NZCLIMATE TRUTH NEWSLETTER NO 319
by Vincent Gray, Wellington New Zealand
Chapter 13 of the IPCC 5th WGI Report claims that sea level will rise by an amount between 0.26 to 0.97 metres by 2100 according to which of their new scenarios actually happens
Relative Sea Level,the distance between the level of the sea and the level of neighbouring land is what matters to most of us. The Level of the open ocean is only of minor importance. This Report tries to mix the two up in a single chart.
Relative Sea Level is measured by tide gauges which measure the distance between the level of the sea registered on specialist equipment and a supposedly constant benchmark location on the neighbouring land. carried out in over 1000 coastal locations all over the world. The records are averages, over a day, week, month or years.
Both the level of the sea and of the neighbouring land constantly vary from place to place.and from time to time.
The sea changes level constantly, diurnally and seasonally. It is influenced by winds, storms and hurricanes and also by earthquakes. The level of the sea may be influenced by breakwaters and harbour works. The equipment may be damaged or its location altered by storms. Severe storms may prevent correct measurement and give a false reading which interferes with claims for “change.
Land surfaces may change. The land may subside by weight of buildings, and removal of minerals and groundwater. The Report illustrates the problem of measurement near land covered in iceGeological change (Isostasy) may result from plate movements and earthquakes. Many of these effects cause an upwards bias to the readings.
Long term trends may as much show these changes as any other influence. As a result they are not a reliable guide to the future.which should be based on a recent period of reliable measurements.
The recent installation of GPS levelling equipment on m,ay sites has greatly improved the reliability of the land-based benchmark. It has resulted in a nearly constant sea level change for many records it is therefore wrong to place reliance on older readings in order to assess future behaviour. It should be based on the most recent measurements which are the least likely to be affected by previous bias.
The records are publicly available at the Permanent Service for Mean Sea Level (PSMSL) website at at http://www.psmsl.org/data/obtaining/map.html which features a very convenient map of the world from which all the records can be obtained.
Many records are defective in one way or another. Many have gaps or sudden changes, Few have a long-term continuous record. Frequently there is little sign of change during the recent decade. evidence. that currently there is little or no change in sea level. The following figure from Chapter 13, FAQ 13.1 Figure 1. illustrates this error.
It shows six tide gauge records compared with the supposed global average..
The actual current records, which are shown (rather small), disagree with this supposed trend
San Francisco is unchanged since 1990.
Charlottetown is unchanged from 1995 to 2010.
Antofagasta is unchanged from 1980 to 2012
Pago Pago is unchanged since 2000.
Stockholm is actually falling.
Manila is a rogue record.The following website states that the gauge is subject to subsidence
The following records from the Philippines, show no recent rise.
I have published a study of the Pacific islands which also display no recent rise at
Recently there was a Pacific Forum meeting in Kiribati attended by our Prime Minister which complained that the islands were sinking. And we must take action
This is a recent tide gauge record from Kiribati
. These figures and also those from Australia continue to show little change. He same is true for many islands as shown at
Future projections for different places from the latest IPCC Report Chapter 13 are shown in their Figure 13.23 .
Every one of these actual measured sea levels have shown no sign of change for at least ten years, yet all the projections claim that this settled behaviour will suddenly change to an upwards level of around half a metre by the end of the century.
This is based on models which have failed to predict the lack of a global temperature increase for the past 17 year,.yet it is claimed they are causing melting of ice, particularly in the Arctic
All the models assume that any temperature rise will be least at the poles and greatest at the tropics because the water vapour feedback is lower at the poles..They do not mention Antarctica where the ice is currently increasing
There are no measurements of temperatures on ice anywhere, on ice caps, oceans or glaciers. In all cases there are other influences.on their behaviour. In the Arctic it is the temperature of the ocean and the behaviour of the ocean oscillations.
The ice in the Arctic is beginning to grow now
The satellite measurements do seem to show a steady increase in sea level, but it seems to be little known that the instruments are subject to drift and they have to be calibrated on tide gauge measurements,
This is described in the following web address
which can be boiled down to
These satellite measurements have only been going since 1992. There have been several calibration problems and it is unclear to what extent it incorporates errors from tide gauges
Models based on an assumption of a temperature change that is not currently happening, and on melting ice which is absent from Antarctica and which appears to have ceased in the Arctic, are poor guides to practical sea level changes near a coast. These need to be judged from tide gauges measuring recent local behaviour with reliable equipment,, . The IPCC “projections” are thereby grossly exaggerated.