Hvorfor er månecyklen på 18.61 år relevant i klimasammenhæng ?

Now that altimetry has provided two decades of high-quality data, people have started to investigate whether possible nodal signals in that data set have an equilibrium response. Cherniawsky et al. (2010) searched for nodal signals in altimeter spatial fields but concluded that the obtained "amplitudes and phase values likely arise from this [ocean] variability and not the nodal tide."

The 18.6-year nodal tide is a component of all tide gauge records. It can affect estimates of sea level acceleration, in particular for tide gauge records with lengths of less than 60 years. We provide an analytic solution that shows the effect of the nodal tide on estimates of sea level trend and acceleration. By adding a term to the least squares formulation used to estimate sea level trend and acceleration, we can account for the nodal tide and eliminate its effect on the estimate. Using representative world-wide tide gauge records, we demonstrate that accounting for the nodal tide can improve estimates, particularly of acceleration.

Periods of high astronomically generated tides contribute to the occurrence of extreme sea levels. Over interannual time scales, two precessions associated with the orbit of the Moon cause systematic variation of high tides. A global assessment of when these tidal modulations occur allows for the prediction of periods when the enhanced risk of coastal flooding is likely in different parts of the world. This paper uses modeled tides to assess the influence of the 18.61 year lunar nodal cycle and the 8.85 year cycle of lunar perigee (which affects high tidal levels as a quasi 4.4 year cycle) on high tidal levels on a global scale. Tidal constituents from the TPXO7.2 global tidal model are used, with satellite modulation corrections based on equilibrium tide expectations, to predict multidecadal hourly time series of tides on a one-quarter degree global grid. These time series are used to determine the amplitude and phase of tidal modulations using harmonic analysis fitted to 18.61, 9.305, 8.85, and 4.425 year sinusoidal signals. The spatial variations in the range and phase of the tidal modulations are related to the global distribution of the main tidal constituents and tidal characteristics (diurnal or semidiurnal and tidal range). Results indicate that the 18.61 year nodal cycle has the greatest influence in diurnal regions with tidal ranges of >4 m and that the 4.4 year cycle is largest in semidiurnal regions where the tidal range is >6 m. The phase of the interannual tidal modulations is shown to relate to the form of the tide.

The observed amplitudes of the 18.6-year nodal constituent MnMn are relatively small, 1.5–3.5 cm. These values significantly exceed its theoretical amplitudes, which are less than 1 cm almost everywhere. The analysed signals at MnMn frequency are therefore of mostly non-tidal origin, part of the broad-band decadal ocean variability.

Sea-level rise rates have become important drivers for policy makers dealing with the long-term protection of coastal populations. Scenario studies suggest that an acceleration in sea-level rise is imminent. The anticipated acceleration is hard to detect because of spatial and temporal variability, which consequently, have become important research topics. A known decadal-scale variation is the 18.6-year nodal cycle. Here, we show how failing to account for the nodal cycle resulted in an overestimation of Dutch sea-level rise. The nodal cycle is present across the globe with a varying phase and a median amplitude of 2.2 cm. Accounting for the nodal cycle increases the probability of detecting acceleration in the rate of sea-level rise. In an analysis of the Dutch coast, however, still no significant acceleration was found. The nodal cycle causes sea level to drop or to rise at an increased rate; therefore, accounting for it is crucial to accurately estimate regional sea-level rise.

This work shows statistical evidence for lunar nodal cycle influence on the low-frequency summer rainfall variability over the plains to the east of subtropical Andes, in South America, through long-term sea surface temperature (SST) variations induced by the nodal amplitude of diurnal tides over southwestern South Atlantic (SWSA). In years of strong (weak) diurnal tides, tide-induced diapycnal mixing makes SST cooler (warmer) together with low (high) air pressures in the surroundings of the Malvinas/Falklands Islands in the SWSA, possibly through mean tropospheric baroclinicity variations. As the low-level tropospheric circulation anomalies directly affect the interannual summer rainfall variability, such an influence can be extended to the bi-decadal variability present in the summer rainfall owing to the nodal modulation effect observed in the tropospheric circulation. The identification of the nodal periodicity in the summer rainfall variability is statistically robust.

Analysis of 38 tree ring chronologies yields evidence for enhanced drought conditions every 18.6 years in the North American interior for the past millennium. Cross spectra between a drought area index and 26 temperature records confirm the analysis of Currie (1979, 1981d) as regards a lunar nodal MN term in these data. Discussion of the MN tidal constituent, which appreciably modulates amplitude and phase of four main constituents (M2, K1, O1, Mf) is presented, and implications for agriculture are surveyed.

A possible connection between oceanic tides and climate variability arises from modulations in tidally induced vertical mixing. The idea is reexamined here with emphasis on near-decadal time scales. Occasional extreme tides caused by unusually favorable alignments of the moon and sun are unlikely to influence decadal climate, since these tides are of short duration and, in fact, are barely larger than the typical spring tide near lunar perigee. The argument by Keeling and Whorf in favor of extreme tides is further handicapped by an insufficiently precise catalog of extreme tides. A more plausible connection between tides and near-decadal climate is through "harmonic beating" of nearby tidal spectral lines. The 18.6-yr modulation of diurnal tides is the most likely to be detectable. Possible evidence for this is reviewed. Some of the most promising candidates rely on temperature data in the vicinity of the North Pacific Ocean where diurnal tides are large, but definitive detection is hindered by the shortness of the time series. Paleoclimate temperature data deduced from tree rings are suggestive, but one of the best examples shows a phase reversal, which is evidence against a tidal connection.

Det er ganske løjerligt, at det har voldt så mange følelsesmæssige udbrud fra svorne klimabenægtere her på klimadebat, at jeg har undersøge de omtalte cykler både globalt og lokalt.

kfl hævder imod al fornuft, at der er månecykler i data for gennemsnitlig global vandstand. Han finder de lavfrekvente månecykler 8.85 og 18.61 år i en 20 års dataserie, siger han! Wauw!

Han forklarer ikke, hvordan det skulle kunne gå for sig. Det er baseret på rene statistiske curvefits.

Hvornår skulle denne magiske effekt teoretisk set være størst og mindst? Passer det med det, kfl finder? Vi ved det ikke. Hvordan kan det være, at effekten i kfl's analyser har maksimum på samme tid, altså at tidevandseffekten skulle give højvande på den sydlige og nordlige halvkugle på samme tid? Det giver ingen mening. Skulle vandet på magisk vis forsvinde ud til polerne, hvor satellitterne ikke kan se det, eller?

respekt for folk som inddrager usikkerhed i betragtningerne. Det er der mange som kunne lære og usikkerhed bør være obligatorisk i al kvantitativ analyse. Det er det desværre ikke.

Enig, men det hjælper ikke at være opmærksom på statistisk usikkerhed, hvis man analyserer sine data med hovedet under armen og for eksempel postulerer en effekt af tidevandscykler på 8.85 og 18.61 år i en 20 års dataserie uden skygge af teoretisk belæg. Og fremturer med det samme igen og igen.

Men kfl, hvornår skulle effekten give højvande hhv lavvande på globale data fra CU og hvorfor? Det er jo som bekendt ikke en virkelig effekt (som er nul) men en målefejl, du postulerer.

The GMSL rate corrected for GIA represents changes in water mass and density in the oceans. These changes are thought to be predominantly driven by thermal expansion of the oceans and land ice melt (Greenland and Antarctic ice sheets and glaciers).

sg17a skrev:
N A Nielsen, hvorfor forholder du dig ikke til indholdet i stedet for at komme med disse personlige angreb?

Selvom det forventes, at der kun er en ringe eller ingen indflydelse fra månecykler på den globale vandstand, er det naturligvis af interesse at undersøge om det forholder sig således. Det er det jeg forsøgt og Cherniawsky forsøgt.

Med udgangspunkt i data for den globale vandstand fra Colerado Univesity, har undersøgt om 18.61 og 8.85 cyklerne kan spores i den globale vandstand. Jeg har fundet amplituderne fra disse ca. 2 mm og ca. 1 mm henholdsvis – ret til ændringer forbeholdes. Det er selvfølgelig muligt, at disse værdier stammer fra andre kilder end månecyklerne, men de er der.

Der er flere relevante reference i følgende link:

Kblog:The lunar nodal cycle and its effects on climate

UN climate conference in Lima collapses and defers all contentious issues to next meeting


The UN climate conferences are an exercise in futility for something quite unnecessary. But they provide an annual jamboree for the "global warming community" of do-gooders, pseudo-scientists, advocacy groups, bureaucrats and politicians. They have been meeting for over 2 decades and have achieved nothing. The ostensible goal is to get the world to reduce carbon dioxide emissions so as to limit global temperature rise. But during the life of these nonsensical meetings, the world's emissions of carbon dioxide has increased by over 70%. Carbon dioxide concentration in the atmosphere has risen by about 15% and it is uncertain how much of that is due to man-made emissions. But while all this has been going on, global temperature has remained stagnant and may even have decreased slightly.

So one wonders why the UN keeps hosting these incredibly wasteful and pointless meetings. But of course this is because the meetings are not really pointless – they have a hidden agenda. And this agenda is all about the getting of funds and the redistribution of money. And that automatically divides the participant countries into those who will pay and those who will get. The largely parasitic "global warming community" is always on the receiving end and has a vested interest in keeping these meetings and their funding alive indefinitely. Never mind that nothing significant is achieved as long as their funding continues.

The conference in Lima has been no different. It has all been about rich countries putting money (which countries and how much?) into a pot which other so-called developing countries can dip into (who, when and how much?). It is inevitable that the fringe elements supporting the redistribution of wealth, from the creators of wealth to the consumers of wealth (and these fringes are always consumers), are well represented at these conferences. Listening to some lobby groups it sounded like "a conference for the promotion of socialist ideals". Greenpeace made an utter fool of itself again by their cheap publicity stunt causing damage, pollution and desecration of the Nazca Lines site. John Kerry showed up for a day and made his alarmist speech. Al Gore made a speech on the sidelines noticeable for the number of empty seats.

kfl skrev:
Forklaringen på at cyklerne på 18.62 og 8.85 år kan identificeres i den globale vandstand målt ved satellitter kan være

1.Polar gap, dvs. satellitdækningen kun +/-66 breddegrader svarende til 90%'s dækning. Kan højst forklare 2 mm i amplituden
2.Modulation af de harmoniske konstanter
3.Ikke-lineære tidvandseffekter, f.eks. amphidromer
4.Der foreligger kun ca. 22 år med satellitmålinger
5.Variationer af PDO, ENSO

Jeg har ikke viden nok til afgøre, hvad der er den korrekte forklaring.

Det er for alle andre end tidvandseksperter vanskeligt, at finder ud af hvilke korrektioner man foretager i satellitmålingerne. Nogle af disse korrektioner ligger dybt begravet de mange underliggende IT-programmer både principielle ting og numeriske tilnærmelser.

Fra egen erfaring ved jeg, at der i store IT-systemer kan ligger fejl af forskellig slags, som man først opdager mange år senere. I en så kompliceret verden som måling af den globale vandstand, vil man derfor løbende se, at man opdager fejl og som man korrigere for. Derfor er det ikke udelukket, at der kan ske ændringer i data således, at de cyklerne på et tidspunkt vil forsvinde fra de globale data. Tiden vil vise det....

kfl skrev:
Der er belæg for at undersøge om de påståede cycler findes i den globale vandstand og om de fører til fejlagtigt tolkninger af udviklingen i den global vandstand. Det er det jeg og andre har gjort.

Det er ligeledes at afstemningsspørgsmål, idet disse cykeler i flere lokale havområder. Det vil være naturligt, at se om disse cycler findes når alt lægges sammen. Det er det jeg og andre har gjort.

Det er det jeg forsøgt og Cherniawsky forsøgt.

For regional sea-level rise estimates, the spatial variability of the nodal cycle is relevant. This spatial variability is also relevant for estimating the global mean sea level. The global mean sea level itself is not affected by this cycle, but trend estimates can be affected because both tide gauges and the satellites have limited coverage of the world. Tide gauges have higher coverage in the Northern Hemisphere, and the altimetry satellites only cover the area between −64° and 64°.

The sea-level trends based on tide gauges can also be affected by the nodal cycle because of irregular spatial sampling of the tidal gauges. The observed nodal cycle shows a pattern that is more E–W [east-west, NAN], rather than the equator–poles pattern of the equilibrium. The nodal cycle [18,6 års månecyklus] can thus be safely ignored for global mean sea-level estimates based on satellites