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Global sea levels rose faster in the 20th century than at any time in the past 3,000 years – And, Surprise, It’s Your Fault

February 23, 2016

By Paul Homewood 




The Mail is referring to the new paper, Temperature-driven global sea-level variability in the Common Era, by Robert Kopp et al.



We assess the relationship between temperature and global sea-level (GSL) variability over the Common Era through a statistical metaanalysis of proxy relative sea-level reconstructions and tide-gauge data. GSL rose at 0.1 ± 0.1 mm/y (2σ) over 0–700 CE. A GSL fall of 0.2 ± 0.2 mm/y over 1000–1400 CE is associated with ∼0.2 °C global mean cooling. A significant GSL acceleration began in the 19th century and yielded a 20th century rise that is extremely likely (probability P≥0.95) faster than during any of the previous 27 centuries. A semiempirical model calibrated against the GSL reconstruction indicates that, in the absence of anthropogenic climate change, it is extremely likely (P=0.95) that 20th century GSL would have risen by less than 51% of the observed 13.8±1.5 cm. The new semiempirical model largely reconciles previous differences between semiempirical 21st century GSL projections and the process model-based projections summarized in the Intergovernmental Panel on Climate Change’s Fifth Assessment Report.


A bit of mumbo jumbo maybe, but this is how they describe the significance:





This is the latest in the line of “everything is hotter/ wetter/drier/stormier etc etc than ever before”.

When these sort of studies are properly examined by the likes of Steve McIntyre, they quickly lose all credibility. Unfortunately we need an army of Steves to keep up. Hopefully however, he will have time to look at this one.


I do have some observations though, in no particular order:


1) As we know, Greenland ice cores, and other supporting data, show that not only was the MWP warmer than currently, but the rise in temperatures at that time was significantly greater and more rapid than in the last century and a half.

The same applies to earlier warming episodes.

There is no logical reason why sea levels should not have risen at least as fast then.





2) HH Lamb’s Climate, History & The Modern World also shows very rapid changes of upper tree lines in the European Alps around 1000 years ago, both up and back down again, indicating rapid warming there as well.




3) HH Lamb also provides strong evidence that sea levels were at least as high, and probably higher, back in the Middle Ages, and also around 400 AD. In between, sea levels fell, so we know that sea levels have never been the sort of constant thing often portrayed.

For instance, he talks of sea levels dropping by 2 meters between 2000 and 500 BC, a rate of 1.33mm/year. As I think it is safe to assume that this was not a steady rate throughout, it seems reasonable to assume that for much of this period the fall was much greater.


4) The Abstract says this about the period 1000 to 1400 AD:  


A GSL fall of 0.2 ± 0.2 mm/y over 1000–1400 CE is associated with ∼0.2 °C global mean cooling.

In other words, 80mm or 3 inches over 400 years.

But why choose that period? We know that the MWP was still going strong certainly well into the 13thC. But, significantly, Lamb also states:


Sea level was again rather lower in the 7th and 8th centuries, but seems to have been again high in the late 13th to 15th centuries.


In other words, there tends to be lag when glaciers keep melting and sea levels keep rising, even though the peak warmth has gone.

Quite simply, why have not the authors shown the sea level fall during the time when it was certainly at its greatest, between the late 16thC and the mid 19thC? I suspect if they did that, we would simply see that it more than offset all of the rise since.


5) And this brings us to the crux. It is undisputed that there was a massive and rapid expansion of glaciers worldwide during the Little Ice Age. (See my list here, for example)

In the European Alps, this began around 1550, and continued in fits and starts till about 1850. Similarly, glaciers in Greenland and Iceland did not reach maximum till the late 19thC.

Exactly the same patterns are seen in South America, Alaska and New Zealand.

There can be no doubt that sea levels fell during this era by far more than the 80mm quoted for the earlier period.

The only question is whether the sea rise in the last century and a half has simply cancelled that out. The evidence suggests otherwise, but even if it has, so what, We are simply back where we were before. The rapid recovery from the Little Ice Age is no more than a reflection of the rapid descent in the first place.

  1. Randy Hall permalink
    February 23, 2016 9:28 pm

    We know the ocean level was much higher in the past as this place is over hundred miles inland and at least a 1000 foot elevation.

  2. February 23, 2016 10:39 pm

    The notion that sea level rises are man-made is pure assertion. They have no way of finding a difference between natural and ‘unnatural’ (if it exists) sea level rise, so they just label it all ‘unnatural’ – and call it science. Sad really.

  3. TonyM permalink
    February 24, 2016 1:31 am

    The questions still remain:

    “By what methodology have recent sea level measurements been made and used in this report?”

    “Where are the data sets that resulted in the graphs presented?”

    It seems rather preposterous that reports can quote measurements of one-tenth of a millimeter plus or minus 1 tenth of a millimeter on ocean surfaces that are subject to all kinds of minute by minute local and larger fluctuations from tides, waves, storms, winds, earthquakes, tectonic plate movements, melting ice, freezing ice, precipitation, evaporation, and who knows what else. There are some powerful and probably unknown statistical analyses here!

    Is a “semiempirical model” another description for a hockey stick chart? Or does it mean we used some real data and made up the rest?

  4. February 24, 2016 2:55 am

    It is also been demonstrated that NOAA has trebled the sea rise historical data from at least 1980 onward that it initially published on this subject. The fraud continues without precedent in America. Our entire scientific establishment has now been compromised.

  5. February 24, 2016 7:04 am

    According to Epica Dome C ice core data (Antarctica), CO2 levels declined very slightly from 268 ppm 10,458 years ago to 264 ppm 9,399 years ago, but during this period, sea levels rose at rates of 1.4 to 4.8 meters per century (between 10,473 and 9,411 years ago). Sea level high stand was also 8+ meters higher during that time. What caused that rapid sea level rise rate, since CO2 levels declined?
    The field data show rapid increases in rates of relative sea level rise of 12–48 mm/yr between 10,473 (or 9678) and 9411 cal yr BP in the Vestfold Hills and of 8.8 mm/yr between 8882 and 8563 cal yr BP in the Larsemann Hills. The relative sea-level high stands of ≥ 8.8 m from 9411 to after 7564 cal yr BP (Vestfold Hills) and ≥ 8 m at 8563 and 7066 cal yr BP (Larsemann Hills) are over-predicted by some of the glacial isostatic adjustment models considered here, suggesting that assumptions relating to the magnitude and timing of regional ice loss since the Last Glacial Maximum may need revising. In the Vestfold Hills and Rauer Islands the final deglacial sea-level rise was almost exactly cancelled out by local rebound between 9411 and 5967 cal yr BP and this was followed by a near exponential decay in relative sea-level.

  6. Ben Vorlich permalink
    February 24, 2016 8:23 am

    I remember watching something a long time ago, so it must have been BBC or ITV, about the Anglo-Saxon invasions/migrations to England. One of the reasons put forward was rising sea-levels causing problems for coastal communities combined with pressure coming from migrating Franks, Vandals, Goths and Huns. Being coastal dwellers with nowhere else to go and thinking that the sea was going to continue to rise (there’s nothing new in climate science) moving to the UK must have been a simple choice.

    • February 24, 2016 1:43 pm

      There are quite a few such programs. Try google. I watch on my laptop since ridding my home of TV. There are a number dealing with Europe under the last ice age and people living at the edges–literally and figuratively.

  7. Tim Hammond permalink
    February 24, 2016 8:24 am

    Once again a paper that removes the assumed AGW effect from observations and then finds that when you add it back the result looks very like the observations.

    The absurdity is not the modelling – it might be if interest to see what has happened if the assumed cause is correct – but the claim that the modelling somehow proves the assumed cause.

    For some reason lots of these scientists seem confused as to the difference between the former and the latter.

  8. Mark Hodgson permalink
    February 24, 2016 9:15 am

    For the sake of argument, let’s assume they’re correct (controversial, I know). I made a similar point on a discussion thread on Bishop Hill the other day. If our planet has been around for c 4.5 billion years, that’s for us humans an unimaginable timescale. To put it in terms that we can understand, let’s say our planet has been around for one day. On that timescale, 3,000 years represents 1/17 (0.056) of a second.

    Thus, even if we accept that they’re correct – so what? The timescale in question is utterly insignificant in the life of our planet. We need to stop thinking that humankind is everything and that human timescales are in any way relevant to planetary considerations. We need to start thinking on a planetary timescale, then there’d be nothing to be alarmed about – even on the entirely hypothetical assumption that the alarmists have their science correct.

  9. Paul2 permalink
    February 24, 2016 1:24 pm

    Result. Some good news for a change.

  10. February 24, 2016 1:50 pm

    A little factoid. During the heights of glaciation, the Outer Banks have been 50-75 miles further east than they are today. HOWEVER, the old fall lines when sea levels were much higher are just east of Raleigh, NC and Richmond, VA. Take a look on the map…..Raleigh is not quite halfway across present North Carolina. So the height of interglacial melting had the waves lapping at Richmond and Raleigh. Tell that one to the model makers and alarmists (one in the same).

  11. spock2009 permalink
    February 26, 2016 12:04 am

    Perhaps good information but is seriously flawed by references which simply lead back to this site. The only useful references are those to the original paper(s) and this seems to be lacking in this article.

    • February 26, 2016 10:07 am

      All the original articles on my site, which are referenced here, are themselves fully referenced to original papers,

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