Bishop Hill Sea level rise - some issues
Feb 16, 2014 This is a guest post by Nic Lewis.
The recent Met Office report 'The Recent Storms and Floods in the UK' makes the striking claim that a further 11-16 cm of sea level rise along the English channel is likely by 2030, relative to 1990 and including vertical land movements, at least 2/3 of which will be due to the effects of climate change:
"Sea level along the English Channel has already risen by about 12cm during the 20th century; this is over and above the increases associated with sinking of the southern part of the UK due to isostatic adjustment from the last Ice Age. With the warming we are already committed to over the next few decades, a further overall 11-16cm of sea level rise is likely by 2030, relative to 1990, of which at least two-thirds will be due to the effects of climate change. We are very confident that sea level will continue to rise over coming decades as the planet continues to warm, and these numbers represent our current best estimate for the UK."
At the risk of being wrongly accused by Julia Slingo of making a personal attack on her - as she is the first named author of the report - I would like to query these particular claims.
The Met Office report sources the 11-16 cm range to projections from the discredited (IMO) UKCP09 projections based on low, medium and high emission scenarios, here: www.ukcip.org.uk/wordpress/wp-content/PDFs/UKCIP_sea-level.pdf - Table 2. Figure 1.2 in that document implies that land along the English Channel will sink by about 3 cm between 1990 and 2030. Deducting that from the Met Office 11-16 cm forecast for sea level relative to the coastal land leaves 8-13 cm from the absolute rise in sea level. It appears that the claim that at least two-thirds of the rise will be due to the effects of climate change comes from comparing 8 cm with 11 cm; in this context the statement implies that such climate change is anthropogenic.
The Met Office’s figure for a rise of 12 cm in the English Channel during the 20th century comes from a paper by Wahl et al (2013) (here). However, these results – which are for absolute sea level - show almost no acceleration in sea level rise. At 0.13 cm/year, the trend over 1993-2009 was only 0.1 cm/year higher than the trend over 1880–2009. Moreover this figure for the most recent rate of sea level rise may be inflated by a non-anthropogenic factor;. it looks from the Gregory et al (2013) 20th century global mean sea level rise paper that recovery from the cooling following the 1991 Mount Pinatubo eruption accounts for a slightly higher rate of sea level rise during 1993-2009, and indeed the post-1993 rate of increase tailed off after 2000.
If we therefore assume a perhaps more representative melded rate of 0.125 cm/yr for sea level rise in the English Channel and apply it over the 40-year period 1990-2030 we can show that on current trends, sea level will rise by only 5 cm by 2030. Some 2.5 cm ot this had been realised by 2010 (extrapolating from 2009). So to reach even the low emissions Met Office UKCP09 projection of 8 cm by 2030, will take another 5.5 cm of sea level rise and therefore the the rate of increase over 2010-2030 would have to be over double that experienced between 1990 and 2009. To reach their high emissions projection of 13 cm by 2030, the rate of increase over 2010-2030 would have to quadruple from its rate during 1990-2009.
How realistic is this? As we are often told, globally emissions have been following high scenarios – close to RCP8.5 – not low ones. UKCP09 uses the old IPCC SRES scenarios B1, A1B and A1F1, which in terms of the IPCC's new RCP scenarios correspond roughly, up to 2030, to respectively between RCP4.5 and RCP6.0, between RCP6.0 and RCP8.5, and somewhat above RCP8.5. We thus seem to be following an emissions path between those used in the medium and high UKCP09 projections, on which basis those projections imply that absolute sea level will rise at least three times as fast over 2010-2030 as it is estimated to have done from 1990 to 2009. Does that have much credibility? According to the IPCC AR5 report, it does – Figure 13.11 projects an even higher absolute sea level rise of ~16 cm from 1990 to 2030 under RCP8.5 (adjusting from a 1986-2005 to a 1990 baseline). However, the global climate models used for both UKCP09 and the IPCC AR5 report have equilibrium climate sensitivities (ECS) that are the best part of twice as high as implied by the best forcing etc. estimates in AR5, whereas for transient climate response (TCR: climate sensitivity over a 70 year period of increasing CO2 concentration) their excess is only about 50% over sound observationally-based estimates. The shortfall of TCR from ECS reflects heat being absorbed by, primarily, the ocean. That implies the models used for the UKCP09 and the AR5 projections put far more heat into the ocean than empirical estimates indicate they should. This would only account, very roughly, for circa 1 or 2 cm of sea level rise, on respectively low and high emission cases, over 2010-2030. But that only explains part of the gap.
Another factor that should give us pause for thought is how little sea level rise there has actually been in the English Channel. Under RCP8.5, 6 cm or so of the post-1990 sea level rise was projected to have occurred by 2010 – or circa 5 cm adjusting for half an excess rise of 2 cm over 1990-2030 due to excessive ocean heat uptake in models. However, as we have seen, the Wahl paper shows that the rise was only 2.5 cm. I haven't figured out why the discrepancy is so large – I am puzzled. Maybe a Met Office sea level expert has the answer. Perhaps it is something specific to the English Channel - the Wahl paper shows absolute sea level rises there increasingly lagging those in the North Sea. If so, is there any reason for the factors involved in moderating sea level rise in the English Channel to cease to operate before 2030?
Even were the Met Office, against the odds, to be right that absolute sea level rise in the English Channel over 2010-2030 will be twice to four times as fast as over 1990-2009, their claim that the relative rise will be at least two-thirds due to (anthropogenic) climate change is indefensible. By no means all the absolute sea level rise over 1990-2010 is related to (anthropogenic) climate change. Figure 13.4 of the IPCC AR5 WGI report shows that land water storage accounted for about 0.75 cm of sea level rise over that period; Figure 13.10 indicates a slightly faster contribution from now on. Moreover, the AR5 WGI report indicates (section 13.3.2.1) that the decline in global glacier volume began in the 19th century, probably as a result of warming after the Little Ice Age, before significant anthropogenic climate radiative forcing started, and did not increase significantly (from a level of 0.6-0.7 cm/decade) during much of the 20th century. If one deducts, from the Met Office low 1990-2030 forecast absolute sea level rise of 8cm, a continuation of the non-anthropogenic glacier melt contribution at 0.65 cm/decade (2.6 cm) as well as the 1.5 cm for land water storage, only 3.9 cm is left as attributable to anthropogenic climate change. That is only 35% of the forecast relative sea level rise of 11 cm - a far cry from two-thirds.
Reader Comments (51)
I think the most eloquent rebuttal for this claim would be a simple graph showing actual English Channel sea level rises for last 100 years with the MET Office's prediction.
Slingo is fighting for her political life. The real sea level change is likely to be negative as we enter the new LIA. The proof that we are doing so is the current weather, exactly what happened in the 1950s during our last period of cooling.
As a child in 1956, I moved to an army camp perched above the Pembrokeshire cliffs. The camp anemometer had just blown off its bearings at 137 mph as the area was devastated by a major storm. As I write this I see Miliband E claiming climate change from CO2: it ain't from that effect, which is near zero, but the scaremongers are fighting hard to panic the public into accepting totalitarian, Marxist government.
Sunday morning's rant against the unholy marriage of computing and physics:
A rise of 12cm in 100 years does NOT mean a rise of 0.12cm per year. Or a rise of 0.00032854911cm per day. Or a rise of 3.80265185e-9cm per second.
Like with the Planck distance in quantum physics, there IS a limit below which figures become absolutely meaningless (apart from when climate science is involved /sarc).
I might be wrong, but in the case of sea level rising across hundreds of miles of coastline, such limit is in the region of the tens of cm, or tenths of meters. There is no way to meaningfully measure smaller values than that, considering the extreme variability from place to place, and the comparably enormous day-to-day changes in sea level, not only due to tides, but at every storm if not for every noticeable wave.
(Not to mention the extreme unlikelihood of the sea inflating itself in some linear manner)
It's as if I measured the distance from my chin to my keyboard down to the micron (10,000-th of a cm)...of course there are devices that can do that, but with me constantly a-moving, there is no real meaning for any figure below, say, the cm.
End of the Sunday morning rant. Perhaps we should add metrology and numerical analysis (ahr ahr) to statistics as the sine-qua-non of climatology discourses.
(The rant is for the same reasons why I cannot bear people talking of ocean acidification...another sour (!) point of climate-related ignorance plus reification, brought about thanks to sloppy scientists trying to scare and simplify things for clueless journalists and politicians. Exactly as for sea level rising.)
In 1946 we lived in a house where the king tides used to cover the level lawn by about an inch and you had to keep a levy intact around the well to stop it filling with salt water.
68 tears on that same lawn is around 8 inches above Highest Astronomical Tides at normal BP and has been for the last few years.
That lawn is on the opposite side of the world in Moreton Bay but if SLs are not rising in 68 years here, they probably aren't doing much over there either.
Flood fight at the Met Office
paragraph 5, line 4; should that 0.1 be 0.01?
Martin A: Your comment is inappropriate here and should be moved to unthreaded.
Daily Mail
Climate expert: No, global warming did NOT cause the storms, by David Rose
Mat Collins, a Professor in climate systems at Exeter University, said the storms have been driven by the jet stream+10
Mat Collins, a Professor in climate systems at Exeter University, said the storms have been driven by the jet stream
One of the Met Office’s most senior experts yesterday made a dramatic intervention in the climate change debate by insisting there is no link between the storms that have battered Britain and global warming.
Mat Collins, a Professor in climate systems at Exeter University, said the storms have been driven by the jet stream – the high-speed current of air that girdles the globe – which has been ‘stuck’ further south than usual.
Professor Collins told The Mail on Sunday: ‘There is no evidence that global warming can cause the jet stream to get stuck in the way it has this winter. If this is due to climate change, it is outside our knowledge.’
His statement carries particular significance because he is an internationally acknowledged expert on climate computer models and forecasts, and his university post is jointly funded by the Met Office.
Prof Collins is also a senior adviser – a ‘co-ordinating lead author’ – for the United Nations Intergovernmental Panel on Climate Change (IPCC). His statement appears to contradict Met Office chief scientist Dame Julia Slingo.
I would challenge anyone that BELIEVES they can measure sea level and then sea level rise to 0.001metre all over the planet. She is a liar. If you look at old and recent photos of beach scenes around the world you will not be able to note the difference between now and 100 yrs ago.
Martin A: Your comment is inappropriate here and should be moved to unthreaded.
Feb 16, 2014 at 8:47 AM | Registered Commenter Phillip Bratby
Phillip, don't get too pedantic. It is sometimes of great use to have such 'related' comments and links in a thread, particularly for those of use who don't get to read all the other threads.
Stephen: I disagree. Andrew Kerton's post is another example. The whole point in having Unthreaded is so that the main threads are not disrupted by completely separate issues. If people don't read Unthreaded, then that is their loss.
' this is over and above the increases associated with sinking of the southern part of the UK due to isostatic adjustment from the last Ice Age. '
People forget that it was not that long ago with did not even know this is happing , and how do they 'know' how much isostatic adjustment there 'should be ' , well they don't its guess coming from models based on other guesses and some reality.
Nice scary headline back up with little but guessing , at a time of troubled weather conditions, poor science in action but its the MET just doing its 'day job '
E.M. Smith (Chiefio) has a paper today covering errors in measurements of sea level change that is pertinent for the claims by the Met Office, especially as such errors are large in areas subject to land surface movements following the last glaciation.
The Difficulties in Using Tide Gauges to Monitor Long-Term Sea Level Change
John HANNAH, New Zealand
http://chiefio.wordpress.com/2014/02/15/gee-siting-problems-and-intrument-error-in-sea-level-gauges/
No doubt Miliband will jump on this bandwagon! and rant that the entire UK will be under water by 2050.
Thanks for this, Nic. I've also been wondering why they need to use the whole range of UKCIP projections since 1990, as they can surely rule out some by now.
There are some relevant comments and a useful graph by Tim Channon on my recent post on the Met Office report. "Met Office Report Says Sea Levels Likely to Rise 11-16cm by 2030?"
In the comments, Richard Betts explained the basis of the Met Office numbers (which were not clear in the original version of the report) and said that this implies an increase of 5 - 7 cm between now and 2030 (though I have no idea how 'official' that projection is).
I pointed out that this implies a large acceleration by 2030:
Cumbrian Lad
"paragraph 5, line 4; should that 0.1 be 0.01?"
Indeed it should; thank you for pointing this out. I was originally using mm in this paragraph and when restating everything in cm I forgot to change this figure. Apologies.
Perhaps BH could correct the figure, or put a note at the end of the article saying that the 0.1 figure is actually 0.1 mm not 0.1 cm.
Ruth Dixon
"There are some relevant comments and a useful graph by Tim Channon on my recent post on the Met Office report"
Yes indeed. I'm afraid that when writing this article (on 13 Feb) I was unaware of your post at My Garden Pond, or indeed that the version of the Met Office report that I read was not the original one.
Altogether the Met Office seem to have made a real mess about sea level rise projections. The underlying problem is that the UKCP09 climate projections are faulty, so everything based on them is unsound. The same goes for the AR5 projections, which are based on the excessively sensitive CMIP5 global climate models. But there does seem to be an additional factor, in that (absolute) sea level in most of the English Channel has been rising progressively less fast than sea level in the North Sea. I've no idea why. AR5 FAQ13.1 Figure 1 shows the shortfall over the 1993-2012 period nicely, if you enlarge it.
sandy S
As a quick and dirty source I am using the graphs from here
http://en.m.wikipedia.org/wiki/Current_sea_level_rise
For more recent changes I use
http://sealevel.colorado.edu/content/global-mean-sea-level-time-series-seasonal-signals-removed
My own interpretation is that the relatively rapid rise from 22,000 years ago is due to the warming out of the last glacial period. It took till 8000 years ago to reach equilibrium and then the rate slowed. Using this data it is hard to estimate rates between 8000BP and 1870, but 10 m in 8000 years gives 1.2mm/year. That's comparable with the late 1800s.
1870 is both the start of the Law Dome CO2 rise and the start of the sea level record. Whether the gradual acceleration seen from 1870 is anthropogenic, or a continuation of LIA recovery, or both remains an open question. Sea level changes 50mm between 1870 and 1920, 1mm/ year.
The data are fairly noisy which does not help.
The satellite data starts in 1993. This coincides with a reduction in noise level and the acceleration disappearing. Whether this is a genuine change in rate of change, or just the effect of better instrumentation is again debatable. The rate of rise is 3.2mm/year.
In summary I divide this data into three periods.
1) Pre 8000BP. 8mm/year sea level rise as the Holocene moves towards thermal equilibrium.
2) 8000BP to 1920(?)AD. 1mm/year sea level rise, with ocean and atmosphere close to equilibrium.
3) Post 1920. Sea level rise has increased in rate to 3.2mm/year due to AGW.
Future pattern? Depends on how the imbalance behaves, which is too complex for quick discussion here.
Your turn, sandy s. Do you see a different pattern in the data. How do you explain it?
Thank you, Omnologos (Feb 16, 2014 at 8:09 AM), that is an argument I, too, have been trying to raise, but not quite as eloquently as you have done. Full marks to you! (And ditto for your postscript.)
Nic Lewis
A little while ago I read a paper on the effect of the gravitational attraction of the Greenland ice sheet on the the adjacant ocean. The attraction is large enough to significantly raise the sea level within 1000 miles.
As the ice melts the attraction decreases. The curious effect is that distant sea levels rise as ocean volume increases, while sea levels closer to Greenland actually drop.
I remember that the British Isles were on the borderline. Melting Greenland's ice would have no net effect on UK sea level as the two effects would cancel out. Melting Antarctic ice would, of course, increase UK sea level.
The perversity of the universe means that I can no longer find the original paper, but the idea is still in circulation.
http://sealevelstudy.org/sea-change-science/whats-in-a-number/attractive-ice-sheets
Entropic man -
There is a nice map of the phenomenon here. However, net drop of sea level due to melting is limited to c. 1000 miles from the center of the ice loss; although nearby locations experience less-than-global-average rise. Also, Greenland ice loss represents only a fraction of the global total sea level rise.
[Ed. Luboš Motl has a derivation of the first-order correction to an equal rise world-wide.]
[P.S.S. Perhaps the paper you ere looking for is Bamber & Riva, "The sea level fingerprint of recent ice mass fluxes", The Cryosphere (2010)?]
The tide gauges along the English Channel are not showing much sea level rise at all.
Clickable zoom-in map from PMSL.
http://www.psmsl.org/data/obtaining/map.html
And the "working" GPS stations are not showing much vertical land movement either.
Clickable zoom-in map again.
http://www.sonel.org/-GPS-.html
The working GPS at Sheeness has been rising at 1.0 mm/year.
http://www.sonel.org/spip.php?page=gps&idStation=841.php
And the working one at Lowestoft is sinking at -0.61 mm/year
http://www.sonel.org/spip.php?page=gps&idStation=2027.php
Most people think southern England is sinking and northern UK is rising rapidly from glacial rebound but the GPS stations are not showing that. Not much is happening.
Entropic Man
Thanks for the links, it would make life easier if you used the a href="link" text appearing in text /a as shown below the text entry box. see here
Your quick dirty link looks to me like a fairly constant rise with both higher and lower rates. There is no way of knowing whether the current rate will revert to the mean or continue. Which reading between the lines I think you may agree with. There seems to be little correlation between CO2 and rate of increase, particularly in the satellite era. Also rising surface temperature doesn't necessarily imply rising temperature throughout the whole of the ocean or any particular part of it.
My other problem with linking the rise in sea-level to CO2 is that there is a definite lack of data on what causes changes in temperature of the oceans, how much of the oceans is warming, how much is cooling to make the calculation (of sea level change) no more than a shot in the dark. With thermal expansion and land based ice melt the change to sea level should have virtually no lag. So I still find it hard to assign the rise to man's activities.
Do you have any data on how much the oceans warmed during the first 8000 years of the current interglacial or better data on ocean temperatures over time?
This little discussion has reminded of something I heard/read/saw many years ago which suggested that one of the reasons for the Anglo Saxons crossing the North Sea was rising sea levels causing them problems in Jutland, heligoland and Frisian Islands. I'm going to have to research that now.
Your Grace
Can anyone advise me if the level of the continental land masses is sufficiently stable to be able to measure sea level relative to this accurate to a few millimetres?
Roger
Entropic Man
Any comments on the link posted by Peter Azlac?
sandy S
Chiefio rather wears his sceptic views on his sleeve."Kiss the ring", indeed :-)
The article he critiqued is basically correct. The confidence limits of the early tide guage data are considerable, and need to be treated with due caution. There is also a considerable difference in quality between the best data and the worst.
I disagree with his underlying contention that the uncertainty makes them entirely useless. Remember Newton's fourth law of inquiry, nowadays paraphraaed as "Work with the data you have".
At the bottom of this page
http://sealevel.colorado.edu/content/tide-gauge-sea-level
Is a table of sea level data derived from various analyses. You will see that they give rates of change and their calculated error bars. They are much smaller than Chiefio would have you believe.
8000-6000 years ago people were living in Doggerland - in the North Sea and Britain was joined to Holland. The Thames and the Rhine were part of the same river system draining into the English Channel. Sea levels have been rising since the last ice age and will continue to slowly rise until we enter a new glacial cycle. Sea levels during the previous interglacial 100,000 years ago were 20 meters higher than they are today. Tidal ranges of 10 meters are common in the UK so a couple of cm is nothing to get worked up about.
Sandy s
You correctly identify the rate problem. Melting ice boosts sea level immediately. A feedback driven temperature rise as seen before 8000BP may take 10,000 years to warm the entire ocean to equilibrium, with a corresponding time delay before sea level stabilises. This is part of the reason why climate sensitivity is so hard to pin down, as it can take millennia to go from TCR to ECS., even after CO2 and insolation stabilise.
As I have said before, the observed sea level changes are consistent with the physics of natural CO2/ temperature feedbacks and , more recently, cAGW. The energy budgets match. I would be interested to see good data suggesting an alternative, but nobody has published proper numbers. Until then I'll stick with cAGW as the least worst option. :-)
Regarding the link between CO2 and sea level. Between 22,000BP and 8000BP CO2 rose from200ppm to 280ppm and sea level rose by 120m.
Between 8000BP and 1920 sea level was effectively constant and so was CO2.
After 1920 CO2 rose and so dd the rate of sea level rise. The relationship may be complex, but CO2 and sea level do seem to go up and down together.
Sea surface temperatures during the Holocene probably followed Maccott et al. Deep temperatures, I' m less sure about, mainly because I'm not sure where to look.
Clive Best
A couple of cm is nothing to worry about. 20m would considerably damage our civilisation. Are you sure that a 20m rise will not occur? If you are sure, please explain why.
Entropic man,
We are nearing the end of the current interglacial and a slow cooling cycle will naturally begin within the next 1500 years. - see http://clivebest.com/blog/?p=2775 Current sea level rise is about 1.5mm/year so the maximum sea rise we could expect is < 2m before the next ice age. Levels were 20m higher during the last interglacial because temperatures were 3-4 C higher than now. The worst "realistic" scenarios for AGW are an extra 2C rise before we run out of fossil fuels anyway. There simply is not enough time for the major ice sheets to react to this and melt before natural orbital effects reassert themselves.
The next ice age is a far greater long term threat to civilization. So is a major meteor impact or even super-volcanoes. Should we also act now to avert such hypothetical threats ?
EM: your numbers for sea level rise do not agree with ipcc ar5 which gives an average rise of 1.7 mm/yr over the period 1910 to 2010 but notes the last 20 years or so might be a higher rate of 3.2 mm/yr (but with larger uncertainty). However it also notes that the period 1930 to 1950 also had a higher rate comparable to the latter part of the record and this clearly cannot be linked to AGW as you claim. You appear to be setting yourself up as some kind of authority on sea level rises, but unfortunately the analysis of the actual data by the ipcc does not agree with you.
And just to remind you about moving the goal posts, co2 effects only kick in post 1940's, not in 1920 as you imply in the following point:
"3) Post 1920. Sea level rise has increased in rate to 3.2mm/year due to AGW."
And as the ipcc itself notes in ar5, there was an acceleration 1920 to 1950, but it is not a continuous 3.2 mm/yr from 1920 to present: that is misinformation created by you.
Sorry, but no. Your claim is not true. What was co2 doing just around 1920?
And sea level rise does not follow co2, it follows temperature.
There are lots of comments about isostatic rebound or whatever. Don't the movements of the tectonic plates have any effect?
Entropic Man
What proportion of the increase in atmospheric CO2 from 200 to 280 ppm was caused by out gassing due to the rise in temperature as shown by rising sea levels, and out gassing from melting ice which as water then warms up?
Entropic Man
I did search for that Dark Age Sea level rise. I found this and this and this none of which are exactly what I was looking for but are interesting all the same.
Entropic Man
One last search before turning in found this which probably matches what I remembered.
Thinking scientist
Read the graphs I linked. That's where I pulled the numbers.
Thank you for the IPCC figures. One of the pleasures of doing science for fun is seeing how close one can get to the professionals using the raw data and ones own wits.
Clive Best
The next ice may be as far as 50,000 years away. In the meantime there are lots of high risk events to keep an eye out for. Remember that risk is likelihood* damage.
Dizzy Ringo
Yes, tectonic movements can have a considerable effect. If you use that link in Peter Azlac's post and read the report, you'll see the author (John Hannah) insists that sea level data from anywhere so affected should not be used. A dictum honoured more in the breach than observance.
I started digging into SLR a few years ago. The further I got the more shortfalls I saw in the way data are collected. There are just so many ways in which establishing a correct datum can be undermined. And as Hannah mentions, that includes satellite altimetry because it has to be calibrated from a a terrestrial datum.
Sandy s
There is not much CO2 in ice. The big carbon sinks are ice and dissolved gas in the oceans.That is where the CO2 was released into the air as the Holocene warmed.
11mm/year at the start of the Holocene! That's way more than I estimated.
The Amsterdam graph is illuminating. The sea level rise started around 1800. Good evidence for your LIA recovery hypothesis.
The earlier pattern looks pretty static. Score one for me?
I grew up on the edge of the Fens. They are now like the Somerset Levels. Peat shrinkage has lowered the land below sea level and below the drainage channels (confusingly we called them dykes). It can feel odd to drive along looking up at the boats. Hope the pumps keep working :-)
Harold W
Thank you. Bamber & Rica was what I was looking for. Do not tell the politicians about this. They would get even more confused. :-)
Sandy s
Make that "The big carbon sinks are tundra and dissolved gas in the oceans"
The senior moments are becoming continuous. :-)
Thank heaven for GPS. It has made a big difference to the quality of tide gauge data by removing a lot of the position, height and movement uncertainty.
Entropic Man
We've about reached the end of my limited knowledge, just a couple of things to add to the mix. Some of the data agrees with what you said, I didn't think it wouldn't. The melting of large quantities of ice adding water at ~0'C which then warmed to ~10'C must have had an interesting effect on atmospheric CO2; decrease then an increase with no other inputs? I wouldn't be prepared to guess how much though, modern technology and access to raw data will enable us to get a handle on exactly what is happening to sea levels, although as natural cycles are involved and data is very noisy it will probably my grandchildern's generation who have the first chance to have anything meaningful to work with.
Thanks for the civilised discussion, I'll come back with more if/when I have anything or a thread throws up something,
BTW glad you've sorted, at least partially, your posting issues as I do follow your links. A lot of the sceptical ones I've seen by the time Ihey appear here. Although I will still complain if I think they are not what you think they are.
Final aside I grew up in Central Perthshire and at the bottom of virtually all peat bogs are tree stumps. The worst erosion is caused by humans doing dumb things. Taking peat for domestic consumption at traditional locations had little knock damage. On the other hand building access roads created issues lasting decades.i remember reading a number of years ago that agriculture in the fens was in danger of running out of soil due to loss of the topsoil, not entirely sure that wasn't hyped research.
Entropic man: "Do not tell the politicians about this. They would get even more confused. :-)"
Call me cynical, but I am doubtful this is possible. At least among U.S. politicians, confusion is not the problem -- it's oversimplification. [And I don't mean to restrict this to one "side" -- I hate even the description of this as a two-sided tug-of-war.] There is a positive-feedback effect -- much like confirmation bias -- which tends to ensure that nobody changes his mind due to additional evidence. Only political ambition would seem to have enough energy to overcome that barrier, allowing a politician's opinion to tunnel from certainty on one "side" to certainty on the other. The intermediate states are not stable.
I've seen it suggested that the drowning of Doggerland and indeed many Diluvian or Atlantean myths stem from sudden rises associated with large ice dams breaking in the wake of the Ice Age.
Do these theories have any credibility and if so do estimates of gradual sea rises account for them?
Sandy s
A civilised debate is always a pleasure. I hope we have many more.
The melting ice adds 3*10^-5% per year to the ocean volume. That increases the sea level by 1.4mm/year, but unfortunately has little effect on its capacity as a carbon sink.
Reduced salinity may have some effect. Dr. Curry recently published a paper suggesting that the increased Antarctic sea ice extent was due to dilution by meltwater from the land. This increases the freezing temperature of the Southern ocean.
<a href=""http://m.pnas.org/content/107/34/14987.full""
The Irish bogs also have tree stumps and preserved wood in them, known as bog oak. There's a grandfather clock in work. The case is made of Irish bog oak exported to Chicago by some sentimental emigrant in 1904.
From the climate viewpoint, there was a temperate and relatively dry period in the UK early in the Holocene. Temperate woodland grew for a while, before the climate got too wet and the bogs took over. If your lawn is growing sphagnum moss and trying to turn into a bog, you'll know why. Mine has gone beyond retrieval, but then I already live in the second wettest spot in Britain.
Harold W
The drift to extremes seems universal. In Northern Ireland the moderates have declined. The two extreme parties, Sinn Fein and the DUP, are now running the government.
Kelly down
The best candidate I've heard of is the rapid inundation of the Black Sea when the Mediterranean broke through the Bosphorus about 5600BC.
http://www.pbs.org/saf/1207/features/noah.htm
Entropic man -
Fascinating story about the Black Sea, new to me. Thanks!!