Features Australia

Thank God for tide gauges

11 January 2020

9:00 AM

11 January 2020

9:00 AM

Between 1764 and 1767 William Hutchison, a mariner who was then Harbour Master at Liverpool in England, carefully recorded the times and heights of high tide at the Liverpool Old Dock. In the 19th Century the Mersey Docks and Harbour Board, that was to become the Liverpool Observatory, established state-of-the-art tidal stations along the nearby Mersey Estuary. In 1929 this Observatory merged with the Tidal Institute at the Liverpool University and this was to become a world-famous centre for sea level research. Today the Permanent Service for Mean Sea Level (PSMSL) maintains a database of tide gauge data from all over the world.

After the Intergovernmental Panel for Climate Change was formed in 1988 successive IPCC technical committees carefully examined the PSMSL tide gauge data as the computer climate models were predicting the acceleration of sea level rise. After all, a discovery of sea level acceleration would provide additional evidence of increased global warming due to rising carbon dioxide levels and proof of anthropogenic climate change.

Alas! Alas! There was almost a level of disappointment in the early IPCC reports. Despite all their efforts the committees in 1990 (13 experts), 1995 (24 experts) and 2001 (36 experts) stated that they could find no acceleration of sea level rise in the 20th century despite the rise of CO2 during that time. ‘There is no firm evidence of acceleration in sea level rise during this century’, said the IPCC Report of 1990 (Chapter 9, p.262).

All of this was to change in 2007 and the scientific mess left by that 2007 IPCC sea level committee is still with us today. The panel now numbered 70 scientists. The Head Coordinators were Dr Bindoff (University of Tasmania) and Dr Jurgen Willebrand (Leibnitz Institute of Marine Science).This was the first IPCC meeting when satellite-based sea level rise data were available. The first sea level satellite (Topex – Poseidon) was launched in 1992 and replaced by the Jason 1 satellite in 2001. The satellites were showing sea level rise around 30 cm per 100 years while the tide gauges examined at earlier IPCC meetings showed a much lower sea level rise of 15-18 cm per 100 years.


Without any detailed analysis of the discrepancy between tide gauge data and satellite data, this IPCC committee concluded the satellite data was more reliable. This was a false ‘eureka’ moment with a spurious conclusion that the higher readings of the satellite were proof that sea level rise throughout the 20th Century had suddenly changed from a steady rate of 15-18 cm/100 years to a rate of 30 cm/100 years in the 1990s. This interpretation was made without any detailed review of the reliability of tide gauge data from all over the Earth and technical altimetry problems in a satellite system; a system where a one millimetre of error in its 1,366 km orbital distance from the Earth’s surface translated to a sea level rise error of 10 cm in 100 years!

The sea level debate became an even larger can of worms in 2018. The University of Colorado, which manages the Jason satellites on contract to NASA, reported that not only had there been no acceleration of sea level rise in the satellite data there had been a deceleration in the last decade (2008-2018); so even the satellite data had not been able to detect acceleration of sea level! It was proposed that a cooling event due to the 1991 volcanic eruption of Mt Pinatubo in the Philippines had delayed the sea level acceleration that would have eventuated by 2018 but would still emerge from the noise of internal climate variability in the coming decade barring another major volcanic eruption.

This lack of sea level rise acceleration was consistent with a National Oceanic and Atmospheric Association report in 2016 on 200 tide gauges from the east and west coasts of the USA and from some Atlantic and Pacific islands. The US report showed there was no acceleration of sea level in these records. So two methods with vastly different results still showed no sea level acceleration! It was now crystal clear that the reports of no sea level acceleration (IPCC reports of 1900, 1995 and 2001) were correct and that the reports of sea level acceleration (IPCC reports of 2007 and 2014) were based on false logic; the spurious by-product of differences between two measuring systems.

The technical altimetry problems with the satellite system were eventually exposed in 2012 when NASA reported that there was a level of error that contaminated climatological data records, such as measurements of sea level height from altimetry missions. Consequently, NASA proposed to ditch the flawed Jason satellite system in favour of a new system called GRASP, or Geodetic Reference Antennae in Space. Unfortunately, its budget has never been approved.

So where are we today? The higher sea level rise estimates of the flawed satellite system are those most frequently quoted and fit with the many catastrophic climate scenarios. The United Nations’ climate Conference of the Parties in Madrid in December 2019, for example, quoted these higher sea level rise measurements and ignored the more reliable lower sea level rise estimates based on thousands of tide gauges. In Australia some scientists and engineers are still using the higher and dodgy satellite sea level rise data as a ‘prudential’ benchmark for coastal policies and have even adjusted tide gauge data upwards to the satellite data.

In 2014, for example, an engineering report for two NSW councils, Shoalhaven City and Eurobodalla, adjusted the Sydney Fort Denison tide gauge data, which showed a sea level rise less than 10 cm per 100 years, to the satellite measurements of 30 cm per 100 years. This absurd 300+ per cent upward adjustment of real tide gauge data was called a ‘linear fit’ (whatever that means!).

How can recent scientific articles published in ‘peer-reviewed’ literature stridently announce to the scientific community and the world media accelerated ice loss into the ocean from the Antarctic and Greenland ice sheets when there is no corresponding acceleration of sea level rise due to that ‘extra ice’. These articles tinged with panic do not make sense. The lack of any evidence of sea level acceleration in the PSMSL tide gauge data, the NOAA tide gauge data or even in the flawed NASA satellite data shows that these articles are either biased or based on insufficient data derived from flawed ice mass measurement methodologies. In contrast, the data from thousands of tide gauges clearly show no acceleration of sea level rise in the last 120 years.

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