Archives par mot-clé : Sea level

Le GIEC en est virtuellement certain…

by Prof. Dr. Jean N., 11 octobre 2019 in ScienceClimatEnergie


Le dernier rapport spécial du GIEC vient de sortir. Ce rapport, appelé SROCC (“Special Report on the Ocean and Cryosphere in a Changing Climate“), a été approuvé à la 51e session du GIEC tenue les 20 et 23 septembre 2019. Il a déjà fait beaucoup parler de lui dans les médias. Le résumé du rapport à l’intention des décideurs (SPM) a été présenté lors d’une conférence de presse le 25 septembre 2019. Pour ceux qui comprennent l’anglais, qui ont une formation scientifique et surtout qui ont le temps de lire 1170 pages, le fichier PDF de ce rapport est disponible sur le site du GIEC. Le présent article analyse le chapitre 4 de ce rapport, celui qui traite de la montée des océans. Rassurez-vous, nous n’allons pas critiquer la montée du niveau des océans qui est un phénomène bien réel. Nous allons plutôt montrer que les auteurs ont étrangement omis certaines explications qui relativisent la portée de leurs conclusions, notamment concernant la cause de la hausse du niveau marin.

1. Structure du chapitre 4

Ce chapitre 4 consiste en 168 pages et a pour titre “Élévation du niveau de la mer et conséquences pour les îles, les côtes et les communautés de faible altitude“. Les deux auteurs coordonnateurs de ce chapitre sont Michael Oppenheimer (USA) et Bruce Glavovic (Nouvelle Zélande). Les auteurs principaux sont au nombre de 13 et les auteurs contributeurs sont au nombre de 31. Au final, 46 scientifiques ont donc contribué à écrire ce chapitre. Rien que pour ce chapitre les auteurs citent un peu plus de 1500 références, essentiellement des articles scientifiques.

Qu’apprend-t-on dans le chapitre 4?

Pour faire simple, nous y apprenons : (1) Que le niveau moyen des océans monte toujours et que la vitesse s’accélère; (2) Que cette montée du niveau marin est essentiellement causée par l’homme; (3) Que l’on peut calculer ce qui va se passer dans le futur grâce aux modèles numériques; (4) Que l’on peut éventuellement se protéger de la hausse du niveau marin par toute une série de mesures.

Nous allons maintenant nous focaliser sur les points n°1 (montée du niveau) et n°2 (les causes).

2. La montée du niveau moyen des océans selon le SROCC

Nearly Half Of 53 Tidal Gauges Show Negative Sea-Level Rise

by K. Richard, Sep. 10, 2010 in ClimateChangeDispatch


The West Coast of North America has 20 long-term (90+ years) tide gauges measuring relative sea-level changes.

The East Coast has 33. Of the 53 total tide gauges, 45% (24) are negatively accelerating, 14 document falling sea levels, and just 11 have sea levels rising more than 3 mm/yr.

mage Source: Boretti, 2019

A cooling/non-warming North America

A few months ago, Gan et al. (2019) reported that the North American continent as a whole (180-0°, 15-60°N) “is one of the major cooling centers” in the Northern Hemisphere, with temperatures dropping after 1998 and no significant net change since the early 1980s apparent.

Historical European Sea Level Records

by Kip Hansen, Sep. 6, 2019 in WUWT


I have been working on another sea level related essay and in the process stumbled upon a paper published in 1990 by thePermanent Service for Mean Sea Level (PSMSL).  The title is: “On The Availability Of  European Mean Sea Level Data  by P.L. Woodworth, N.E. Spencer and G. Alcock  (1990)”,  The paper is listed on the PSMSL page of “Publications Relevant to the PSMSL and GLOSS” but is not available there.  [ a  .pdf is available here  courtesy of the library at the University of New Brunswick, Canada ].

La hausse du niveau de la mer accélère-t-elle l’érosion des côtes? (3/3)

by Prof. Y. Battiau, 30 août 2019 in ScienceClimat Energie


 

6. Conclusion

A la question initiale qui avait été posée – “la hausse du niveau de la mer accélère-t-elle l’érosion des côtes?”- on peut répondre qu’elle ne joue qu’un rôle mineur, comparé à celui des tempêtes. Dans l’état actuel des recherches, on peut dire aussi que le réchauffement climatique n’augmente pas la fréquence et l’intensité des tempêtes. Tout cela va à l’encontre de ce que l’on entend habituellement dans les médias, mais le scientifique a le devoir de rétablir la réalité des faits.

Pourtant, on ne peut nier que les risques littoraux s’aggravent dans beaucoup de régions et que leur gestion est de plus en plus coûteuse. Mais la plupart du temps, cette aggravation résulte de facteurs anthropiques. Alors que les hommes ont longtemps évité la proximité immédiate du littoral, ils ont depuis plus de 150 ans, entrepris d’installer habitations, infrastructures et complexes industriels le plus près possible de la côte. Face à cette vulnérabilité accrue, il a fallu ensuite “défendre contre la mer” tous ces biens, une stratégie qui n’a fait que renforcer ou déplacer l’érosion marine. La seule façon de prévenir efficacement les risques littoraux est de travailler avec les processus naturels et surtout de respecter la ressource sédimentaire du système côtier, en évitant d’entraver la mobilité naturelle du trait de côte. Mais ce serait là l’objet d’un autre article…

La hausse du niveau de la mer accélère-t-elle l’érosion des côtes? (1/3)

by Y. Battiau-Queney, 15 août 2019 in ScienceClimatEnergie


Il est courant de lire et d’entendre que la hausse du niveau de la mer, l’une des conséquences les plus manifestes du réchauffement climatique, va accélérer l’érosion de nos côtes, menacer de submersion marine de vastes zones littorales urbanisées et faire disparaître nombre d’îles basses habitées. Ces craintes sont-elles justifiées? Comme un consensus ne vaut pas vérité scientifique, on va essayer de démêler le vrai du faux en partant de l’état des connaissances scientifiques sur la hausse du niveau de la mer et analyser ses effets possibles sur les processus d’érosion des côtes.

 

1/ Que sait-on de la hausse du niveau de la mer ?

1.1. État des connaissances sur les variations passées et présentes du niveau de la mer à l’échelle mondiale

Une bonne synthèse récente sur les causes et l’ampleur de la hausse du niveau de la mer se trouve dans Cazenave et Le Cozannet (2014). On y trouvera une très abondante bibliographie antérieure à 2013. Les méthodes utilisées par les scientifiques pour évaluer la tendance moyenne de l’élévation du niveau de la mer dépendent de la période considérée. A l’échelle du Pléistocène (1 800 000 ans) et de l’Holocène (10 000 ans) on dispose d’archives sédimentologiques (repérage d’anciennes plages “soulevées”, analyse de niveaux tourbeux recouverts de sédiments marins, stratigraphie et datation de récifs coralliens …) et de données archéologiques, particulièrement riches sur les côtes méditerranéennes. On sait qu’à plusieurs reprises, pendant les phases interglaciaires du Pléistocène, le niveau de la mer a été supérieur à l’actuel de 5 à 10 m au moins (Planton et al., 2015). À partir du milieu du 19ème siècle, on utilise les données souvent précises des marégraphes installés principalement dans les ports de l’hémisphère nord. Elles fournissent les altitudes relatives du niveau de la mer par rapport aux terres émergées. Depuis 1993, les données satellitaires fournissent des altitudes absolues du niveau de la mer par rapport à l’ellipsoïde terrestre de référence et permettent d’avoir une vision beaucoup plus globale des variations du niveau des océans à toutes les latitudes et longitudes.

Tableau 1 : variations du niveau de la mer indiquées par les marégraphes (sources: SONEL et GLOSS; Wöppelmann et al., 2014 pour Marseille) (ND= non documenté). Les données dans les colonnes sont exprimées en mm/an.

Malfeasant Omissions? German Flagship ARD Broadcasting One-Sided, Drama-Making Sea Level Reporting

by Dr. S. Lüning, August 9, 2019 in NoTricksZone


What follows is another example of the tricks the mainstream media use to produce fake drama and urgency concerning sea level rise and climate change – namely omissions – and how geologist Sebastian Lüning held their feet to the fire.

Dr. Sebastian Lüning wrote a complaint to German ARD public broadcasting concerning its December 2, 2018, one-sided reporting of the Indian island of Ghoramara and the sea level rise it is allegedly experiencing. The €6.9 billion euro publicly funded, 22,612-employee ARD is the German equivalent to the UK’s BBC.

What follows is the exchange between Lüning and the ARD editorial staff:

With Sea-Level Rise, Climate Science Meets Reality

by J. Weatherall, August 6, 2019 in ClimateChangeDispatch


Numerous satellites utilized by Australian agencies and research bodies are able to take a measure of sea level by way of an altimeter. However, according to the CSIRO, it should not be overlooked that the signal to do so requires

# A satellite in an orbit which repeats the same ground track very closely (within about 1 kilometer)

# A radar system to measure the distance from the satellite to the sea surface to high accuracy. TOPEX/Poseidon and Jason-1 use two radar frequencies, Ku band (13.6GHz) and C band (5.3Ghz).

# A tracking system capable of locating the satellite vertically at any time to within a few centimeters. Some of the components of such a system are:

1/ Systems (usually a combination of GPS, satellite laser ranging and the French DORIS system) to locate the satellite

2/ A high-quality gravity model

3/ A model of the drag from solar wind and the atmosphere

4/ Suitable software to combine all of the above

Other corrections to correct the range:

On the satellite:

1/ A water vapor radiometer to measure the amount of water vapor between the satellite and the sea surface (the water vapor slows down the radar pulse, causing the raw measurement to be too long)

2/ Measurement of the range at two frequencies to estimate the “ionospheric correction” — that is, the degree to which the radar pulse is slowed down by free electrons in the ionosphere

3/ The troughs of waves contribute more to the radar reflection than the crests, so we need correction for this. This is estimated from the wind speed and the wave height, both of which can be estimated from the characteristics of the returned radar pulse.

On the ground:

1/ Ocean tide models to convert the raw altimeter measurement to “de-tided”

2/ Estimates (from a model) of the atmospheric pressure. This is used to calculate a correction to the radar range to compensate for the atmosphere slowing down the radar pulse

3/ A correction for the “inverse barometer” effect, where sea level is depressed in areas of high atmospheric pressure, and vice versa.

No one besmirches the accomplishments of the engineering and technology involved.

However, it is a basic truism that the greater the number of separate corrections needing to be applied, the greater the risk of miscalculation.

 

Study: Pacific Islands Will Survive Climate Change

by Eric Worrall, July 17, 2019 in WUWT


Who could have imagined that islands which survived rapid sea level rise at the end of the last ice age have no problem coping with changes in sea level?

Media Release
From: University of Auckland

Pacific atolls can adapt to rising seas and extreme storms – new study

Low-lying Pacific islands in atoll archipelagos such as Tuvalu, Tokelau and Kiribati are likely to adapt to the effects of climate change rather than simply sink beneath the waves, a new study shows.

Tuvalu, Tokelau and Kiribati are widely considered under threat from rising seas and severe storms due to climate change with their residents becoming ‘climate refugees’.

Researchers from the University of Auckland’s School of Environment recreated a scale model of tiny Fatato Island on the southeast rim of Funafuti Atoll in Tuvalu to test the ability of the real island to withstand predicted climate affects.

The study simulated higher sea levels and storm-generated waves up to 4m in a 20m-long water chute or ‘flume’ to replicate real-world sea levels of 0.5m and 1m in a purpose built laboratory at the University of Plymouth in the United Kingdom.

A beach at Funafuti atoll, Tuvalu, on a sunny day. Author Stefan Lins, source Wikimedia

The Holocene Sea Level Highstand

by David Middleton, June 6 , 2019 in WUWT


What is a highstand?

A highstand is one phase of the sea level cycle (AAPG Wiki)

  • Rising
  • Highstand
  • Falling
  • Lowstand

The highstand is the maximum sea level achieved during the cycle.

The Holocene Epoch

The Holocene Epoch was recently formally subdivided into three stages:

  1. Greenlandian Stage = Lower or Early-Holocene. 11.70 ka to 8.33 ka
  2. Northgrippian Stage = Middle or Mid-Holocene. 8.33 ka to 4.25 ka
  3. Meghalayan Stage = Upper or Late-Holocene. 4.25 ka to present

The abbreviation “ka” refers to thousands of years ago. Lower, Middle and Upper are generally used when referring to rock-time units. Early, Mid and Late are generally used when referring to time units (Haile, 1987). Prior to the formal subdivision, Lower/Early, Middle/Mid and Upper/Late were commonly used; however there was no formal nomenclature. The fake word, “Anthropocene” is not used by real geologists.

There is also an informal climatological subdivision of the Holocene:

  • Preboreal 10 ka–9
  • Boreal 9 ka–8 ka
  • Atlantic 8 ka–5 ka
  • Subboreal 5 ka–2.5 ka
  • Subatlantic 2.5 ka–present

Source: Wikipedia

Why would there have been a Mid- to Late-Holocene highstand?

Figure 1. Holocene sea level curves from Moore & Curray, 1974.

Another climate lie bites the dust – No, Honolulu’s beaches aren’t going to disappear in 20 years

by Aylin Woodward, April 25, 201 in WUWT


In May 2017, high tides engulfed parts of the iconic Waikiki beach, edging dangerously close to waterfront hotels. This kind of high-tide flooding, often called a king tide or sunny-day flood, occurs when ocean water surges to higher levels than coastal infrastructure was designed to accommodate. In that case, water levels rose 2.5 feet above average in Waikiki, drowning nearby roads and sidewalks.

According to a 2017 report (which was updated in September 2018), Hawaii’s state capital and Waikiki Beach – along with other coastal strips on Hawaii’s five islands – are expected to experience frequent flooding within 15 to 20 years.

“This flooding will threaten $5 billion of taxable real estate; flood nearly 30 miles of roadway; and impact pedestrians, commercial and recreation activities, tourism, transportation, and infrastructure,” Shellie Habel, lead author of the 2017 study, said in a release.

Now, Hawaii state lawmakers are taking steps to shore up the state’s beaches and coastal cities. A new bill that mandates a statewide shore protection program has passed both houses of Hawaii’s state legislature, and will soon makes its way to the governor’s desk for approval.


All well and good that they want to improve beach resilience. But, the claim that ” Hawaii’s iconic Waikiki Beach could be engulfed by the ocean in 20 years ” is totally bogus.

Here is why:

 

Isle de Jean Charles & Sea Level Rise

by P. Homewood, April 20, 2019 in NotaLotOfPeopleKKnowThat


The Isle de Jean Charles, Louisiana. It’s been largely submerged beneath the sea over the last 6 decades. The program gives the definite impression that the main reason for this inundation is sea level rise due to melting ice and thermal expansion of the oceans – driven by man-made climate change. Attenborough does mention oil extraction as a cause but his narrative is lost to the general tone of the messaging that this is a “climate catastrophe” and that the families driven from their homes in this part of Louisiana are some of the world’s first “climate refugees”. This is palpable bullshit.

 

https://tidesandcurrents.noaa.gov/sltrends/sltrends.html

CA sea level rise alarmist study ignores 30 years of NOAA data with no coastal sea level rise acceleration

by Larry Hamlin, March 13, 2019 in WUWT


NOAA tide gauge data measurements exist for 17 locations along the California coast with 8 of these locations having actual measured sea level rise data covering periods for more than 70 to 120 years in duration.

This measured data shows that none of these California locations are experiencing coastal sea level rise acceleration since climate alarmist first made such erroneous and flawed sea level acceleration claims before the U.S. Senate in 1988.

Climate alarmists and their supporting media conveniently conceal the fact that their flawed claims have been hyped for the last 30 years as they continue to try again and again to make the same repeated but flawed claims apparently hoping that the public will forget their long track record of failure and exaggeration.

NOAA measured tide gauge data shows that coastal sea level rise at Ca. locations varies between 3 to 12 inches per century and have remained at those levels during the long measurement periods during which actual measured data have been recorded with a sample of that measured data shown below for San Diego, La Jolla, Los Angeles and San Francisco.

New Paper: Widespread Collapse Of Ice Sheets ~5000 Years Ago Added 3-4 Meters To Rising Seas

by K. Richard, March 11, 2019 in NoTricksZone


During the Mid-Holocene, when CO2 concentrations were stable and low (270 ppm), Antarctica’s massive Ross Ice Shelf naturally collapsed, adding the meltwater equivalent of 3-4 meters to sea levels.

Because CO2 concentrations changed very modestly during the pre-industrial Holocene (approximately ~25 ppm in 10,000 years), climate models that are predicated on the assumption that CO2 concentration changes drive ocean temperatures, ice sheet melt, and sea level rise necessarily simulate a very stable Holocene climate.

In contrast, changes in ocean temperatures, ice sheet melt, and sea level rise rates were far more abrupt and variable during the Holocene than during the last 100 years.

Modern ocean changes are barely detectable in the context of natural variability

Image Source(s): Rosenthal et al., 2013Climate Audit

What’s Natural? Changing Sea Levels – Part 1

by Jim Steele, February 23, 2019 in WUWT


Local sea levels appear to rise when ocean volumes increase, but also when the land sinks. Scientists increasingly warn that coastal cities are sinking much faster than ocean volumes are rising. Pumping out groundwater not only causes lands to sink, it increases the oceans’ volume. China’s Huanghe Delta is sinking 10 inches a year. Southeast Asian cities battle sinking rates of 1.2 to 2.4 inches per year. Regions around Houston, Texas had sunk 10 feet by 1979; a disaster waiting to happen where hurricanes commonly generate 15-foot storm surges. Likewise, New Orleans was doomed by sinking 1.4 inches per year. Built on marshland, San Francisco’s airport sinks 0.4 inches per year.
In contrast, ocean warming plus added glacial meltwater are estimated to have only added 0.06 inches per year to sea level from 1850 to 1990, punctuated by decades that accelerated sea level rise to 0.14 inches a year. Still, that fastest rate of modern sea level rise remains only one-tenth of New Orleans’ sinking rate.

A global assessment of atoll island planform changes over the past decades

by E. Duvat, October 25, 2018 in WiresClimateChange


Over the past decades, atoll islands exhibited no widespread sign of physical destabilization in the face of sea‐level rise. A reanalysis of available data, which cover 30 Pacific and Indian Ocean atolls including 709 islands, reveals that no atoll lost land area and that 88.6% of islands were either stable or increased in area, while only 11.4% contracted. Atoll islands affected by rapid sea‐level rise did not show a distinct behavior compared to islands on other atolls. Island behavior correlated with island size, and no island larger than 10 ha decreased in size.