comparison to expected ocean height changes. However, you’re quite correct in pointing out that earthquakes can lead to sudden changes in height, altering coastal risks.

          1. R2D2,
            I noticed that too. I got told to “piss off”, “ignorant troll”, accused of mental masturbation, etc etc, and these gets thumbs up!

            Yet when I produce evidence to back up my claims, there is a complete silence.

    2. There’s no “if” involved, only a “how much”. The climate commitment — the amount of warming that will result from current GHG levels as the planet gets back to thermal equilibrium — is enough to guarantee a significant amount of sea level rise over coming centuries as ice sheets adjust to the warmer climate and as the oceans warm and therefore expand.

      1. Sorry. I don’t talk in definite terms as you do. I am humble enough to know that the future is uncertain.

        Putting that aside if you can I believe the rest of the question was a relevant one.

  3. And we should stop talking about the ice-sheets melting. There’s no need for them to melt to cause sea level rise. It only needs warming seas and a bit of melt to increase slippage and calving.

    Once a huge chunk from an ice sheet is in the ocean it might take years to melt (if only). It’s the shift from land to ocean that’s the issue, and why it could cause sudden sea level change.

    The melting Arctic is spectacular but it won’t affect sea levels. Extra gigatons dropping off WAIS or GIS do make a difference. Lots of extra gigatons and we would be in a world of hurt.

    1. Yes Steve I know that. But some people who visit here also visit other sites with very silly posts on ice, melt, SLR. You know the ice “can’t” melt because the air temperature isn’t warm and all that guff.

      The one that scares me is the geography of the GIS. If what I recall is true about the underlying structure being a huge depression surrounded by mountains. It only takes a bit more access for water through a gap to get beneath the great bulk of the ice and start under melt and shifting the gigantic thing a bit. Any hint of gradual SLR from melt will go out the window. That thing is massive.

      1. My understanding is that for Greenland, the surrounding mountains make a good barrier between the warmer oceans and the low interior. At the other end of the world, a large amount of the bedrock under the Western Antarctic Ice Sheet is under sea level and one estimate of sea level rise from it’s collapse is 3.3 metres ( However, in the online briefing about this paper, Dan Zwartz put the time for this to melt at 500-1700 years. The melt could well be unstoppable, but that’s still fairly gradual.

        1. NASA’s Bindschadler (one of the NZ report’s co-authors) thinks the PIG/Thwaites complex may well collapse by the end of this century, resulting in a 1.5 meter sea level rise.

    1. “Collapse” is the word used in that paper. They’re talking about positive feedback situations where some melting leads to more melting. But yes, when glaciologists say collapse, they often mean over thousands of years, which is not what the man in the street would think.

      1. Jez, I came across papers, a few years back, describing collapse of the West Antarctic Ice Sheet, fortunately they detailed what the term meant in the introduction – so a few less worry lines on my forehead. I just wish they had used a less drastic sounding term, there’s enough confusion from the inactivists.

  4. dappledwater,

    hope you don’t mind this off-topic ? but I’d respect your opinion on something we were both reading about a couple days ago.. re the SA H/stick just out.. how could one take ice-core NH3 to proxy temp? Is it related to greater atmospheric concentrations thence annual precipitations etc..? And in using it is sampling summer time only..?

    be grateful as I have to get my head around such aspects..

  5. Tom,

    I don’t know how long this link is going to remain viable, so you might want to have a squizz now.

    The study authors state that the ammonia found in the ice cores are from a biological source (vegetation and soil bacteria emissions) and originate from the Amazon rain forest – prevailing winds carry particulates & aerosols to the glaciers in the Andes.

    Like all chemical reactions this rate of emission is temperature dependent, higher temperatures yield higher rates of emissions – lower temperatures lower emission rates & the ice core deposits of ammonia can therefore be used as a paleo- proxy for temperature in the Amazon.

    That’s the basic gist anyway.

    1. Dappledwater,

      thanks for that.. prevailing winds were/are the obvious issue for me and Amazon-to-Andes makes for most relevant sense.. certainly in terms of a SA record..

  6. This made it onto TVOne CloseUp tonight.

    Deutche Bank are very interested from an insurance perspective, said the bearded Prof. when asked by Mark Sainsbury.

    Funny that, the same company that produced that document that “debunked” sceptic claims.

    No conflict of interests there, then. Nothing to see here, move along.

    1. If you were a bank underwriting insurance companies what would you do? Tell people to build in places by the sea or argue for safer places so that your future exposure to foreseeable risks is minimized?
      Insurance is a community thing. It works great if all try to avoid risks and few pay outs are needed. That keeps premiums down and everybody happy. Building in the firing lines of coming climate change will greatly increase risk. It should be in all our interest that DB is taking a keen interest to minimize the consequences for them and us all.

        1. Yes!

          I think in all the gloom and doom about the deniers camp with their dinosaur grandmasters in the fossil fuel lobby and the strategy rooms of the tea party reactionaries holding the world back at the moment there is one shining ray of hope: The instinct of investors and the calculated greed of shareholders!
          In the end, money has always ended up backing reality as it is, not as it is told, as only fools and their dosh are easily parted while the clever come out on top.

          In the heads of many deep pockets I sense at the moment an epic battle going on: “Shall I stick with my mates and deny climate change because that is politically what I am supposed to do, or shall go with my investor instinct, take a second look at the evidence and throw my money where the evidence says it should be going….”

          I think sanity will win very quickly once money starts moving into the right direction. Then the Moncktons of this world will retreat to the spiderwebs in the attic of their castles again as if they never had been….. because in the end its the money, stupid! 😉

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