Sea Levels Were Higher In The Middle Ages
By Paul Homewood
This paper was published in 2009, but it is still highly relevant:
I have highlighted the key conclusion, that global sea levels fell by between 31 cm and 47 cm between the MWP and LIA.
Although the LIA minimum occurred around 1730 AD, most of the sea level rise since really only began in the late 19thC, or even later as indicated in the tidal gauge records for Brest, one of the longest datasets:
We know that since the late 19thC , sea levels have risen by maybe 25 cm. So Grinsted’s conclusions imply that MWP sea levels were higher than present. HH Lamb came to similar conclusions in the 1970s.
It is worth pointing out that Grinsted’s model is based around two temperature reconstructions:
- Moburg et al (2005), which has a pronounced MWP and LIA
- Jones & Mann (2004), which has much less MWP/LIA amplitude
The Grinsted paper concludes:
We further find that the Moberg et al. (2005) temperature reconstruction is more consistent with observed sea level rise than the Jones and Mann (2004) reconstruction which we conclude does not have a cold enough Little Ice Age.
The model results are also calibrated against reconstructed sea levels using tidal gauges, (see above graph), giving what the authors describe as “good predictive power”.
Whether the world is 2 to 4 degrees warmer than today by 2100, as the authors suggest, is highly debatable!
But what is apparent is that current sea levels are not unprecedented in recent history. Indeed they point that present sea level is within ~20 cm of the highest level for 110 000 years. This is not in any way alarming, given that most of those 110,000 years spanned the last ice age, and that since then global sea levels have been steadily rising.
In 100 years time, we may get back to MWP sea levels.
Comments are closed.
NOT A LOT OF PEOPLE KNOW THAT 
I do not believe for a minute that global temperatures, rising slightly since the Holocene Climate Optimum ended 5,000 years ago, were ever higher than they are now. This so called reconstruction is BS.
I meant to type’
Rising global temperatures since 5000 years ago would NOT have caused global sea levels to ever be higher than they are now. Sea level has been rising for at least 5,000 years as the oceans warmed.
Paul, if I may:
As shown in Mark s links , sea levels were a lot higher in the the past .
In Roman times it was hotter than now , and several Roman ports which were in use then are now some way from the sea .
But the media and Eco Loons will still keep bombarding everybody with their desperate attempts to claim Global Warming .
Pevensey Castle comes to mind.
And the Water Gate in the Tower of London was constructed in the 1270’s and is still available? at higher tides.
And Pevensey Castle built by the Romans on a promontory surrounded by sea on 3 sides. There are YouTube from the air showing a road around it now.
Their ABC Catalyst also highlighted this story about the Narrabeen Man death at Nth Sydney about 4,000 years ago. They mention that SLs were about 1.5 metres higher then than today. This seems to tie in with your research of these latest studies.
https://www.abc.net.au/catalyst/narrabeen-man/11010512
Here is the Sydney/Fort Denison edition https://www.youtube.com/watch?v=KCELmJ5VGpY
The paper concludes that according to their model calculations, sea level will rise up to 3 times more than that estimated by the IPCC.
I take it from Paul’s article that we should take notice of this paper as it proves a point, but we must not fall into the trap of cherry-picking. 3 times the IPCC prognosis for 2100 would certainly be worrying.
There is also an argument against the mediaeval warm period not being global, and I am curious what proxies were used. One can argue from both sides.
What about the earlier Minoan warming? It would have been useful for that to be included too. I still have memories of sailing off the southern Turkish coast east of Marmaris, and wondering why the site of the old Minoan harbour was some 2 metres higher than what would have been logical. Plate movement would be one reason, but as far as I could make out, the area has since not sunk or risen.
For me the paper raises more questions than answers, and should be noted, but not be taken as gospel.
The paper seems to be largely gibberish. Everybody is wrong but there’s a well-established model? Previous temperature reconstructions are right but aren’t cool enough. Their model fits with the data but shows three times as much warming in the future?
The little ice age was global but variable its visible in most ice cores. The Greek harbours in Turkey that stand 2M above the current levels are not tectonicaly impacted but the sea level is impacted by salt content so rainfall driven.
But if you go to northern Crete there are harbours several metres below current sea level.
(Travelling so can’t give source but I think it was Peter Green’s book on ancient Greece)
I have believed for 50 years that there is a massive treasure of archeological artifacts at the mouth of the Columbia River, i.e., where it was 10,000 years ago. 10 miles out in the Pacific, and 325 feet down.
I also believe Atlantis will be found on the bottom of the Black Sea.
Sea level rise is not going to cause significant damage to any civilisation worthy of the name, so it seems rather wasteful to damage civilisation in the name of curtailing the problem.
When I first heard of sea level rise as a danger – allegedly – it was claimed “millions will drown.” I thought, “They can’t just move up the bank a few feet . . . in a hundred years?”
Or sit on a chair until they die of Old age! 😉
So lets look at this laughable nonsense with some form of objectivity…
From the Abstract in bold:
We use a physically plausible 4 parameter linear response equation to relate 2000 years of global temperatures and sea level. We use a model with an algorithm and some data which we assume is homogenous, even though it can’t be. Which means it is a guess.
We estimate likelihood distributions of equation parameters using Monte Carlo inversion, which then allows visualization of past and future sea level scenarios.
We estimate (educated guess provided our education is up to it) what the past might have looked like and what the future might look like.
The model has good predictive power when calibrated on the pre-1990 period and validated against the high rates of sea level rise from the satellite altimetry.
The model (GIGO) has good predictive power when calibrated on the pre-1990 period (calibrated on what data precisely? Any homogeneity in this data at all? And validated (seriously, validated?) against the high rates of sea level rise from the satellite altimetry. Oh FFS! The satellite altimetry cannot be compared with any sort of empirical dataset. The satellite data have all sorts of estimations and assumptions built in. You are NOT comparing sea level with any coastal or even proxy SL data. The longest dataset from satellite altimetry (any guess as to why it is called altimetry?) is around 40 years. Sea level measurements at a coast have virtually nothing to do with global temperature increase (thermal expansion of water) because the depth of water is insufficient to show a measurable comparison. Apples and Oranges
Future sea level is projected from IPCC temperature scenarios and past sea level from established multi-proxy reconstructions assuming that the established relationship between temperature and sea level holds from 200-2100 A.D. So, a projection based on a model based on several assumptions or estimates or non-homogenous datasets but validated (again, seriously?) because the political body whose sole purpose is to provide so-called evidence of a Climate Crisis to hoodwink the proles into paying for stuff they never needed in the first place.
Over the last 2000 years minimum sea level (-19 to -26 cm) occurred around 1730 AD, maximum sea level (12 to 21 cm) around 1150 AD. Sea level 2090-2099 is projected to be 0.9 to 1.3 m for the A1B scenario, with low probability of the rise being within Intergovernmental Panel on Climate Change (IPCC) confidence limits. We guess.
And all the courtiers agreed with the Emperor…