Recent Sea-Level Change at Major Cities

Guest essay by Rich Taylor

Abstract

Human population is becoming increasingly urban, and most of the world’s largest and fastest-growing cities border tidewater. This note presents charts of annual-value (AV) tide-gauge records in or near major coastal cities to illustrate the sea-level change these cities have observed recently, and fits linear trends to the records. Trends range from -1.5 mm per year (mm/y) to 18 mm/y. Tectonic uplift can explain the lowest trends, and cities growing rapidly on unconsolidated sediments (perhaps dredged) have the highest trends due to land subsidence. Urban areas that encompass ground of variable stability observe variable sea-level change. Where the ground is stable, typical change appears to be a rise of 1- to 2-mm/y. Rates above 3 mm/y seem to have a substantial component of natural and/or anthropogenic subsidence. Rates above 10 mm/y appear to be a primarily a consequence of human activity, which implies they should be manageable to some degree.

All records in this review are from the website www.psmsl.org of the Permanent Service for Mean Sea Level. Profound thanks are due to the Service and its supporters; the website makes it easy to find and download data of apparent fidelity. All geological information is from the website mrdata.usgs.gov/geology/worldgeol.html of the US Geological Survey. The website presents world geology compiled by the Geological Survey of Canada (Open File 2915) as an interactive map that is easy to navigate and interrogate.

Trends in long records

A few major coastal cities have tide-gauge records that exceed 100 years in length. Records that are sufficiently long and accurate show the transition from stable sea-level that prevailed during the 1800s to the general rise that has been characteristic since about 1900. AVs from the gauge at the small city of Brest show this history clearly.

Brest is on terrane that is mainly sedimentary, which rests on older metamorphic and plutonic rocks that outcrop within 20 km to the north and south. Sedimentary rocks can be porous, and they decompose more readily than plutonic and metamorphic rocks into unconsolidated sediments. Plutonic and metamorphic rocks are typically non-porous. Unconsolidated and consolidated sedimentary terranes are more prone to land subsidence, especially when pore-fluid such as groundwater or natural gas is extracted for some combination of civic, industrial or agricultural use. Volcanic rocks have variable porosity and durability.

Brest has the longest record in the regular PSMSL database, and the record has good continuity and quality. From 1807 to 1900, AVs at Brest suggest sea-level was essentially stable. The trend for the last 100 years has been 1.5 mm/y, likely due to thermal expansion of sea water and the net transfer of water from continental aquifers to the ocean.

clip_image002Accordingly for major cities with long records, AVs are used that provide a trend as close as possible of 100-years-to-the-present, and the rest of the AVs are presented but not trended.

An alphabetical review follows of the most populous coastal cities.

Bangkok harbor is the site of the Fort Phrachula Chomklao gauge. It is in the delta of the Chao Phraya River, which rests on mainly sedimentary terrane. From 1940 to 1959 (B59) its trend was 2.7 mm/y. Since 1962 (B62) it has been 18 mm/y (i.e. 18 cm/decade). The gauge has data-quality cautions (QCFLAGs) for the sharp increase in trend from 1962 and an apparent datum shift from 2003.

Sixty km to the south-southeast in the Gulf of Thailand is sparsely populated Ko Sichang Island and its gauge. The island is near the boundary where sedimentary bedrock rests on older plutonic terrane. From 1940 to 2002, the trend of the gauge (KS) was 0.8 mm/y. The Ko Sichang trend suggests that most of the apparent sea-level rise at Bangkok to 1959 is due to land subsidence, and that urban activity since 1962 has made the rise about 7-times more rapid than before and about 20-times more rapid than on Ko Sichang.

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Unconsolidated sediments, such as in Bangkok harbor, are prone to subsidence but gauges in the Netherlands show that stability can result from planning and management. The Maassluis gauge has the longest record; it sits about 15 km from the North Sea on the Maas channel that takes most of the flow through the Rhine (etc.) delta. Its 1.8-mm/y trend is also the average 100-year trend of the six long-standing gauges (Vlissingen, Maassluis, Hoek van Holland, Ijmuiden, Den Helder, Harlingen and Delfzijl) that monitor sea level for the Netherlands.

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Buenos Aires is on mainly sedimentary terrane bordering the Rio de la Plata estuary. Its Buenos Aires gauge provided AVs from 1905 to 1987, and the nearby Palermo gauge provides AVs to the present. Both have trends of 1.6 mm/y.

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Chennai is on mostly sedimentary terrane, near the surface contact with underlying metamorphic/plutonic terrane. The trend at the Chennai / Madras gauge from 1916 to 2010 was 0.6 mm/y.

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Guangzhou, Dongguan, Shenzhen, Hong Kong (HK), Macau and Zhongshan encircle the Pearl River Estuary (Shiziyuan). This area is on mainly sedimentary bedrock, but underlying plutonic terrane outcrops in the northern part of Guangzhou and in Macau. There are nine gauges in HK and in one in Macau that have operated during the last 100 years, which allow an insight into intra-urban variability. In order of initial AV, the following table and chart summarize information provided by these gauges.

Gauge Span of AVs Trend mm/y AVs / Span Chart Legend
Macau 1925-1982 0.2 58 / 58 M
North Point 1950-1985 -1.2 35 / 36 N
Chi Ma Wan 1961-1989 1.8 15 / 29 C
Tai Po Kau 1963-2016 3.1 50 / 50 P
Tsim Bei Tsui 1975-2016 0.6 27 / 42 T
Loc On Pai 1986-1998 -1.1 10 / 13 L
Quarry Bay 1986-2016 2.9 31 / 31 Q
Waglan Island 1995-2015 4.0 13 / 21 W
Shek Pik 1998-2016 0.1 17 / 19 S
Tai Miu Wan 1998-2016 2.9 16 / 19 MW

clip_image012 In this close cluster of gauges, diversity remains in some trends that span similar intervals. A trend of 1.3 mm/y for this urban area can be obtained by averaging the trends for the gauges, where each trend is weighted by the number of years spanned by the gauge.

Hangzhou is at the south end of the Grand Canal of China in the south-central part of the Yangtze River Delta, and is underlain by sedimentary and volcanic bedrock. It has no gauge in its urban area; the Kanmen and Lusi (discussed with Shanghai) gauges are each about 300 km away. The Kanmen gauge is on volcanic terrane; its trend since 1959 is 5.6 mm/y.

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Istanbul is on mixed sedimentary and volcanic bedrock. The nearest indicative gauge might be at Alexandroupolis about 400 km to the east, on mainly sedimentary bedrock. From 1969 to 2014, the Alexandroupolis trend has been 2.6 mm/y.

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Jakarta is on mainly sedimentary terrane. It has no gauge in its urban area (and no gauge in Indonesia has more than 8 AVs in its record). Jakarta sits over a sea-floor subduction zone; Lima (q.v.) is in a similar tectonic situation and has a gauge in its urban area.

Karachi is on mainly sedimentary terrane. Intermittent measurements at its gauge from 1916 to 2014 provide a trend of 1.9 mm/y.

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Kolkata is in the western Ganges Delta on mainly sedimentary terrane. Its Calcutta gauge has a QCFLAG for an apparent datum shift starting in 1976; its trend since 1932 is 6.9 mm/y. The Diamond Harbour gauge is 40 km further south on the delta; its trend since 1948 is 4 mm/y.

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Lagos is on mainly sedimentary terrane. It has no gauge but the Takoradi and Tema gauges, respectively 700 km and 500 km to the west on the same terrane, might provide some indication of sea-level change there. The Takoradi trend from 1930 to 2008 was 2.8 mm/y, excluding AVs from 1972 and 1991 with a QCFLAG for irregular appearance. The Tema trend from 1963 to 1981 was 1 mm/y.

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Lima sits on mainly volcanic terrane above the subduction of Pacific sea-floor under South America. Its harbor gauge, Callao 2, has a QCFLAG for many ad hoc datum adjustments made to original data. The trend of the adjusted AVs at Callao 2 since 1970 is -0.3 mm/y. The La Libertad II gauge in Ecuador and the Antofagasta II gauge in Chile sit above the same subduction, have longer records than Callao 2 and neither has a QCFLAG. Their trends, respectively, are -1.3 mm/y for 1950 to 2002 and -0.8 mm/y for 1946 to 2015.

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London and area are on mainly sedimentary terrane. The Tower Pier gauge provided urban data from 1929 to 1982 with a trend of 1.7 mm/y. The Southend gauge is 50 km east in the Thames Estuary, and its trend from 1933 to the present is 1.3 mm/y.

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The Los Angeles gauge is on mainly sedimentary terrane, as are the Santa Monica. Alamitos Bay Entrance and Newport Bay gauges in the Los Angeles urban area. Santa Monica and Newport Bay are near the outcrop of underlying metamorphic and/or plutonic terrain. The trends in mm/y of the gauges are, respectively, 1, 1.5, 1.6 and 8, and the span-weighted average is 1.7.

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Manila is on sedimentary and volcanic terrane. The Manila gauge has QCFLAGs for river discharges and land reclamation. The gauge was moved in 2002. The trend (M62) from 1902 to 1962 was 1.6 mm/y. Subsequently the trend (M63) increased abruptly and has continued to the present at 15 mm/y. The Cebu gauge, 600 km to the south-southeast, is on similar terrane, has a record of comparable length and no noted adjustments or disturbances. Its trend since 1936 has been 1.2 mm/y.

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Mumbai is on Deccan basalt, a volcanic rock that typically has low porosity. The trend of the Mumbai / Bombay gauge from 1911 to 2010 was 0.9 mm/y.

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Nagoya is on mainly volcanic terrane. There is a non-specific QCFLAG for the Nagoya gauge, but the pattern seen in the combined AVs for Nagoya and Nagoya II is similar to that seen at the Onisaki gauge, on the same terrane 20 km to the south. Tectonic movement is a likely cause of the pattern. Since 1963, the Onisaki trend is -1.5 mm/y.

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The New York gauge is on mixed sedimentary-volcanic terrane, as are the Bergen Point gauge on Staten Island and the New Rochelle gauge north of the Bronx. Gauges on the mainly sedimentary terrane are Willets Point, Kings Point, Port Jefferson, Montauk and Plum Island on/by Long Island and Sandy Point off the south shore of New York Bay. USGS Fact Sheet-165-00 mentions subsidence at New York Bay.

In order of initial AV, the following table and chart summarize information provided by these gauges.

Gauge Span of AVs Trend mm/y AVs / Span Chart Legend
New York 1917-2016 3.1 97 / 100 NY
Willets Point 1932-1999 2.4 65 / 68 WP
Sandy Point 1933-2016 4.1 80 / 84 SP
Montauk 1948-2016 3.1 58 / 69 M
Plum Island 1958-1967 -4.4 8 / 10 PI
New Rochelle 1958-1981 0.6 21 / 24 NR
Port Jefferson 1958-1990 2.2 31 / 33 PJ
Bergen Point 1985-2016 4.8 25 / 32 BP
Kings Point 1999-2016 5.3 18 / 18 KP

clip_image010[4]The span-weighted average of the trends is 3.0 mm/y. Given the diversity of trends among gauges and changes in gauge activity, the long-established New York and Montauk gauges, respectively at the southern tip of Manhattan and the eastern end of Long Island, appear to be good indicators for this urban area.

Osaka is in the delta of the Yodo River, which is underlain by volcanic terrane. In its urban area are the Osaka, Kobe and Kobe II gauges, and each has a QCFLAG for subsidence. The trend of the Osaka gauge since 1965 is 5.2 mm/y.

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Qingdao has no gauge in its urban area; its coastal portion is on metamorphic and/or plutonic terrane. The Shijiusho gauge, 100 km to the southwest, is on the same terrane. The Yantai gauge is 200 km to the northwest, on plutonic terrane and has a QCFLAG for possible datum shifts. From 1954 to 1994, the Yantai trend was -0.2 mm/y and the Shijiusho trend from 1975 to 1994 was 1.7 mm/y.

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Rio de Janeiro is on metamorphic and/or plutonic terrane. The Rio de Janeiro gauge provided 13 AVs from 1950 to 1967, with a trend of 3.7 mm/y. Since 1965, the trend for the Ilha Fiscal gauge has been 1.8 mm/y. The span-weighted average is 2.3 mm/y.

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São Paulo has no gauge in its urban area. The closest gauge is Cananeia, 200 km west-southwest, which has QCFLAGs for its anomalous trend of 3.8 mm/y. São Paulo and the gauges at Rio de Janeiro 350 km east-northeast are on the same metamorphic and/or plutonic terrane so the Rio de Janeiro average of 2.3 mm/y might be also indicative for São Paulo.

Seoul is on metamorphic and/or plutonic terrane. Its urban area extends to the coast at Incheon, where the trend of that gauge since 1960 is 1.3 mm/y.

clip_image018[4]Shanghai is in the north-central Yangtze River Delta, as is the Luci gauge 100 km north of the city centre. Both are underlain by mainly sedimentary terrane. There is a non-specific QCFLAG for the gauge, where the trend since 1969 is 5.6 mm/y.

clip_image020[4]Shantou has no gauge in its urban area, but it and the Xiamen gauge 200 km to the northeast are both on plutonic terrane. The trend at Xiamen from 1954 to 2003 was 1.1 mm/y.

clip_image022[4]

Tianjin hosts the Grand Canal of China, in the Hai River delta on mainly sedimentary terrane. The trend of its Tanggu gauge from 1975 to 1994 was 5.6 mm/y.

clip_image024[4]Tokyo is on mainly sedimentary terrane where the Sumida and Tama Rivers reach tidewater. The Tokyo I gauge provided a few scattered AVs from 1958 to 1962. The Sibaura and Tokyo III gauges in combination provide AVs from 1961 to the present, and the trend of both gauges is 1.6 mm/y.

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Summary

Most of the world’s largest coastal cities border the Pacific Ocean. In recent decades, apparent sea-level has dropped at Nagoya, Lima and perhaps Jakarta. Sea level has likely risen 1- to 2-mm/y at Qingdao, Shantou, Guangzhou-Shenzhen-HK, Seoul, Tokyo and Los Angeles. It has apparently risen 5- to 6-mm/y at the delta cities of Osaka, Tianjin and Shanghai-Hangzhou. The effect of urban activity is clear in apparent rises of 15 mm/y at Manila and 18 mm/y at Bangkok.

For the Atlantic Basin, sea level has likely risen about 2-mm/y at Buenos Aires, London and Rio de Janeiro. Perhaps any change at São Paulo or Lagos has been similar. The apparent rise at Istanbul might be more than 2 mm/y, and apparent rise of 3 mm/y at New York might be due in part to subsidence.

For the Indian Ocean, sea level has likely risen 0.5- to 2-mm/y at Chennai, Mumbai and Karachi. The delta city of Kolkata has seen an apparent rise of 7 mm/y.

Delta cities and others on unconsolidated sediments have higher apparent rises. However, gauges in the Netherlands show that sea-level change in highly developed regions on unconsolidated sediments can be kept close to change seen generally around the world.

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152 thoughts on “Recent Sea-Level Change at Major Cities

  1. The readings on the tide gauge at Fort Denison in Sydney Harbour are as below http://www.bom.gov.au/ntc/IDO70000/IDO70000_60370_SLD.shtml
    This is tabular, not graphical, but does not look in any way dangerous. The change since 1914, on an eyeball, looks like a flat line.
    There has been a lot of building around this site.
    The daily tide overwhelms any absolute rise in its variation.

    • note the tide gauge data at Fort Denison was kept secret and ignored when councils used models to plan and restrict coastal development on the east coast of Australia a few years back. This policy was later scaled back or overturned. Tim Flannery’s waterfront was not affected.

      • The councils’ policies of restricting waterfront development was more of a green propaganda stunt to try and influence climate conference decisions. They were obviously not science based.

      • It would be nice if once in a while people used standard units when they are plotting graphs.

        It’s bad enough that we have to put up with Temperature anomalies, instead of real world Temperatures like thermometers measure.

        … y = a.x + b conveys NO information without units.

        Some people like to use the SI system of units; that seems quite popular, specially in France.

        Graphs are just BS without units.

        HP’s time and frequency standards lab used to have two Cesium atomic clocks in it; (HP built).

        They needed two because the US Naval observatory time was different from the NBS (now NIST) standard time, so they had one for each.

        According to the US Navy, the universe was one day older than NBS said it was.

        HP was proud of the fact that they (and almost nobody else) could tell the difference (parts in 10^13).

        One of them drove a big 12 inch diameter analog clock. The clock had three hands; but all of the numbers had fallen off the face, and were in a pile at the bottom of the front window.

        it was still there when I wa working at Agilent, but I have no idea where it is now.

        Units are useful.

        G

      • Don’t think for one minute that agencies such as OEH ( Office of Environment & Heritage NSW ) in Australia have given up, coastal property is still very much under attack. The NSW Liberal government is running a secret task force that reports to the Office of Premier & Cabinet titled “Coastal Boundaries inter-agency working group” investigating coastal land tenure and boundary change. All efforts to obtain information on the groups reports are rejected on grounds of “cabinet confidentiality” and the NSW governments Coastal SEPP 2016 seeks to impose planned retreat with the imposition of time limited development consent while concurrently removing the rights of property owners to protect property from erosion and storm. The Greens are well and truly entrenched in government bureacracy.

    • Yes, but what I want to know is what has been the historical sea level change for Kathmandu ??

      g

    • Coastal subsidence from groundwater pumping, heavier building compaction, flood control, increasing pavement stopping rewatering of sediments. That is not sea level rise.

    • Richard 2:08

      Regarding those large dams:

      Seems someone did a study and came to the conclusion that there was not much effect on sea level. I can’t remember where I read that, however.

      Of interest is that many of the reservoirs are used for irrigation water.
      Put in the coordinates below to Google Earth search:

      46.766, -119.55

      This takes you to a canal in a near desert.
      Back off (zoom out) until you begin to see green crop circles. Then continue until you have an eye elevation of about 130 miles.
      Apples, pears, …, grapes are grown here. Also hay** and vegetables.
      Almost all of these water-laden products (incl. wine) are shipped out of the growing area, and much is shipped out of the country.
      We export water!

      **hay has about 10-15% moisture. See truck on I-90 near Vantage, WA, with 100 pound bales.
      http://s571.photobucket.com/user/norseman77/media/USA2011/DSC_4126.jpg.html

    • The affect of impoundments wouldn’t be corrected out of Rich’s numbers. (How could it be?) FWIW, the sea level folks do include an estimate in their sea level rise models — which are still a work in progress. IIRC, they think water held back in impoundments is currently roughly offset by water pumped from aquifers that finds its way to the sea. This is discussed in excruciating detail in IPCC AR5. chapter 13. Should you trust the IPCC sea level folks? I don’t know. My impression is that with exception of an arbitrary and probably inappropriate 15% upward adjustment in satellite estimates by the folks at CU their work is a lot closer to real science than the highly politicized and dubiously honest temperature estimates. But what do I know?

    • I wonder just how much fresh water is diverted to the oceans through sewerage treatment plants! I’ll bet its an astounding amount.

    • So what? All that water came from the oceans originally and goes back there. The only things that affects sea-level is water kept back permanently on land (in dams) or that was previously permanently on land but no longer (as in reclaimed lakes and wetlands and depleted aquifers).

      • I’d say the most significant land based storage of water is found in the underground aquifers. Recharge of aquifers likely dwarfs all the water kept in man-made lakes.

        Hence, I’d agree with the comment made above regarding water introduced to the system by pumps.

      • TTY

        You appear to be ignoring plate tectonics & collateral movements in the implied assumption that the shape of the oceans remains constant

    • Mark-Helsinki, Not sure this is what you mean or not but I remember (years ago) digging out data on river sediment for the major rivers around the globe and came up with an annual sediment volume estimate equivalent to about 0.01 – 0.05 mm/yr of ocean rise.

    • rigard — The problem is that just about every tidal gauge is moving upward or downward due to a variety of forces within the Earth. And, worse, we don’t know how fast they are moving at any given location. Eventually we’ll get high precision GPS measurements of vertical motion. But when you are trying to measure mm per year to a couple of significant digits relative to platforms whose position is known only to cm and you need to worry about other poorly known parameters like ionospheric delay, you need measurements taken over a long time period. How long. I don’t know. Decades probably. Anyway, you really can’t trust any single tidal gauge. It’s entirely possible that the blasted thing is moving up as fast as sea level is.

      • Certainly. Tidal gauges measure relative sea level. Which is after all the important one for a city.

      • I was waiting for someone to say that! Everyone seems to be focused on water when Geology has just as much, if not more, to do with these measurements. For example, the best explanation for the relative drop at Nagoya is that the land must be undergoing an uplift, probably due to a magma bubble or plume deep in the mantle. Similarly, southern Louisiana (although not mentioned here) is doomed to sinking further and further into the ocean because it is a sinking basin. And it should be noted that almost ALL river deltas around the world are located in sinking basins; that’s why the rivers flowed there in the first place.

        “Water is gravity’s dog, it follows it everywhere.”

      • tty: “Not really these days. GPS can measure altitude in geocentric coordinates with millimeter precision. But you need at least a few years measurement to get meaningful data.” More true than not. BUT. You really want good confidence to about a tenth of a mm I think. That’s about ten times the width of a human hair (depending on your choice of human). I think that’s likely to take a decade for any given site. Maybe two. And you probably can’t move the antenna or swap out the feedline or the receiver. Doable probably. But not easy. I hope to have less vague numbers some day.

  2. New Orleans is a delta city and we know what happens with deltas. I don’t see any reason why alarmists should even include delta cities in their claims.

    • “don’t see any reason” LOL. They always lead with the scare stories, facts be damned!!!

      This isn’t about science, this has never been about science, This is about building a politically persuasive case which would allow government to impose their will on whoever and whatever they wish.

  3. The city of Boston started out as the village of Shawmut. In 1630, the Puritans established their colony there. The history of Boston is considered to have started at that point.
    Since then, the city has suffered ~60 cm of sea level rise. As we all know, this has been utterly catastrophic to the original settlement. Indeed, absolutely nothing remains from those days.

  4. GPS elevation data for the past 15 or 20 years is also available on PSMSL for many of the tide gauge sites. This information can be used to help explain unusual tide gauge information. For example a GPS station at Quezon city some 8 miles inland from Manila shows a current very rapid rise of about 25 mm/yr starting with the station activation about 15 years ago whereas the tide gauge at Manila suggests the land there is rapidly falling at about 15 mm/yr since about 1960. Could Manila be tipping into the sea due to tectonic changes inland? Bangkok is also sinking while a nearby GPS station shows the elevation is pulsing up and down with a 1 yr period. Both of these cities show unusual tide gauge and GPS data which could be due to tectonic activity, not human activity.

    Tide gauge data must always be viewed in relationship to land elevation changes. If no elevation data is available, be cautious. For example, The Battery gauge at New York shows about a 3 mm/yr sea level rise as Mr. Taylor notes but about half of that is due to subsidence as shown by nearby GPS data.

    In “A Search for Scale in Sea-Level Studies,” Journal of Coastal Research, 2004, Larson et al. found that the rate of overall sea level rise determined from geologic data has been steady at 1 to 2 mm/yr for the past 6,000 years.

    It seems to me that if one looks carefully at tide gauge and elevation data, its hard to conclude that sea level is doing anything different from what it has been doing for a very very long time.

  5. CU haven’t updated their GMSL chart since mid July 2016, but at that time the global rate from 1993 was 3.4 ± 0.4 mm/yr.

    They also list the rates of the other producers who use similar methods, as follows:

    AVISO: 3.4 ± 0.6 mm/yr
    CSIRO: 3.3 ± 0.4 mm/yr
    NASA GSFC: 3.4 ± 0.4 mm/yr
    NOAA: 3.2 ± 0.4 mm/yr

    http://sealevel.colorado.edu/

    • So DWR54 if you adjusted for the pumped ground water addition to SLR and the adjustments made to increase their trend, then how much would that leave for actual SLR. Probably not much different than the tide gauge data.

      • It’s more a case of removing the adjustments tha CU make. Like GAIA adjustment for *assumed* ocean basin sinking and invserve barometer . I have no idea what diff IB makes to the global average because they refuse to provide data without it ! If it makes any difference to the global average there is a problem. If they hide it then it probably does.

        What you need to realise is that the water is all piling up in mid ocean where we can’t measure it ;) This is probably due to all the barometers !

    • I have never understood how global sea level to within a fraction of a millimeter can be determined from a satellite who’s position cannot be known to within a meter or so, using a radar beam of some 10’s of millimeters resolution on an undulating frothing surface of a liquid spanning 70% of the earth. There must be lots and lots of averaging going on, with very very large error bars, much larger than the +/- values given. And this producing data at odds with direct actual measurement of sea level with actual gauges and land level with very accurate GPS measurements. It doesn’t make sense to me, but then I am not an expert. Its been 25 years now with diverging numbers. Perhaps in another 25 or 100 years it will become clearer. But for now, it seems that the gauges are a better bet.

      • Actually the satellite position is (probably) known to a couple of cm. But there are plenty of possibilities for small error other than orbit uncertainties. The numbers you are looking at are the averaged results of the differences between “altitude” measured at the “same” position at different times. You’re correct. There is lots of averaging. HOWEVER, the great advantage of satellites is that there is no need to correct for tectonics — rise and fall of the ground under the measuring point. That’s a good thing because tectonic changes can be as large as or larger than sea level rise, and they are VERY difficult to measure.

      • It is less the position of the satellite that is the issue than the position of the bit of water which is reflecting the radar beam back up there. The strongest signal comes from the trough of the waves , not the mean position. It is all down to numerical modelling and the implied modellers’ assumptions. Basically you chose the result which best fits your assumptions of what it should be.

      • You’re right, although the beam width of the satellites is pretty broad compared to the wavelength of typical ocean waves, so the strongest signal will probably be some sort of compromise between closest and most area. But I suspect, don’t know for sure, that wave shape will also be a factor. I’m pretty sure that waves are only simple sinusoids when winds are light and that the apparent altitude might vary with wave shape — i.e. with wind strength and also current wind direction relative to the pitch of the swells. One more thing to average out?

      • Don’t forget that the shape of the wave will end up reflecting some of the energy so that it doesn’t return to the satellite.

      • DHR at 4:31 am. If my differential GPS can give me a location to ±2 cm, the position of the satellites must be known to better than that. And if I had needed millimetre accuracy, it was available at a higher price.

        So yes, the positions of all the satellites are known to within a millimetre. Precisely, at any instant. Even when they’re moving at 40,000 km/hr.

        If I had heard about this in high school in 1960, I’d have said “science fiction”.

        What’s really getting to the limits of my ability to comprehend is that an “instant in time” is not the same for me on the ground as it is for each satellite. It’s relativity in action, and the corrections are built into the software in the satellites. It’s just ………………………….. incredible.

        How is it possible for “us” to do stuff like that, and build spacecraft that can send us photos of neptune, and move around on Mars and send back chemical analysis of soil and rock, and “we” can’t build a laboratory where you could actually measure the radiant effects of CO2 in a precise replica of each layer of the atmosphere at different times of day, times of year, latitude, etc.? Could it be that those who dole out the research money don’t want to in case the results don’t meet their expectations?

      • “tectonic changes can be as large as or larger than sea level rise, and they are VERY difficult to measure”

        Not really these days. GPS can measure altitude in geocentric coordinates with millimeter precision. But you need at least a few years measurement to get meaningful data.

      • I asked the question a few months back as to why you can get latitude and longitude from your GPS device, but I’ve never seen one that gives altitude.
        I was told that the reason is because most GPS satellites are located in orbits that are near the equator.
        This gives good resolution in lat and lon, but poor resolution in the vertical.

      • “So yes, the positions of all the satellites are known to within a millimetre. Precisely, at any instant. Even when they’re moving at 40,000 km/hr.”

        Unfortunately not so. What Differential GPS for satellites measures is the change in distance between several simultaneously visible satellites and your receiver which is fine for trundling a combine around a wheat field. You don’t need to know the absolute distance to any of the satellites. You just need to know where you are relative to where you started..

        Even Trimble doesn’t claim to be able to measure position much better than a couple of meters with satellite based GPS. There’s also a ground station based Differential GPS system available in some places. It uses long-wave signals (285-325 KHz). Wikipedia says it can do 10cm location accuracy when the force is with you, but I doubt the vertical component — which is what we are interested in –is anywhere near that good. Unlike satellites, there wouldn’t seem to be a lot of vertical component information in such a system

        There are also augmentation services available in some places (WAAS in the US) that measure current GPS satellite errors and broadcast corrections.that receivers can apply. Wikipedia says measurements accurate to about a meter are possible. Which is great for a lot of purposes, but useless for measuring sea level rise.

        In principle you could use differential GPS to measure the rate of motion of a receiver tied to a tide gauge and the satellites. But to do that before the satellites set below the horizon you’d need to measure with micron accuracy.– which looks to be orders of magnitude beyond what can be done today.

        There’s a table of accuracies at https://en.wikipedia.org/wiki/Wide_Area_Augmentation_System#Comparison_of_accuracy

    • Colorado University’s Sea Level Research Group changes the data every time they release a new update. As a result, over time, the rate of sea level rise has substantially changed. The earliest time series of data that can be found on the Internet Archives WayBack Machine is from 2004.
      #version_2004_rel1.2
      The following graphic is a bit old (2014) but shows how the time series up to the 2004 mark had been changed. There’s not much Difference since then.

      Another way to look at it is to bring the overall rate of sea level rise forward one data point at a time and plot various releases against each other. The data starts in December of 1992 but has been plotted since 2000 because time series shorter than a few years are quite noisy.

      CU is overdue for a new release and will likely include Jason-3 data in the new release. It will be interesting to see what changes they apply to the historical data when that occurs.

      CU has published the title: Is the detection of accelerated sea level rise imminent? The link can be found at their website http://sealevel.colorado.edu/. It looks like they are “Telegraphing” what they intend to do.

      When it comes to science, we do live in interesting times.

      • Yet another demonstration that “climate science” has adopted the motto of the garment district: “If the man wants a blue suit, turn on the blue lights!”

  6. Sao Paulo sits at about 700 meters above sea level. The large population in this urban area is not at all threatened by sea level. The much smaller city of Santos is on the coast, but the land rises pretty rapidly from the coastline. This entire region is unlikely to be impacted much by sea level increases.

  7. Enterprising politicians from coastal areas would like their inland nieghbors to finance major infrastructure projects. AGW caused sea level rise provides a rational for making that request. Not very difficult to understand. The great beauty of the green beast is it’s ability to justify so much raw greed.

    • The solution to sea level rise is simple and inexpensive.
      As those buildings closest to the ocean reach the end of their useful lives. Instead of rebuilding in place, tear them down and rebuild a few miles further inland.

      • That is a fine solution, let the beaches go wild again. Beach re-nourishment projects in Florida are an expensive nightmare and result in beach sediments that more closely resemble paved parking lots than beaches. I’ve seen 2+M scarps on re-nourished beaches after a storm, making it necessary to dig chutes down to the water.

        PMK

      • Since the early 1970s Adelaide in South Australia that lies on Gulf St Vincent began sand carting from its northern beaches to replenish sand on its southern ones as they discovered with dying sea grass off the coast, there was a natural sand drift north. (Southern beaches were disappearing and coastal erosion was threatening property).That later included carting sand from inland sources like Mount Compass and now sand dredging and pumping it south as the costs of the King Canute trucking effort and rock walls and groynes rose.

        Had they decided from the beginning to let Mother Nature take its course and use the resources to buy back threatened buildings and esplanades, etc, to return the coast to natural absorbing and moving sand dunes, we may well have been in front. That would have meant slapping a non development order on all seaside property but you know how it is with those with sea views and instead we’ve had even more expensive high rise development and an escalating tail chasing dog.

    • It’s likely wore than that. After the Eemian interglacial ended about 115000 yrs ago, a very large amount of water was transferred from the oceans to the high latitudes of (mostly) the Northern Hemisphere. The Earth then (presumably) responded by shifting mass around internally to compensate. When the glaciation ended about 20000 years ago, the mass shifted back. But the change in mass isn’t just the removal of ice, it also includes flooding of continental shelves. And although the interior of the Earth behaves sort of like a viscous fluid, it doesn’t move around all that quickly. So i’s (almost certainly) still moving. And neither of the prevailing conceptual models of what happens to the surface at/near the edge of an ice sheet seems entirely satisfactory. The models of current vertical motion in areas affected by glaciation may well not be all that great. But they are all we have and are probably better than nothing, so they are what is used to estimate “glacial isostacy”

      • Don, maybe you could answer a question that has been lurking in my mind for some time. When large volumes of water are moved to high latitudes to become glacial ice, what is the effect on the rotational velocity of the planet?

      • Juan. I’m lousy at physics, but I think the same thing as what happens when a spinning ice skater pulls their arms in. The center of mass moves a bit closer to the axis of rotation. In order to conserve angular momentum, the skater/Earth rotates a bit faster. Anyone who actually understands physics should feel free to correct me.

      • What matters is the distance from the axis of rotation, not altitude per se.
        If low altitude water becomes high altitude ice, at the same latitude, then the earth’s speed of rotation will slow down.
        On the other hand glaciers tend to concentrate near the poles, which is quite a bit closer to the axis of rotation than the equator is.

        Assuming any loss of water will affect all oceans equally, you would then have to somehow integrate the average distance from the axis of all the world’s oceans. Doable, but I’m way to lazy to try.
        Then you would need to integrate the average distance from the axis for all the glaciers that are gaining ice.

        From that you can calculate whether mass is moving towards or away from the axis and how much.

        I strongly suspect that the earth spins faster when glaciers grow. However we are probably talking about shortening the day by just a few micro-seconds.

      • And this is the 900 pound gorilla in the room nobody talks about. If large amounts of ice in Greenland and Antarctica melts and in effect moves to lower latitudes the Earths’ rotation must slow down. Which the astronomers would immediately spot, but they can’t.

      • @ Juan Slayton
        @ tty
        There is a variation in the Length Of Day (LOD) of a couple of ms. on different cycles. One cycle is annual, about 2 ms. Another seems to be roughly 2 ms on a decade basis. All kinds of things are factors, from wind speed (conservation of angular momentum), water moving poleward in winter, tides with the moon, and Earth orbital parameters. (and probably a whole lot of other stuff)
        It is an ongoing, and fascinating area of study in Earth Science. It is a niche field, but underappreciated, I think.

      • “Assuming any loss of water will affect all oceans equally, you would then have to somehow integrate the average distance from the axis of all the world’s oceans. Doable, but I’m way to lazy to try.”

        Me to, but I think we can probably bypass the real math and just note that during a glaciation (with the current continental configuration) the water comes from everywhere and the new ice forms in high latitudes close to the axis of rotation. To preserve angular momentum — the rotation speeds up a tiny bit (not a lot–a few million cubic km of ice is an awesome amount, but pretty insignificant when compared to the total mass of the Earth) to compensate. Am I missing something?

      • The East Coast is a passive margin to boot. The further away from the spreading center, the cooler the slab.

  8. What I don’t see on the graphs is acceleration. The alarmists tell us that sea level rise is accelerating. They use high rates of sea level rise at some locations to goad us to do things about CO2.

    Here’s Judith Curry’s opinion.

    Sea level will continue to rise, no matter what we do about CO2 emissions. link

    • Only(nearly) global cooling will decelerate sea level rise. We should be glad there is none of that, yet, that we’ve perceived, though our lack of perception might be from the political need to perceive acceleration.
      ==============

    • Sea level data is extremely noisy due to a long list of things. IMHO anyone who claims to see an acceleration in sea level rise in the resulting plots is practicing fortune telling, not science.

      On the other hand, I agree with Curry. Much of the current modest rise in sea level seems to be due to thermal expansion of the oceans from 19th and 20th century warming (much of it probably natural) It’s apparently going to take a long time for that warming to work its way down to depth and for equilibrium to be established. So, I wouldn’t build anything that might be around centuries from now real close to sea level unless it’s something like a dock that HAS to be at sea level.

      And that’s ignoring inadequate allowance for storm surge in most current “planning”.

      Step back from the ocean folks, and no one gets hurt.

      • There is no time function in the relationship between volume change and temperature change. Any volume change is instantaneous with temperature change. The rate of volume change is a function of how quickly temperature changes. If the “old” heat is already in the ocean then the volume change has occurred. Any new expansion of the ocean depends on how quickly it’s temperature changes.

      • “There is no time function in the relationship between volume change and temperature change.”

        Not exactly. The issue is that the oceans aren’t “well mixed”, so it takes time — lots of it — for surface warming to work its way downwards. If you warm the surface by 1C now, whatever part that 1C that will eventually affect the temperature 300 or 3000 meters down won’t get there for quite a while. And it won’t all arrive at once either.

      • I don’t know but it seems to me that if the surface heats the deep of the ocean it has to be at cost of cooling the surface, provided there is no further external addition of heat. So, to reach the equilibrium, the deep warms and the surface cools. And if the surface cools it will shrink. George Costanza would agree.

        Anyway, I liked the article.

  9. An exellent survey of real sealevel rise. So the 3mm sea level rise used by climateers is because of US agency chauvinism (NY)and because it is, to them, like most climate change metrics, the maximum they can ‘decently’ get away with (add~100%). The official temperature anomaly trends are similarly jacked up by this bunch. And projections of T based on climate sensitivity that is triple reality.

    When sea level was flattening a number of years ago, they added on a crustal rebound correction (recovery from unloading ice since the glacial maximum), so now official sea level is up in the air above the sea a metric of no use. Smart climate scientists had better not rely on protest marching or prayer for future jobs, but rather sbould begin studies to correct all this Lysenko science.

      • Nantucket is made of glacial till. With any luck, wave action will erode away the beach front and the house will fall into the water. As a bonus, perhaps environmental protections will prevent the installation of any barriers to control the erosion. They are very fussy about messing around with things like that on the island. It would be such a shame.

      • @ MarkW
        It may be that Lurch no longer has the right connections since Hillary lost. They say that problem has been going around a lot lately.

    • I’ve already offered to buy the lower-campus parcel should they decide to move SIO uphill because of sea-level change. The shrewd real estate managers at Univ. of Calif., however, have always refused to consider my sincere offer.

  10. Thanks for the terrific post. I’ve lived at the same spot on the coast for six decades…”Sea level rise” is an anthem for which I don’t stand and salute.

    • I revisited a beach that I used to visit as a child over 50 years ago south of Adelaide. At low tide with the local reef just appearing it was quite clear nothing had changed. OK, not an accurate laser quality survey, but in 50 years the practical change amounts to nothing.

      • Guys
        what you are observing confirm my measurements.
        Namely, there has been no net warming in the SH over the past 40 years or so.
        All warming took place in the NH.
        Still, if you take a global average of the warming, it shows a natural curve: there is no man made global warming.
        Anyway, my expectation from my own results would be that sea level rise in the SH will be zero or close to that.

        Some of the results I glanced at here [e.g. in South America] and now your observations seem to confirm my suspicion….
        [unfortunately observation of sea level rise in the SH has been less carefully observed which is exactly the same problem I observed in all of the global T data sets ]

  11. It may be that the notion of a global sea-level-rise is even more meaningless than the notion of a global temperature-rise.

  12. One final comment. I think one should take the gross geology of the sites with a grain of salt. For example, the tidal gauge at Santa Monica is at the municipal pier. While Santa Monica itself is built on well consolidated albeit none too sturdy sediments (the cliffs slide onto the Pacific Coast Highway there with some regularity), the pier is built on a broad sand beach. My bet would be that the pilings do not go down to bedrock, but rather are just punched a few meters into sand. I wouldn’t be at all surprised that the pier is sinking a bit over time.

  13. All a mute point anyway. In 2008 President Obama declared publicly that his election signaled the era when the seas would stop rising. I haven’t followed up but I am certain that he would have kept that promise. Man I miss that guy and his biblical powers.

  14. There is no such thing as “sea level,” it is not at all level. The two ends of the Panama Canal have over a meter difference in “sea level.” Miami Beach is just one of hundreds of coastal cities built on dredged fill, although this is where Mr. Obama liked to show pictures of king tides flooding a city street. “There are three kinds of lies: lies, damned lies, and statistics…”

    • Michael, I have been trying to find sea level data on the two ends of the Panama Canal for literally 40 years. Do you have a reference for your statement? Pls share.

  15. Rich Taylor ==> Any analysis of Relative Sea Level Rise (local tide gauges) is incomplete without an examination of the local movement of the land itself relative to the center of the Earth. The issue is, of course, is the sea rising or is the land falling?

    The National Geodetic Survey (NGS), an office of NOAA’s National Ocean Service, manages a network of Continuously Operating Reference Stations (CORS) that provide some of this data.

    Locally, for local management, it matters very little. If Relative Sea Level is rising and encroaching on your waterfront park, who cares why. Either the land must be raised (or diked) or the sea lowered. Only one of those is possible.

    Miami Beach is built so close to [any] sea level that much of the city is already below known highest historical tide levels. New York City, which is moving towards the center of the Earth, has also restricted the sea’s access to its natural flood plain — the Meadowlands — which fact was partially responsible for the damage caused by Tropical Storm Sandy.

    Sea level is complicated. The seas are not a bathtub in which water rises evenly at all points.

    The seas are rising however, that is certain and they will continue to do so for the foreseeable future. This fact has almost nothing to do with anthropogenic climate change

    • There’s also the magma in the mantle sloshing around. The resulting high and low (by a few parts per million) gravity changes can result in water pilling up around areas with higher gravity.

    • MarkW beat me to it.
      However, I would like to add following: the Earth’s solid inner core diameter is about 20% of the total, it is not a perfect sphere but asymmetrical.
      Seismic tests suggests that there is an inner-core metallic crystallisation occurring in the western half while the opposite side melts, This is also confirmed by the secular changes in the magnetic field intensity, with the overall intensity of the magnetic field in the American continent is falling by 100nT/annum and rising by the similar amount in the Indian Ocean.
      In addition the core rotates at a somewhat different rate to the crust (0.3 degrees/annum , hmm…1000yr climate cycle comes to mind/sarc) causing a slight change in the gravity as measured at surface. Oceans surface will respond to these gravity changes however small. This, of course is all adding to the + or – gravity anomalies due to the isostatic postglacial uplift.

    • Wind also pushes the water around.
      We all know that the ENSO cycle changes the jet stream and the jet stream influences surface winds.
      So any long term change in the ENSO cycle would have an impact on tidal guages.

      • All this ‘sloshing around’, whether by wind or by movements in the earth’s mantle, would balance out over time would it not? I mean why would these random fluctuations influence the trend in only one direction over the past several decades?

      • ” I mean why would these random fluctuations influence the trend in only one direction over the past several decades?”
        No, the postglacial uplift started at least 10 to 15 thousand years ago, and it is still going on, the south coast of England is sinking while Scotland is rising.

      • “No, the postglacial uplift started at least 10 to 15 thousand years ago, and it is still going on, the south coast of England is sinking while Scotland is rising.”

        As I understand it glacial isostatic adjustment (GIA) is already accounted for by the satellite altimeter producers. The phenomena MarkW was referring to above are independent of this: sea level change caused by 1) surges in mantle magma and 2) winds.

        My questions concerned those 2 points rather than GIA. If these presumably fairly random factors have had a strong influence on GMSL rise over the past few decades then why has the trend been rising? Surely random factors like these would be expected to have a lowering effect around 60% of the time, balancing the system out.

      • Postglacial uplift doesn’t appear to be ‘smooth’ change. The epicentre of it is in the N-E Canada, It is assumed that 30% of secular changes in the magnetic field in the area are directly due to those changes and they show presence of significant ‘oscillations’. These are also visible in the The Hudson Bay “staircase” Periodicity varies between 40 and 70 years.
        Gravity changes caused by the asymmetry in the earth’s core differential rotation have periodicity estimated to be just over 1000 years.
        I’m not aware that either of two periodicities is accounted for in the tidal gauges data used for estimating global sea level data changes as presented by the AGW climate change advocates.

      • They do balance out over time. However time in this sense is thousands to 10’s of thousands of years.

      • MarkW

        A few posts back you were talking about magma in the mantle “sloshing around” and of winds pushing water around via energy from the jet stream. Now you’re referring to these processes as things that occur over “thousands to 10’s of thousands of years”.

        Even if the movement of magma in the earth’s mantle did cause ocean water to pile up around areas with higher gravity, that wouldn’t increase mean sea level, since water would just be drawn from elsewhere, lowering sea levels locally at those locations.

  16. The charts of sea level do not show any general acceleration, so one of the alarmist themes is unsupported. One thing though, terrane and terrain? I had been under the impression a terrane was a “foreign” i. e. formed in some other place chunk of landscape, not just a chunk of territory in general, as with terrain.

  17. Kip Hansen
    “Sea level is complicated. The seas are not a bathtub in which water rises evenly at all points.”

    I am surprised that the essay and reader comments don’t really talk about the planetary GEOID and how that affects mean sea level. If all of Greenland melted, theoretically the oceans would rise about 21 feet. But because of gravitational mass balance of that ice sheet, the melted water would tend to gravitate towards the equator and wind up on the opposite side of the planet from where the ice sheet had been. Was this essay only a geology lesson?

  18. The oceans are not in a fixed basin. I.e., mean sea level is NOT simply a function of how much water volume there is in the oceans. Until the size of the basin is known fairly precisely, any discussion of causes of sea level change is speculation.

    Changes could be 100% geological. We just don’t know. And, like Climate Science™, we don’t necessarily know what we don’t know.

    • Basin depth isn’t a problem for satellite altimeter data as it is calculated from the distance between the sea surface detected by the radar and the center of the Earth, giving a sea surface height (SSH), which is obviously independent of basin depth at any particular point.

      • DWR54 ==> Satellite measurements of sea level are approximations of averages of averages…..that means that the results are pretty iffy accuracy- and precision-wise. Read NOAAs pages on the Jason satellites and their hoped for accuracy, You will be surprised. The precision of claimed results is orders of magnitude smaller than their known margins of error. This results from a misplaced faith in the certainty and precision of averages.

        All that said, there is little doubt that the Earth’s seas are “still rising after all these years.” [h/t Paul Simon]

      • Kip Hansen

        “Satellite measurements of sea level are approximations of averages of averages…..that means that the results are pretty iffy accuracy- and precision-wise.”

        Well there appear to be at least 5 independent producers of such data and all of them are quoting an accuracy in the order of 3.2 to 3.4 ± 0.4 to 0.6 mm/yr, which is also pretty precise. What evidence is there that they’ve all got it wrong?

      • Irrelevant, DWR. Measuring sea level does not tell what has changed about the sea bottom. Plate movements, volcanoes, sedimentation, etc. You presume the basin is fixed.

  19. Does anyone do level surveys from solid benchmark triangulated base stations down to the tide gauges? This would seem a no-brainer thing to do given the angst over SL rise? Of course one can see the reason why climateers would rather not do anything to validate the tide gauges. It would also validate satellite measures. We may need to fund a project a la surfacestations. org.

  20. What a bunch of nuts. Next you’ll claim that the continents are drifting around. Settled science people. AGW is causing sea levels to rise at an alarming rate placing our most vulnerable citizens the elderly, sick, slow, mobility challenged, non-swimmers, small children, and generally lazy at risk. I propose a crash program of EV sustainably sourced and built motorised sofas for quick escape.

  21. There are about 70 PSMSL tide gauges with a differential GPS land motion correction within 10km. Of these, about 40 have long records. Those suggest a SLR of 2.1-2.2mm/yr and no acceleration according to SLR expert Nils Axel-Moerner. Moreover, that rate closes with an estimate of sea level rise based on the sum of ice sheet loss (Greenland, Antarctica based on GRACE) plus thermosteric rise based on ARGO. Once GRACE Antarctica is corrected for GIA using diff GPS rather than models (subject of a McIntyre post) the closrue sum is about 2.2-2.3mm/yr, remarkably good agreement considering the uncertainties. So any variation from ~2.1-2.2 is due to local conditions. For example Bangkok is subsiding rapidly due to groundwater extraction from unconsolidated river sediments.

  22. This is gravity anomaly map in from the Goce satellite data

    Highest positive anomaly is in two highly tectonic (volcanic) active areas:
    – far north Atlantic location of the great ocean conveyor belt pump
    – Solomon seas, with the strong elNino’s association
    both principal factors of the natural climate variability.

  23. Most interesting post. Thank you to Rich Taylor for assembling this data. I guess those reading it will take away from it what they will, according to their preconceived ideas. My take is that, all told, it is VERY unfrightening.

    For a greater perspective, I would be interested to see a table of the average trend at each port city set against the spring tidal range for the same places. This varies greatly according to location, with the lowest ranges in the Mediterranean, and some of the highest in the Atlantic. One can imagine that a rise of 2-3mm/yr would be unnoticed over centuries in much of the Atlantic but would, over time, be an issue for the Med (Venice anyone?)

  24. Here’s a nice six minute YouTube that pages through NOAA tide gauge charts showing how they match up against the 1.8 meters by 2100 projections from the the IPCC:

    • Sorry, I did not notice that you have already linked to this video; I only quickly viewed some comments and jumped to the end of the thread.

      It might also be worth pointing out the latest NASA finding on Antarctica. See: https://www.nasa.gov/feature/goddard/nasa-study-mass-gains-of-antarctic-ice-sheet-greater-than-losses

      A new NASA study says that an increase in Antarctic snow accumulation that began 10,000 years ago is currently adding enough ice to the continent to outweigh the increased losses from its thinning glaciers.

      The research challenges the conclusions of other studies, including the Intergovernmental Panel on Climate Change’s (IPCC) 2013 report, which says that Antarctica is overall losing land ice.

      According to the new analysis of satellite data, the Antarctic ice sheet showed a net gain of 112 billion tons of ice a year from 1992 to 2001. That net gain slowed to 82 billion tons of ice per year between 2003 and 2008.

      AND, the take home:

      The extra snowfall that began 10,000 years ago has been slowly accumulating on the ice sheet and compacting into solid ice over millennia, thickening the ice in East Antarctica and the interior of West Antarctica by an average of 0.7 inches (1.7 centimeters) per year. This small thickening, sustained over thousands of years and spread over the vast expanse of these sectors of Antarctica, corresponds to a very large gain of ice – enough to outweigh the losses from fast-flowing glaciers in other parts of the continent and reduce global sea level rise.

      Zwally’s team calculated that the mass gain from the thickening of East Antarctica remained steady from 1992 to 2008 at 200 billion tons per year, while the ice losses from the coastal regions of West Antarctica and the Antarctic Peninsula increased by 65 billion tons per year.

      “The good news is that Antarctica is not currently contributing to sea level rise, but is taking 0.23 millimeters per year away,” Zwally said. “But this is also bad news. If the 0.27 millimeters per year of sea level rise attributed to Antarctica in the IPCC report is not really coming from Antarctica, there must be some other contribution to sea level rise that is not accounted for.”

      (my emphasis)

  25. Rather than accept NOAA’s bogus post-glacial land adjustments, how about just looking at the sites least affected by glacial and tectonic uplift or down thrust? Africa and Australia come to mind. Maybe Atlantic South America, Dunno how much its east coast is affected by subduction in the west.

  26. Wow. A whole century of data. Now compare it to what? Good work but meaningless in the broad scheme of things. Also someone mentioned not rebuilding seaside homes. Excellent. Barrier reefs especially are here and gone in an historical blink of an eye.

  27. Meaningless bunk, produced by snowflakes and flat earthers in an attempt to shift wealth from producers to slackers and takers. Good luck with that, playing chicken little is amusing, until you want to take my money or your bogus science fantasy scenarios border on Orwellian wet dreams. Go cure cancer.

  28. The plethora of numbers, predictions, projections, and whatnot are just that. Someone, somewhere, will need to actually build something. Someone will need to make an engineering decision to roll up his sleeve and scoop some numbers out of the stinking quagmire of marginal statistics and use them to build something.

    That happened in 2000, for a project that needed to consider future sea level rise.
    The envelope, please.
    (Opens envelope with great drama)
    The winner is 0.9 ft by 2087.

    Documentation is here:
    Final EIR/EIS for the Bolsa Chica Lowlands Restoration Project
    https://searchworks.stanford.edu/view/4670333
    http://www.worldcat.org/title/final-eireis-for-the-bolsa-chica-lowlands-restoration-project/oclc/46913652

    Appendix B – Preliminary Engineering Studies Section B.3.1.4 Hydraulic Control
    “The National Council Marine Board (NMCB) has provided sea level rise predictions over the next hundred years as summarized in Table B-4. For the 100-year interval, 0.9 feet would be added to the tailwater elevation. . .”

    TABLE B-4 RECOMMENDED FUTURE SEA LEVEL
    RISE VERSUS TIME INTERVAL
    Interval (Years) Sea Level Rise (feet)
    5 –
    25 0.2
    50 0.5
    100 0.9
    Source: NMCB, 1987

  29. I think the key question is not whether the rise is 1.3mm/y or 1.5mm/yr – or similar – and what proportion of that is “man made” – but whether 1.3mm or 1.5mm has any significant consequences. If the answer is no or not much that can’t be managed, then the debate over the fractions of rise is a bit pointless. 1.3mm or 1.5mm or 2mm or year is not a very scary number…

  30. So let’s look at a very ancient and weathered continent that’s not moving very much nowadays and welcome to one of the longest recorded man made tide gauges in Gondwanaland-
    “One of the oldest tide gauge benchmarks in the world is at Port Arthur in south-east Tasmania. When combined with historical tide gauge data (found in the London and Australian archives) and recent sea level observations, it shows that relative sea level has risen by 13.5 cm from 1841 to 2000.”
    http://www.cmar.csiro.au/sealevel/sl_hist_few_hundred.html
    So that’s an average sea level rise of 0.85mm/year for over one and a half centuries.

    But in suburban Adelaide we have an even longer temporal tide gauge than that in the Hallet Cove Conservation Park, that none other than the current Premier Jay Weatherill recognised as a very important historical geological site when he proudly proclaimed it thus as Environment Minister in 2010. What does that tide gauge tell us all Premier? Let me remind a busy man trying to disprove the fundamental axiom of engineering that you can’t build a reliable system from unreliable componentry-
    http://sa.gsa.org.au/Brochures/HallettCoveBrochure.pdf

    “6. Shore platform
    The level shore platform has been eroded by wave
    action across the rocky coastline during the past
    7000 years. The big fold was formed during the
    mountain building about 500 million years ago.
    During the Recent ice age about 20 000 years ago,
    sea level was about 130 metres lower than today
    and South Australia’s coastline was about 150
    kilometres south of where Victor Harbor now is.
    The ice cap started to melt about 15 000 years ago.
    Sea level began to rise and reached its present level
    about 6000–7000 years ago”

    Now that could be an average annual sea level rise of 16.25mm/year over 8000 years. Can you now explain to us all Premier how the clever climatologists can extract the anthropogenic CO2 signal from the more recent sea level gauge in Tasmania compared to the one on our back doorstep? After all with Catastrophic Anthropogenic Global Warming, isn’t sea level rise the ultimate test of it whereby the sea rises because of thermal expansion or melting of snow and ice on land or the polar ice caps? Or was that 8000 year rise due to aboriginal cooking fires and traditional burnoffs to flush out game?

  31. For my bemusement. At the end of the last Ice age sea levels were about 375 feet lower than today. Than is 114,300 mm. Divided by 15,000 years – means since the last ice age ended sea level has been rising about 7.62 mm per year on average. Amazing how all of that coral survived

  32. the evs system in human is use in bad thinking

    On Wed, Mar 29, 2017 at 2:10 PM, Watts Up With That? wrote:

    > Guest Blogger posted: “Guest essay by Rich Taylor Abstract Human > population is becoming increasingly urban, and most of the world’s largest > and fastest-growing cities border tidewater. This note presents charts of > annual-value (AV) tide-gauge records in or near major coastal ” >

  33. A serious dose of sanity is required.

    The best insight into what is actually happening is to consider the actual data from tide gauges from around the world.

    There is nothing global about the changes in sea level, and this suggests that the expansion due to any warming of the oceans is not the dominant driver.

    It is well worth spending 5 minutes watching the below linked video.

    • richard verney March 30, 2017 at 3:16 am
      Sorry, I did not notice that you have already linked to this video …

      The real sorry state of affairs is that it has had less than 2,000 views and only 9 comments, and 3 of them are mine.

    • You statement “The trend for the last 100 years has been 1.5 mm/y, likely due to thermal expansion of sea water and the net transfer of water from continental aquifers to the ocean.” is falsified with above!

      • There are a few stations with long records. The 50 year average trend, shown above, is very important to study. Conclusion as above is easily falsified.

  34. Have us humans been factored in? each one of us 7 billion or so holds 50-100 liters of water that would otherwise go to the sea. I guess.

  35. The Maassluis gauge has the longest record; it sits about 15 km from the North Sea on the Maas channel that takes most of the flow through the Rhine (etc.) delta. Its 1.8-mm/y trend is also the average 100-year trend of the six long-standing gauges (Vlissingen, Maassluis, Hoek van Holland, Ijmuiden, Den Helder, Harlingen and Delfzijl) that monitor sea level for the Netherlands.

    Henry says

    I have no problem with these measurements, except for making/asking two points
    namely
    1) how have the instruments measuring this, changed over time? When, where, what changed.
    2) the measurement does not only indicate sea level rise but also a drop in the bottom of the ocean?Florida is a case in point.

    Another valid point I would make is that to present an actual global average [increase] you must present a sample that is balanced by latitude. Namely, my various data T analyses show an increasing chance that the warming in the NH is not balanced by warming in the SH. The ultimate conclusion from my data is that earth’s inner core must have moved a bit, more north-east, as noted by the movement of earth’s magnetic north pole.

    Let me know what you think.

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