Guest post by Steven Goddard
One of the most cited “proofs” of global warming is that sea level is rising, as can be seen in the graph below.
http://sealevel.colorado.edu/current/sl_noib_global_sm.jpg
This is a nonsensical argument, because sea level would be rising even if temperatures were going down, as they have been since 2002. The main reason why sea level rises is because the equilibrium between glacial ice and temperature is out of balance, and has been for the last 20,000 years.
http://www.globalwarmingart.com/wiki/Image:Post-Glacial_Sea_Level_png
Note that from 15,000 years ago to 8,000 years ago, sea level rose about 14mm/year – which is more than four times faster than the current rise rate of 3.3mm/year, as reported by the University of Colorado. During the last ice age, sea level was so low that people were able to walk from Siberia to Alaska across the Bering Strait. One of the more stunning pieces of evidence of this is the remarkable similarity of appearance and culture between the indigenous peoples of Eastern Siberia and North America.
In 2002, the BBC reported that a submerged city was found off the coast of India, 36 meters below sea level. This was long before the Hummer or coal fired power plant was invented. It is quite likely that low lying coastal areas will continue to get submerged, just as they have been for the last 20,000 years. During the last ice age, thick glaciers covered all of Canada and several states in the US, as well as all of Northern Europe. As that ice melts, the water flows into the ocean and raises sea level.
http://uk.encarta.msn.com/media_461527006/ice_extent_during_the_last_ice_age.html
The IPCC has stated that sea level may rise two meters this century, which would be a rate of 22mm/year, nearly seven times faster than current rates. Do we see such an acceleration? The simple answer is no. There has been very little change in sea level rise rates over the last 100 years, certainly nothing close to the immediate 7X acceleration which would be required to hit 2 meters.
Sea level is rising, and the abuse of this information is one of the most flagrantly clueless mantras of the alarmist community.
Even if we returned to a green utopian age, sea level would continue to rise at about the same rate – just as has done since the last glacial maximum.
Tom P.,
Hence the satellite-derived current rate of 3.3+/-0.4 m a year is at least three times the background level…
That should read mm/year otherwise that would be a 3,000 fold increase over background.
Steven,
I don’t think you can establish a natural background prior to any possible anthropogenic contribution by looking at the data from 1880 to the present. The Holocene sea-level rise rate dropped dramatically 7000 years ago from 14mm/year to 0.4+/-0.4 mm/year. I see no justification for comparing the current rate of sea-level rise of 3.3mm/year to the rate before 7000 years ago when there is just an accurate rate that can be used for the last few thousand years.
The plots you show contradict the point you are trying to make.
Tom P,
I looked closer at the Holocene graph you linked and thought it needs further comment. The drawn linear inflection point at 2,000 YBP is complete statistical nonsense. That is the kind of garbage which keeps AGW alarmism alive.
Tom P (07:32:57) :
Steven,
The background sea-level rise can be extracted from http://www.globalwarmingart.com/images/1/1e/Holocene_Sea_Level.png. The fit on this plot is shown as currently flat, but there is considerable scatter in the data. At a stretch the rate over the last six thousand years might be at most a rise of 1m/millennium.
And the explanation for those sunken cities and settlements is?
Which do you trust more – proxy reconstructions or concrete archeological evidence?
Your basic logic seems to be letting you down here.
To anyone interested in sea level changes and global lithospheric response, this paper is a must read and still a reference today:
J.A. Clark, W.E. Farrell and W.R. Peltier, Global Changes in Postglacial Sea Level_ a Numerical Calculation, Quaternary Research, 9, 265-287, 1978
Fascinating discussion – I keep following all the links and have managed to avoid my real work for about 4 hours as a result.
As a dam designer/hydro engineer, I have worked with many of the best engineering and pure geologists in the world.
I do not know any geologist who is an “alarmist”, although there are some who concede that CO2 may me marginally contributing to the warming seen over the past 200 years.
I thank my geologist colleagues for imparting to me a better understanding of processes and enabling me to reserve judgement on the AGW hysteria.
It’s tempting to think of that (comparitively) sudden rise in sea level as the source of the flood legends.
A bit of historical fiction that features a different sea level for the English Channel is The Forest by Edward Rutherford.
The town I grew up in, where my grandparents have lived for over 90 years, has a section of fill and lagoons that is at sea level. The waves still arch over the sea wall only in really big storms at peak high tide and the one low bit of roadway floods only at those times. We have always joked about what will happen when the glaciers melt, but so far the empirical evidence, for our town anyway, is that sea level isn’t changing much.
Steven Goddard (07:57:49) :
The Earth has some elastic compressibility, so it doesn’t necessarily have to rise else where if you depress it in one spot. You are correct in pointing out the decreased mass of the ocean, but it is spread out over the entire ocean (roughly 3/4 of the earth) vs concentrated in ice in smaller areas. This change in stress is diffused over a large area, so the relative effect isn’t as great. Also, you are dealing with oceanic crust vs continental crust, which the most significant factor. Ice is is loading continental crust & lower ocean levels are de-loading oceanic crust. Continental crust is far more buoyant on the mantle than ocean crust (which of course is why ocean basins are low points on Earth start with). Because oceanic crust is less buoyant, changing the load on it has less spring effect on it & vice versa. So, in short, it is not a wash due to non-homegeneous properties of the earth (compositionally & aerially) & the elastic properties of the earth.
Sea levels are a fluid affair (pun intended) and a rise in one place is often matched by a fall in another, so information has to be heavily averaged, smoothed, interpreted, interpolated, sent through all sorts of computer models and emerges as pretty useless.
There are some obvious factors that need to be considered, such as a high or low pressure weather system at time of measuring, together with the state of the tide-both within its twice daily cycle and also within the longer lunar cycle. Add waves of varying sizes and thermal expansion, and it becomes extremely difficult to measure to the ocean surface-wherever that may be at any one time.
Satellite drift and the averaging already mentioned create further problems and account must be taken of obstructions such as new docks, build up of sand bars, the nature of the sea bed and the stasis of the land-is it rising, falling, or static?
Officially satellites are accurate to within plus or minus 3cm or so (yes 30-50mm) unofficially probably double that level of inaccuracy which is all smoothed out of the final data.
The following sites give a good description of the process-which is being constantly refined but doesn’t get more accurate as the inherent flaws in measuring capabilities can’t be resolved.
http://www.tos.org/oceanography/issues/issue_archive/issue_pdfs/15_1/15_1_jacobs_et_al.pdf
http://jchemed.chem.wisc.edu/Journal/Issues/1999/dec/abs1635.html
The following site deals with problems of the data;
http://www.climateaudit.org/?p=859
This with reliability
http://lightblueline.org/satellite-tracking-sea-levels-set-launch
The UK Environment Agency like to use physical tide gauges as well, which are both visually observed or can send data electronically. Best of all is gathering information from local people such as the Harbour master or those who work the fishing boats as they know what the sea height is doing (generally nothing much)
Sea level rises are being hugely exaggerated. In many places they are actually falling as per Newlyn UK.
http://tidesandcurrents.noaa.gov/sltrends/resids/170-161.gif
and Helsinki. http://tidesandcurrents.noaa.gov/sltrends/resids/060-351.gif
and generally around the Baltic coast.
Others are rising modestly- so the two above are cherry picked as illustrations- but show the rises and falls over decades rather well.
The worlds leading sea level expert Professor Morner has called the IPCC figures ‘a lie.’
The following link leads to a graph produced by the Dutch Govt sea level organisation-the Dutch certainly know a thing or two about the subject and confirm sea levels are stable and are somewhat lower now than during the MWP.
http://www.climateaudit.org/?p=61
This is confirmed by various UK studies-allowing for the various factors mentioned- such as the research done on the entrances to British castles which could formerly be accessed by sea when first built, higher rivers which the Vikings used to their advantage in sacking inland cities in Europe, old battle sites etc.
TonyB
From the IPCC:
“Geological observations indicate that during the last 2,000 years (i.e., before the recent rise recorded by tide gauges), sea level change was small, with an average rate of only 0.0 to 0.2 mm yr–1 (see Section 6.4.3). The use of proxy sea level data from archaeological sources is well established in the
Mediterranean. Oscillations in sea level from 2,000 to 100 yr before present did not exceed ±0.25 m, based on the Roman-Byzantine-Crusader well data (Sivan et al., 2004). Many Roman and Greek constructions are relatable to the level of the sea. Based on sea level data derived from Roman fish ponds, which are considered to be a particularly reliable source of such information, together with nearby tide gauge records, Lambeck et al. (2004) concluded that the onset of the modern sea level rise occurred between 1850 and 1950. Donnelly et al. (2004) and Gehrels et al. (2004), employing geological data from Connecticut, Maine and Nova Scotia salt-marshes together with nearby tide gauge records, demonstrated that the sea level rise observed during the 20th century was in excess of that averaged over the previous several centuries.
The joint interpretation of the geological observations, the longest instrumental records and the current rate of sea level rise for the 20th century gives a clear indication that the rate of sea level rise has increased between the mid-19th and the mid-20th centuries.”
So, before you can claim that “sea level would continue to rise at about the same rate – just as has done since the last glacial maximum” you have to show why you think the IPCC is wrong about sea level rise rates for the last 2 millennia. The last 100 years _have_ been anomalous in the past several thousand.
“The IPCC has stated that sea level may rise two meters this century”: Really? I thought the IPCC upper bound was 59 cm, plus possible additional amounts from dynamical changes in ice sheet flow that they chose not to quantify. Other authors have hypothesized a possible 2 meter rise – Pfeffer et al, for example, got 2 meters if they assumed that every dynamical uncertainty was resolved in the pessimistic direction, 80 cm with more reasonable assumptions.
In any case, pretty basic physics indicates that _IF_ temperatures increase, the rate of sea level rise will increase compared to the case without temperature increases. I suggest that you go back and restudy some of your “Basic Geology”.
So you state that “abuse of this information is one of the most flagrantly clueless mantras of the alarmist community” and then you draw your own conclusions from HALF A CYCLE of data?
You also state that “There has been very little change in sea level rise rates over the last 100 years” referring to the Recent Sea Level Rise chart. However comparing the first 60 years (~5 cm rise) to the next 60 years (~15 cm rise) tells a different story.
Have you ever shared your scientific credentials with us? Other than your “guest posts” here, all I can find through Google are a few climate posts on a UK technology site that appear to conclude with a retraction. (I happen to have a B.Sc. in Geology from the University of Toronto.)
ps. Tallbloke: “And the explanation for those sunken cities and settlements is? Which do you trust more – proxy reconstructions or concrete archeological evidence? Your basic logic seems to be letting you down here.”
If you read the BBC news piece, it notes that the sunken city is dated to more than 9000 years in the past. Basic logic can be applied to show that a claim of <1 mm rise for the last several thousand years can be perfectly consistent with your concrete archeological evidence if your concrete evidence comes during the time period that alarmists and skeptics alike agree was having extremely large SLR changes.
Er. That should have been <1 mm rise/year, not <1 mm rise absolute in my last post.
Jeff L,
The density of the continental crust vs. oceanic crust shouldn’t make any difference to this analysis, because it is changes in water thickness, not crust thickness we are talking about.. The total weight of water is more or less fixed, whether in solid or liquid state, and will on average have the same net global effect on compressing the mantle, regardless of the particular distribution of ice at the time.
Marcus,
You might want to check your math. The city is currently 36,000 mm below sea level. Over 9,000 years that averages to 4mm/year.
Steven Goddard:
The seal level is still slowly rising, because the planet is still emerging from the last Ice Age. AGW has nothing to do with it. That is made clear by the failure of AGW proponents to provide any real evidence showing that AGW causes the sea level to rise.
Steven,
You state:
“The drawn linear inflection point at 2,000 YBP is complete statistical nonsense. That is the kind of garbage which keeps AGW alarmism alive.”
I’m not using the trend line to make my point, but the data points to derive my upwards slope of 0.4+/-0.4. There is no statistical basis for plotting a line of 3.3+/-0.3mm a year through the data. If you think there is, perhaps you could show the plot. You actually have posted, without obviously realising it, one of the strongest pieces of evidence for an anthropogenic warming, a rapidly increasing sea level for the last one hundred years way beyond anything seen in the last 7000 years.
Tallbloke,
You state: “And the explanation for those sunken cities and settlements is?
Which do you trust more – proxy reconstructions or concrete archeological evidence?
Your basic logic seems to be letting you down here.”
If the data that Steven published can’t be trusted, why do you think he posted it? He thought it proved his point – and you certainly didn’t express any doubts about the data until I pointed out it actually indicated the exact opposite.
Robert Woods says:
You might be tempted to think so. I think it more likely that those legends are a result of the Sea of Marmara breaching the Bosphorous around 5600BCE.
Tom P says:
What is the mechanism? How is anthropogenic warming connected to sea warming.
Ben Lawson,
Over the past 100 years, going back to the invention of the automobile, sea level has risen at an average rate of 2mm/year, pretty close to current rise rates of 2.4mm/year as reported by Aviso, and much less than the average during the interglacial.
http://www.globalwarmingart.com/images/thumb/0/0f/Recent_Sea_Level_Rise.png/700px-Recent_Sea_Level_Rise.png
http://www.aviso.oceanobs.com/fileadmin/images/news/indic/msl/MSL_Serie_J1_Global_NoIB_RWT_PGR_NoAdjust.png
I have B.S. in Geology and many years professional experience. Are you trying to suggest that sea level has not risen nearly continuously since the peak of the last ice? Good luck with that theory, geologist. My advice is don’t write a paper on it.
http://www.globalwarmingart.com/wiki/Image:Post-Glacial_Sea_Level_png
Steven,
You state “You might want to check your math. The city is currently 36,000 mm below sea level. Over 9,000 years that averages to 4mm/year.”
You might want to check your plot – this city’s 36m depth sits right on the sea-level data trend you posted. And that data shows the rate slowing to well below 4mm/year 7,000 years ago. To derive your linear trend value from a single data point you have to ignore the very data you presented.
Tom P:
Wrong.
Sea levels are not currently rising: click
That statement is confirmed by the leading international expert on sea level changes: click
If the sea level was actually rising faster than average since the last Ice Age — or even rising noticeably — there would be confirmation by endless front page, above the fold news reports.
The fact that the mainstream media isn’t red faced, spittle-flecked and arm waving over the sea level tells you all you need to know about it.
[For a gif showing sea level anomalies from 1997 through 2008: click. Notice that except for the unusually warm 1997/98, the sea level during most years has been flat to declining.]
Tom P,
State something specific or cut the ad hominem attacks.
CO2 levels have only been rapidly increasing for the last 50 years or so. Don’t try to blame rates from 100 years ago on your neighbor’s Hummer.
Sea level normally goes down at the beginning of the year. Data from the first image from colorado.edu used to be available in almost real-time in the past, but now it lags behind. Is something not being shown?
Another interesting question is where was the sea in the Medieval Warm Period. We have empirical evidence in Portugal where history might put the sea some 3/4 metres above what it is today. If someone has got issues/ideas to exchange on this domain, please email me.
Ecotretas