Are the seas rising? My perspective on ‘climate change’ #6

Of all the consequences that a warmer planet might bring, the one that gets the largest media shock/horror buzz is the prospect of rising sea-levels, as (some) ‘scientists’  predict that bigger seas will flood coastal communities, submerge coral islands and drown countries like Bangladesh. Greenland will melt, Antarctica will melt, glaciers will retreat even further. We are doomed, unless … It’s just too good a story to spoil with inconvenient data. In fact, as I said eight years ago, there’s just no evidence of anything like this happening. Not one of the fifty million climate refugees predicted for 2010 by the UN Environment Program in 2005 has been found. Another man who personally claimed in 2013 to be a climate refugee has had his claim dismissed by the courts in New Zealand.

The story of the climate refugees is an interesting one. If you go searching for it you won’t find it easily. But it did exist, because I was reading about it at the time. And there was even a map, to show you where the climate refugees would be coming from.



This map shows in  blue the coral islands that will disappear, the pink shows areas subject to hurricanes, the blue circles are large deltas where flooding would occur, and the yellow patches identify areas subject to drought. It was said to be going to happen. It’s a worrying map, and it was intended to worry people. I use it and mention its origin because it is probably the best example of the unfounded ‘scare’ about global warming. It was a complete fantasy. How could anyone with sense have put it out? The UNEP finally pulled it off their website in 2011, and the 50 million refugees claim as well. Unfortunately for the UNEP you can find it elsewhere. It won’t go away.

Are the seas rising? Yes, they are. They have been doing so for several hundred years. Sea levels may have been rather higher in the human past. There are two connected methodological debates about sea levels. The first is whether one should use satellite data or tide-gauge data to measure whatever rise is occurring. The second is whether global sea-levels have any meaning, given that each point on a coastline is affected by different conditions. Land can sink, land can rise, and in each case apparent sea levels will be different. There are many variables involved in measurement, and you can read about them here.

At the highpoint of the scare governments were inclined to use the IPCC predictions of about half a metre increase (double that if you took a worst-case scenario) by the end of the century as a benchmark, and looked at all the awful possibilities should that figure be reached. The IPCC projections are based on satellite measurements, which show a recent apparent acceleration in sea-level rise, while tide gauges don’t. In fact the Fort Denison tide gauge in Sydney harbour, one of the longest-serving in the world) shows very little increase in sea levels at all — about 0.65 ± 0.10 mm/yr for the past 128 years. It is the trend that is important: about 6 centimetres per century, and not anything to worry about.


With the scare subsiding, two governments at least, those of NSW and Queensland, have told local councils that they should use the best available local knowledge, especially local tide gauges, as their point of reference for future sea-level rises, not the IPCC’s projections. As a ratepayer, I advised the Eurobodalla Shire Council along the same lines. Councils can feel vulnerable to court cases based on what might happen and what has happened, and they need some protection. If they go too far along the IPCC path they will cause dramatic falls in property values, and great public fuss. Councils usually have a Green councillor or two for whom greenhouse gas emissions and sea-level rises are much more important than anything else. It’s a difficult situation for any coastal council.

Of course, there is much more to the whole sea-level issue than measurement, though it is central. The basic argument behind the scare is that the world is getting warmer and that a warmer sea will expand in volume. In addition, a warmer world will lead to more glacier-melting, and more ice-loss from Greenland and Antarctica. So the oceans must rise. The IPCC says that It is virtually certain that global mean sea level rise will continue for many centuries beyond 2100, with the amount of rise dependent on future emissions. I would agree with the tendency of the first part of that sentence, since all the evidence suggests that the seas have been rising slowly for a long time.

I would not agree that greenhouse gas emissions have a lot to do with it, for the data don’t really support the IPCC position. Coral islands are growing in size, not sinking. Bangladesh is adding land every year as the Irrawaddy creates more islands. The Antarctic remains stubbornly and solidly frozen, and recent winter sea-ice extents there have been enormous (last winter’s was around 20 million square kilometres, about two and a half times the area of Australia). Greenland gets a lot of snow — much more than the Antarctic — and while it is losing some ice at the side it is gaining it on top. I wrote about the astonishing depth at which some Second World War aeroplanes were discovered years after they had landed on the ice (83 metres in 44 years). There are few instrumented glaciers; some are retreating while others are advancing. In any case, the amount of sea-level increase that could be attributed to glaciers is very small. Nonetheless, those who feel that the IPCC is right have done their best to try to show that the increases are going to come. It is an article of faith for them. I am unpersuaded by the results.

If the world were indeed warming at at the rate at which the IPCC said it would, then there might be something it it. But even with the current el Nino there has been, in the new century, nothing like the warming of  the 1975-1998 period, while of course el Ninos are not caused by greenhouse gas emissions. The whole picture of a world heading to a watery grave rests on the assumptions that CO2 is the control knob of global temperature. If CO2 goes up, temperature must. But as we have seen in earlier posts in this section, it is not at all clear that CO2 is the control knob. Not only that, the relationship between CO2 and temperature is not linear but logarithmic, which means that most of the increase in temperature due to this cause has already occurred.

Further reading: I have written a dozen posts on sea levels and you can get to them by using the magnifying glass icon at the top right of the website page and typing in ‘sea levels’. I greatly appreciate the work of Dr Tony Brown on historic sea-level measurements, and you can read his work there and on related matters by going to the Climate etc website and searching for him. Warning: if you look for ‘rising sea levels’ on the Internet you’ll get about 14 million hits.

Next: How useful are climate models?

Footnote:  A useful collection of essays on this subject can be found on Judith Curry’s website, here.


Join the discussion 87 Comments

  • Alan Gould says:

    Another clear, sane and informative piece Don. Many thanks.

  • Rod Staurt says:

    You can’t get a clearer explanation than that. I admire your ability to articulate the truth without emotion. That is an enviable trait. Thank-you Don.

  • Mark McGuire says:

    Aboriginal Memories of Inundation of the Australian Coast Dating from More than 7000 Years Ago

    Stories are presented from 21 locations from every part of this coastline. In most instances it is plausible to assume that these stories refer to events that occurred more than about 7000 years ago, the approximate time at which the sea level reached its present level around Australia.

    Also, “Twelve Apostles: Limestone stacks found underwater could boost landmark’s numbers”
    The sea stacks, thought to be up to 60,000 years old, were discovered during sonar mapping of Victoria’s southern coast.

    University of Melbourne PhD candidate Rhiannon Bezore, who made the initial discovery in the sonar data, said sea level changes had played a critical role in the structure’s survival.

    “The main factor is that through the past geological changes they’ve been through, the sea level rise has occurred at such a fast pace,” she said.

    “Because of that, they’ve actually been submerged before erosional processes could come and knock them over.”

    If only they had the CSIRO: Carbon tax hit small

  • margaret says:

    About five years ago I read WG Sebald’s The Rings of Saturn, a strange and compelling account of a walking tour of Suffolk in a first person narrative that describes places, people, episodes of history and literature. The changing coastline was particularly fascinating. This paragraph for instance:
    “The Dunwich of the present day is what remains of a town that was one of the most important port in Europe in the Middle Ages. There were more than fifty churches, monasteries and convents, and hospitals here; there were shipyards and fortifications and a fisheries and merchant fleet of eighty vessels; and there were dozens of windmills. All of it has gone under, quite literally, and is now below the sea, beneath alluvial sand and gravel, over an area of two or three square miles… ”

    • margaret says:

      Of course if one lives near the coast in Australia where so many of us cluster there’s awareness of the slow inevitability of encroaching sea levels so maybe one thinks twice about that beach access and view – or maybe not …

  • Aert Driessen says:

    Don, some confusion with the wording here: ” Sea levels may have been rather higher in the human past”. I think that you mean ‘lower’ instead of ‘higher’. As the graph on the link shows, sea levels (SL) have risen some 130 metres in the last 15,000 years (receding Ice Age etc) from a lower position in the human past (the Aboriginals walked across Bass Strait to Tasmania). I just cannot believe that people who are supposed to be ‘educated’ are sprooking this sort of stuff. Not that it’s relevant here, but coral islands are actually formed by rising sea levels, not destroyed. As SL rises, coral grows to keep up with the sunlight. It makes such islands bigger and stronger as reefs grow. That’s how the Great Barrier Reef was formed. Oh well ……

    • Don Aitkin says:

      No, Aert, I meant higher. There are coastline segments that seem to show a higher sea level in many countries. Read the link. I used the verb ‘amy’ advisably, because it is suggestive not decisive. Tony Brown has a most interesting story there. Margaret above also has some evidence. There’s a lot of such quasi-historical possibilities in England. Troy is now a long way from the Mediterranean, if indeed that site is truly that of Troy, and so on.

      • Mike says:

        At the link there is a graph showing it was lower and a statement “So maybe it was higher than today, or maybe it wasn’t”.

        • Don Aitkin says:

          I do hate auto correct. Not ‘amy’ — ‘may’.

          • Don Amoore says:

            And subsiding not subsidising

          • Don Aitkin says:

            Thank you, Don Amoore. I’ve made that change. I am sure that I would be much better off If there were no AutoCorrect, but apparently I can’t get rid of it (according to my local Mac expert). I’ve also made a change at the end, changing ‘computer models’ to ‘climate models’, a suggestion made by a correspondent.

        • Don Aitkin says:

          Mike, that is Tony Brown being careful. But if you read his text he provides examples and counter-examples. Hence my use of ‘may’. Here as elsewhere it is hard to be really sure about what happened in the past.

      • colin davidson says:

        Indeed they do.
        Look up “Fairbridge Curve”.

        That curve shows that we may be experiencing a second-order damped response to a major step change which occurred thousands of years ago, our lifetimes being part of the settling into a new steady state.

        To Don’s examples I would add the Cinque Ports in England, Rye and the Isle of Sheppey (Rye is now inland, was a Roman port, Isle of Sheppey was an Island in Roman times, but now joined to the land.)
        I also note that the Dutch, who live on a major river delta system, about 2/3 the length of coast of the Bangladesh delta, managed to solve their flooding problems in previous centuries (including the 20th) with the use of human labour and horse and cart technologies.
        It seems to me that if the Bangladeshis were alarmed about their future survival, then they have sufficient labour to avoid inundation. Furthermore, using fossil-fuelled machines, flood levees and barrages are very much easier and cheaper to construct than they ever have been in the past, and that cost decreases markedly every year as the machines become more capable, fuel prices decrease, and the machines become more efficient, and as we become more skilled.

        But I think that Don is absolutely correct. The current rate of sea level increase is not alarming, and it is not increasing. Remember the Australian research published I think in 2012 where it was found that in Australasia the sea level rise rate is falling – it seems we are nearing the top of this Fairbridge curve damped oscillation.

    • Mike says:

      If a thriving reef is desired the water is needed is an increased global temperature and rising seas. Then it then GBR will increase its depth as well as extending South.

    • Neville says:

      Aert, there are many studies that show SLs were about 1.5 to 2 metres higher only 4,000 years ago. That was after the end of the warmer Holocene climate optimum. Scientists can show that OZ’s east coast SL was at least 1.5 metres higher then. See ABC Catalyst Narabeen man for eg.

      • Aert Driessen says:

        I’m only just catching up with this feedback and you are right. I had in mind only the ‘big picture’ not individual local scenarios. As I understand it ‘local’ changes in (relative) SL reflect more isostatic adjustments of the crust rather than ‘global’ changes caused by additional volume of water or reduced volume of ocean basins.

  • Paul Goard says:

    For further reading, any papers on the subject by Nils-Axel Mörner are highly recommended.

    As to the published graphs of Fort Denison data, as above, it is rather strange that they end at 2010 or earlier, when the data is available to the beginning of 2016. Even stranger is that since the satellite data has been showing a sea level rise of about 3 mm/year, people such as CSIRO’s Dr John Church has dismissed the tide gauge data, always quoting the higher figure, with no explanation or justification for the discrepancy, considering the satellite precision is so poor.

    Also being a resident of the NSW Eurobodalla Shire, may I assure Don that he was was not the only one to try to convince the Council to make a sensible decision on future sea level rise. Along with several others, some non-residents including the late Bob Carter, we managed a small improvement, against not only the Green councillors, but several members of staff, who selected a consultant whom they were sure would give them the answer they wanted.

  • Anders Valland says:

    I live in Trondheim, Norway. The sea level here was approximately 160 meters higher at the end of the last ice age as compared to today. (link to Geological Survey of Norway, page is in Norwegian). We have land rise comparable to, or higher than, projected sea level rise in most of our coastal areas due to land rise since the great ice age glaciers disappeared.

    • Don Aitkin says:

      Thanks, Anders — that is a huge change!

    • Aert Driessen says:

      Anders, I suggest that this relative rise of SL reflects isostatic ‘rebound’ of the crust after the melting of some 3 km or so of ice that was weighing it down.

  • Don Amoore says:

    Well Don it seems you are comprehensively wrong in all your assertions.
    On Q&A tonight Australia’s Chief Scientist (no less) stated that the 1.5 degree temperature rise recently measured was due to the inordinate and unprecedented rise in CO2 as measured in Hawaii. Another scientist stated that the sea would rise by 80 cm by 2100, and no one dissented.
    Storms are more frequent and more severe they said, and we must consider if we want to save the Opera House.
    The ABC charter demands balance, so who do we complain to, and who do you ask to do a “Fact Check” on all this stuff.
    OMG,SMH or just LOL. We are all doomed.

    • Don Aitkin says:

      I think one just has to accept that the ABC has a fixed view about ‘climate change’ and cannot be relied upon to present news in that domain properly. Now Q&A isn’t news, but I could, if I had the time and energy, mount the same case for News. And in my next essay, coincidentally, I look at the same kind of bias from a well-known ABC presenter.

      • Don Amoore says:

        Yes I know TJ’s leanings are well known but I was shocked to hear the Chief Scientist say what he did. On the news this morning they were reporting that the Chief Scientist said on Q&A that temperature rises were unprecedented and we had lost the fight to control it. No mention of El Nino anywhere.
        The other panelists were equally “Establishment”.

        • Don Aitkin says:

          And the audience is a cheer squad. I had to go and download the session to see what had happened. I find Q&A to be intellectually abhorrent.

          • David says:

            What is so intellectually abhorrent about a discussion about gravitational waves?

          • David says:

            “Intellectually abhorrent? You need to get a grip.

          • Don Aitkin says:

            Why ‘intellectually abhorrent’? It is a question and answer show about big themes, with a handpicked set of questions and questioners, a pronounced bias, and a cheer squad of believers. I’ve seen a few programs and each has been the same. The best one actually had a critic of the orthodoxy, Stewart Franks, who made Suzuki look like the ignoramus he is. TheMC seems to have an extraordinarily high opinion of himself, the reasons for which are not evident on the program.

            No, I think ‘intellectually abhorrent’ is about right. It is a pretence at a discussion, not a real one.

          • gnome says:

            It’s intellectually abhorrent. Even if I cared what a moslem feminist pretends to think about global warming, I couldn’t bring myself to care what a US comedian thinks about homelessness in some part of Australia (s)he couldn’t find on a map. I couldn’t be bothered watching it, even to sneer.

            (I’m assuming that “intellectually abhorrent” has about the same meaning as “a wankfest”.)

      • David says:

        Don What do you expect the ABC to do? Asking the ABC to give denialists equal time because Throbbers mentions AGW on some music show is like anti-vaxers demanding equal time because the ABC does a story on whooping cough. Like it or not both schools of scientific thought are very much outside the current scientific consensus.

    • JimboR says:

      “On Q&A tonight Australia’s Chief Scientist (no less) stated that the 1.5 degree temperature rise recently measured was due to the inordinate and unprecedented rise in CO2 as measured in Hawaii.”

      Here’s what he actually said….

      [Climate emergency?] “Look, it’s probably too early to say that, but that rise is consistent with the trend so even though it’s one month and it’s almost aberrantly high, you wouldn’t want to dismiss it. ….. and it’s also consistent with another figure that came out yesterday, which was the measurement from Hawaii of the level of carbon dioxide in the atmosphere….. and so the temperature rise is not necessarily directly linked at that magnitude with the carbon dioxide increase but they’re all part of the same bundle. ” (

      “The ABC charter demands balance”

      They had quite an eclectic handful of scientists on with very diverse backgrounds (none of them from climatology). The fact that none of them represented your opinions might be more a reflection on your opinions than it is on any ABC bias.

  • margaret says:

    Who are we non-scientists to believe? If we’re of average to above intelligence but have not been taught to think and question it’s impossible to not to take the ‘experts’ like the Chief Scientist as giving us the correct facts – ordinary folk cannot sift through scientific data presented to find the truth about ‘climate change’ and its impending consequences. Unfortunately it seems the ‘experts’ are just ordinary folk also!

    • Don Aitkin says:

      Margaret, I agree that it is awfully difficult, and that is why (I hope) you keep reading here, because you will find here what is not mentioned on the ABC. All media have to be selective, and it is their editors who choose what is to be talked about, what can be left for another time, and what is not to be talked about at all. I’ve been an editor (briefly and when young), and I know that it is difficult.

      Re the Chief Scientist. His is a political appointment, not an arms-length one, so you might consider that what he tells you is what will not upset the government of the day — he can’t say something that is flatly against the current policy. He ought to know something about climate science, even though he is an engineer and neuroscientist.

      Actually, I thought he did a decent job of trying to stay on message with the program and the audience, but not doing the dirty on either the CSIRO or the Government. And I think he has a lot to learn about how to do the job. Here’s hoping…

      • JimboR says:

        “because you will find here what is not mentioned on the ABC”

        Indeed… even when it claims to be quoting what was on the ABC! Both Dons here have form at verballing what the experts actually say and then attacking that. I used to think this verballing was a form of deceit but I’m wondering now whether it’s more a personality trait. I sense that skeptics are very black-and-white kinda’ people. Either A causes B, or A has no relationship to B, with nothing in between. If you can find any place or time where A happened without B, or B happened without A then that proves there is no relationship between them.

        Skeptics appear to struggle living in a world of probability distribution functions. When experts use careful language like “Is consistent with” or “increases the probability of” all skeptics hear is “causes” and then they head off into a rant about that. My advice to Margaret would be to listen carefully to what the experts in the field say and ignore (or at least double check) what correspondents here claim they said.

        • Don Aitkin says:

          One of the great weasel phrases is ‘consistent with’. The average warning of the 20th century is consistent with the ending of little ice age, as well. Not only that, it is consistent with the increase in teachers’ salaries and the decline in piracy. That trends are ‘consistent with’ other trends is really of little consequence, but such relationships are paraded as though they mean something.

      • Aert Driessen says:

        Don, I would have thought that even as a political appointment he could have been more ‘neutral’ with statements along the lines of more ‘uncertainties’ that need investigation etc. This guy has sold his soul. He does not deserve respect.

    • Bryan Roberts says:

      margaret, it is perfectly possible for ordinary people to ask sensible questions that merit answers. The following has been presented on several fora, usually to a torrent of contempt and personal abuse.
      “If glaciers are rapidly melting at current temperatures, exactly how will holding an increase in global temperature below two centigrade degrees prevent or ameliorate the situation?”
      I have never received an answer.

  • David says:

    No, I think ‘intellectually abhorrent’ is about right. It is a pretence at a discussion, .

    So what was so objectionable about the discussion on gravitational waves? I thought it was really interesting. I know nothing about them, But I really enjoyed that guy’s enthusiasm and optimism for what they did.

  • Don Aitkin says:

    There was no discussion. It was essentially a piece of news, with the questioner and the panel agreeing that it was special, unprecedented and extraordinary. Oh, and that Einstein had predicted the waves, and he was proved right. Actually, the search for them started before 1990 and LIGO, because I remember the physicists wanting money for an observatory a few years earlier. The Australian site was to be in Western Australia. It got some support, and the AAS liked it, but it was a lot of money, and the ARGC physicists weren’t convinced.

    Now, about ‘climate change’, just to get back to the thread. That was a great discussion, wasn’t it…

  • chrisl says:

    They absolutely fear debate. Anytime there is a debate they are absolutely skewered.

  • Neville says:

    If you remove NATURAL El nino events from the last 37 years there doesn’t appear to be much of their AGW to be found at all. Remember the Le Clerkq world glacier study showed a slowing of retreat since 1950. So where’s the impact from increased co2 emissions ?

      • Neville says:

        Thanks for that reference to a NATURAL attribution to the Planet’s climate variability. It’s called an El Nino event.

      • Ross Handsaker says:

        This article refers to anomalies in temperature, not actual temperature. The actual temperature for February 2016 was well below that for example, of the months of June, July and August of 2015. The actual temperature of the earth fluctuates nearly 4 deg.C each year with the warmest months being those of the Northern Hemisphere summer.

    • bobo says:

      Why don’t you pick a temperature data set of your choosing and run a least squares linear regression for the past 37 years and see what you get. Then you can tell us the trend that you get instead of making vague statements. Because El Nino episodes are spikes they should not influence the trend of the regression model much (you can check this by replacing each El Nino year with an average of the year before and after, for example, and running another linear regression).

      While you are at it, why is it that presumably you and definitely your ilk used the 1998 El Nino event to “support” your claims that global warming ended in 1998 while downplaying the fact that it was an El Nino year? In a few years you will probably be saying “global warming ended in 2016” and will downplay the 2015 El Nino. It’s strategic argumentation (better known as motivated reasoning) that would make any two-bit politician proud.

  • Neville says:

    Co2 Science has done an enormous amount of work over the years. They have references to hundreds of PR studies covering all the ICONS of the urgers so called CAGW. See down this page for many PR studies of SLR.

  • Neville says:

    Here is the link to ABC Catalyst ” Narrabeen Man”. Read transcript about 8 comments down about SLs at Sydney 4,000 years ago. Interesting video to watch about this spearing death long ago.

  • Neville says:

    Sorry about double entry above. GGRRRR.

  • Neville says:

    The Royal Society has two graphs showing SLR for the next 300 years. These are all the models as used by the IPCC. Antarctica is negative and Greenland shows positive for SLR. So where is their dangerous SLR out to 2300?

  • Neville says:

    Another good site with over 1350 PR studies supporting sceptic’s arguments about their so called CAGW. Just scroll down for SL studies.

  • Neville says:

    The Royal Society and NAS joint report claims that there is nothing we can do to change Co2 levels for thousands of years. BTW that’s even if we stopped all co2 emissions today. The scientists who compiled this study arte certainly on the alarmist side of the ledger.
    Here is their point 20 from the report. Little wonder that Hansen called COP 21 just BS and a fra-d.

  • margaret says:

    Being a clever/dogmatic sceptic with an opinion and data that is contrary to orthodox opinion and data with runaway mainstream popularity doesn’t solve the problem.
    To no-one in particular, just those who are less sceptic than deniers because of their certainty. Sceptics are not certain … ?

    “Mr. McGuire: I want to say one word to you. Just one word.
    Benjamin: Yes, sir.
    Mr. McGuire: Are you listening?
    Benjamin: Yes, I am.
    Mr. McGuire: Plastics.”

  • Neville says:

    Interesting to find that all ice core studies show temp changes first and co2 follows after 100s and sometimes thousands of years. Here’s a good summary from Co2 Science.

    Also the 1999 Petit et al study found that co2 lagged temperature after the end of the Eemian interglacial by about 8,000 years. This means that temp fell to ice age levels but co2 remained high for another 8,000 years. Not much of a driver of climate but certainly a follower.

  • bobo says:

    “I would not agree that greenhouse gas emissions have a lot to do with [sea level rise], for the data don’t really support the IPCC position. Coral islands are growing in size, not sinking. Bangladesh is adding land every year…”

    Don, what do you think is producing the satellite altimetry-measured global average sea level rise of 3mm/year? Do you honestly believe that it is due to some coral islands increasing in size and more sediment being deposited in the delta of Bangladesh (I think you mean Ganges, Irrawaddy delta is in Myanmar)? Additional landmass is not going to effect the sea level in the vast majority of the oceans, the gravitational effects are too weak beyond the local tide-gauges.

    “the relationship between CO2 and temperature is not linear but logarithmic, which means that most of the increase in temperature due to this cause has already occurred.”

    Actually, CO2 concentration is growing exponentially (with a doubling time of ~35 years), so increases in temperature should be roughly linear.
    See f or, even better, try fitting an exponential and a linear regression to the Mauna Loa CO2 data and see which has the best fit.

    “But even with the current el Nino there has been, in the new century, nothing like the warming of the 1975-1998 period”
    The two time series do have different lengths, and the shorter one is more exposed to natural variability, so you’re not really comparing like for like.

    • bobo says:

      Submitted comment prematurely. To follow on from my last point, there is a way to compare trends via a breakpoint analysis to check if the difference is statistically significant, a quick glance isn’t really sufficient, you need to take into account the standard errors and number of data points for each section of the time series.

    • Neville says:

      Bobo satellite SL data is adjusted to find about 1 foot rise in a century. But the actual NOAA GLOBAL coastline tide gauge measurements show about 1.5 to 2 mm a year. That’s about 6 to 8 inches per century , or zero change compared to the previous 100 years. So where’s the impact from human co2 emissions since 1950?
      Of course Sydney shows about 0.65 mm a year and Brisbane 0.09 mm a year. That’s about Syd 2.6 inches and Bris 0.36 inches per century. Stop clutching at straws.

      • bobo says:

        Although I have not read much on the matter, I suspect that sea level rise from the 1800s to today is a result of global warming, even if climate modelling can only discern a warming signal distinct from natural variability in the surface air temperature from the 1970s onward. Oceans mop up most (93%) of the accumulating energy in the climate system and the resulting thermal expansion (along with ice melt) to cause sea level rise is probably the best proxy for global warming. What else could cause sea level rise over a long period?

        Regarding local sea levels in coastal areas, there are a range of phenomena that influence measurements, but these influences disappear away from landmasses. Satellite altimetry is an extremely precise technique for measuring changes in sea levels.

        • Charles says:

          I suspect Bobo that you are right in that global warming is responsible for SLR since the 1800’s as we have been on a 250 odd year of normal temperature increase as we progress out of the LIA. That these cycles take place is not contested and we have a documentary record going back at least 2 millennia to the Greco-Roman warming period as well other physical evidence that confirms this.

          The question we have at the moment is that is the SLR abnormal for this particular period? It seems that the amount of rise over the longer period (~ 100 years or more) is at a rate that one could only assume is completely natural, and the only argument that can be made is that there are shorter cycles (~ 5-10 years) , when there are rises that occur that are significantly greater, but are they a factor of melting ice, or other geophysical factors at play such as tectonic plate movement, etc?

          I think it is safer to look at the big picture when examining climate change and ignore the micro changes that tend to get extrapolated out to explain the wider view and which ends up in some quite ridiculous assertions.

        • Ross Handsaker says:

          “Satellite altimetry is an extremely precise technique for measuring changes in sea levels”. Is this before or after the adjustment of 0.3mm for the calculated vertical land motion?

        • JimboR says:

          According to geophysicist Prof Frank Stacey, we aint seen nothing yet. It’ll be our ancestors that really cop it bad:

          [Disclosure: Prof Stacey was one of my first year physics lecturers at UQ and probably my most inspiring lecturer ever. Almost four decades later his voice sounds exactly as I remember it.]

          • JimboR says:

            descendants… not ancestors… they’re blissfully unaware!

          • dlb says:

            Thanks Jimbo, very thought provoking.

            I thought the physics of the Venus’s atmosphere was rather settled science, a bit like the greenhouse effect here on earth. But here comes Prof Stacey with dragon slayer reasoning that its not CO2 but convection that is the driver of the extraordinary heat measured at the surface of that planet. He certainly upset one knowledgeable commenter who did a good job giving the standard explanation of the high temperatures due to the thickness of an IR opaque atmosphere. I don’t know if Stacey is right or wrong but the take away message I got is the science is not always what it seems. Robyn Williams said as much at the introduction, rather ironic I thought for someone who has almost religious devotion to mainstream climate science or any science for that matter.

            Stacey then retuned to the fold by explaining how all the extra heat from CO2 will build build in the ocean and eventually enter the atmosphere at a higher equilibrium temperature, thus melting ice caps and generally being a problem for future generations. Again he may be right, but I think this is just another example of scientific speculation that takes on a life of its own.
            I found his description of Kepplers Laws and the amount of radiation earth receives each year interesting.

          • JimboR says:

            Yes dlb, I agree it’s somewhat radical. Digging further it looks like that Ocham’s Razor presentation was based on excerpts from a book he’s co-authored with Jane Hodgkinson entitled “The Earth as a Cradle for Life : The Origin, Evolution, and Future of the Environment” which claims to break away from other misunderstandings common even within the scientific community.

    • Ted O'Brien. says:

      “..what do you think is producing the satellite altimetry-measured global average sea level rise of 3mm/year?”

      The satellite altimetry was used by sceptics years ago now to show that alarmist claims were wildly exaggerated. How it got to be the counter argument I do not know. Have the satellite data also been “homogenised”?
      Above we see a chart from the noaa’s tides and currents record for Sydney’s Fort Denison. There are two absolutely significant features of that chart.
      1. It shows a very consistent rise of .65mm a year over a century and more, with absolutely no acceleration during the high emissions period over the last 20 years prior to 2010, and 2. It terminates at 2010.
      Other published records at noaa do not terminate at 2010. Fort Denison has not moved since 2010. So, why do noaa not publish Fort Denison’s record since 2010? The only logical explanation is that noaa are trying to excise data which runs contrary to their policy.
      Back to the actual sea level. It is at the tide gauges, not at the satellites, that sea level rise will bring disaster if it happens. And at Sydney it certainly is not happening in a manner to cause alarm. On the east coast of the US the rise indicates that the land there is sinking, which would not be caused by atmospheric events. A brief look at noaa’s records does not give the impression that the rise over the last century was as high as the 20 cm we have been told. So maybe that should be checked out with Nils-Axel Morner.

  • Neville says:

    But please can the urgers tell us how to mitigate their so called CAGW? Remember your answer will be carefully studied to make sure it isn’t what even Hansen calls BS and a fra-d. ( left out U to stop another hold up in moderation)

  • Neville says:

    Here is the link to the 2014 Le Clercq world glacier study. They found that there was a slowing of retreat after 1950. And the 1920 to 1960 retreat was much greater than the period 1960 to 2000. Food for thought?

  • Ross Handsaker says:

    Bobo says : “What are you talking about?

    RS Nerem et al “Satellite Measurements of Sea Level Change”.

    3. Sea Level Change in the Satellite Era.
    Inter alia “after taking into account glacial isostatic adjustment correction of (-0.3 mm) per year”.

    • bobo says:

      This would not significantly affect the global average sea level results, this is relevant for coastal areas only

  • bobo says:

    There’s an interesting figure for sea level over the past 2500 years at Real Climate:

    In particular, during the medieval warm period (950-1250 AD) the sea level generally fell. This probably indicates that the MWP was not global in extent; a global MWP should have caused thermal expansion of oceans and increased ice melt, hence an increase in sea level.

    Additionally, during the so called Little Ice Age (1300-1800s) we see that sea level declined slightly until about 1400 (slight global cooling? if so, consistent with a global LIA), then increased rapidly between 1450 and 1550 (global warming? this would contradict that this stage of LIA was global), and a general decline from about 1600 to 1850 (global cooling? if so, consistent with global LIA).

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