The deception of rising sea levels
One of the more mystifying claims in the global warming/climate change debate is that of sea levels rising. There is a huge variation amongst scientists, from Al Gore's figure of 65m per century to NIWA's 1998 Lyttelton study of 1mm per year (10c per century); a disparity of 65,000%. That degree of error disqualifies claims of plausibility, even throwing doubt on NIWA's work.
With that degree of uncertainty, it is difficult to see how anybody can be sure the sea is rising at all.
How, it may be asked, can 1mm change in sea level be calculated, averaged over one entire year or a hundred years, when even a flat sea at rest undulates more than that with waves every few seconds, and tide height just in one day varies by some two metres.
To say a tide height is higher we require knowing higher than what? To fairly compare tide heights one needs a past reference height to compare with one in the present.
Finding the former is not possible because (at least 10) factors that influence tide height do not together repeat.
We are talking of phase of the moon, lunar declination, perigee cycle, high and low pressure zones that can suck heights up or depress them, and winds onshore that can blow water into a harbour or offshore depleting a bay.
Equinox tides are higher than solstice tides. The sea is warmer in summer, therefore higher. Underwater earthquakes, eruptions, and fissures raise local sea-levels, most non-recordable and/or undetectable.
Rainfall at sea, river flows and land run-offs contribute to sea-levels. Temperature changes control density and water volumes, ever-shifting in the ocean, and the direction of currents both deep, mid and surface, alter sea height. Cycles of glaciers' advance and retreat change heights of the ocean.
In short, we haven't a clue how high sea levels are ever supposed to be in any fixed place, to a tolerance of 1mm per year, when everything connected to the sea is in constant flux.
The sea is not a lake or a pond. No computer model can pretend that it is, just for the sake of a neat result.
Examinating old photographs, sketches and tide markers reveals high watermarks unchanged on NZ beaches, apart from erosion due to changing currents.
Disappearing sand is a cycle, a function of lower than normal sea levels because lower water undermines foreshore and top sand collapses.
Without higher water to re-deposit sand higher up the shoreline, over a long time period a beach can ebb slowly away.
Higher tides deposit more sand because sand is heavier than water - surf brings sand in by momentum of wave action, and leaves it there when water recedes. Erosion cycles are just that, cycles.
As of last month we have started getting higher than normal tides again, after months of smaller tidal variation. Erosion on east coast beaches like Ngunguru, Whitianga and Hawkes Bay will reverse as sand is replaced.
If this was not cyclic, all sand on all beaches would have gone long before now.
Without monitoring over all oceans we cannot know if sea-levels are rising.
We only have measuring devices on 0.4% on the earth's surface where humans live. Special buoys now report via satellite using Argos transmitters, but we need to wait several centuries to achieve a reliable average to comment on any future century's departure from average.
Antarctic and Arctic ice are thickening, which means sea levels are dropping.
On Tuvalu and other island atolls it is the land that is moving, not the sea. Small atolls like Tuvalu cannot be sliding under the sea whilst beaches in Australia and NZ stay unaffected. How would the sea decide which countries to send beneath the waves?
As we emerge from this interglacial the poles are the smallest they have been in a while and some sea-levels the highest they aspire to. Some countries are still rebounding after the last ice age- Scotland is rising and the south of England is lowering. The west of Australia is rising whilst the east is dropping. There is a similar differential between our north and south island.
The high watermark on any beach varies up and down the sand by about a metre every 10 minutes. To that add just 1 millimetre per year, the thickness of a grain of sand.
Is the thought of that terrifying anyone?
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