Monthly Archives: October 2021

Trends in sea level at Cooktown, Great Barrier Reef

Mean sea level change at Cooktown, Great Barrier Reef, Queensland

Dr Bill Johnston


Main points

  • There is no evidence that melting glaciers, increasing levels of atmospheric CO2­­ or expansion of the oceans due to rising temperatures has caused sea levels to increase at Cooktown. Consequently, the likelihood that sea level will rise by 26 to 29 cm by 2030 as suggested by the IPCC is far-fetched.
  • As trends measured by multiple tide gauges adjacent to the reef differ from satellite-based estimates, and time-lapse aerial photographs since the 1950s show no shoreward encroachment of tidal wetting fronts, satellite data should not be used in critical studies or to inform government policy.
  • The El Niño Southern Oscillation exerts an overarching impact on fluctuations in sea level and other climate and environmental variables.


The Great Barrier Reef Marine Park Authority (GBRMPA) claims that due to global warming, sea level is increasing and that the fastest rate of sea level rise is in the northern sector of the Reef. Further, the Intergovernmental Panel on Climate Change (IPCC) predicts sea level will rise by around 26 to 29 centimetres over the next 9-years (i.e., by 2030) and by 47 to 62 centimetres by 2080.

But is it true or is it just untrustworthy science?

Rapid rates of sea level change should be evident in mean sea level (MSL) measured by tide gauges relative to the land, especially at Cooktown where Maritime Safety Queensland has operated an automatic tide gauge since January 1996 (Figure 1). Also, evidence of shoreline encroachment resulting from sea level rise should be obvious in time-series of aerial photographs available from Queensland Government archives since the 1950s and 1960s. 

Figure 1. The Cooktown storm surge tide gauge (arrowed) located on the wooden-decked wharf prior to its restoration in 2015. (Photo 44740 from the Cultural Atlas of Australia.)  

What we did

High-frequency (10-minute) tide gauge data was downloaded from the Queensland Government Open Data portal, aggregated into monthly averages and analysed using a technique that partitioned variation IN the data caused by influential covariables, from underlying impact variables that impacted ON the data-stream.  

Aerial photographs taken in 1969, 1974, 1979, 1983, 1987, 1989, 1991, 1994 and high-definition Google Earth Pro Satellite imagery were also examined for signs of tidal encroachment at Cherry Tree Bay east of Cooktown across the peninsula.

What we found

The Bureau of Meteorology Southern Oscillation Index (SOI) was the most influential of a range of climate and environmental variables that affected MSL. Rainfall and rainfall two months previously (RainLag2) also explained a statistically significant but small portion of MSL variation. Having accounted for those covariables, extraneous factors impacting on the data-stream caused step-changes in 1997, 2009 and 2015.

Following Tropical Cyclone Justin in March 1997, a major dredging campaign removed 108,000 m3 of accumulated sediment from the harbour floor, which caused the wharf supporting the tide gauge to settle about 40 mm into the bed of the river by January 1998. Dredging of more sediment in 1999 (26,000 m3) did not affect the gauge. However, in March 2009 it settled a further 37 mm probably as a result of disturbances caused by TC Ellie (30 January to 4 February 2009) and TC Hamish (4 to 11 March 2009). The harbour was dredged again following TC Ita in 2014 (60,000 m3), then in January 2015 the former wooden wharf that supported the tide gauge was strengthened and re-decked with a new composite material capable of allowing small trucks to load and unload supplies ( Dredging and refurbishment caused the tide-gauge to settle a further 32 mm. Step-changes underlying the data-stream show the gauge is not well-secured to the harbour floor.

The highly significant step-changes (P <0.001) totalling 109 mm (SEM 9.4 mm) accounted for all the apparent MSL trend. There is no evidence therefore that sea level is rising in the northern sector of the Reef. The IPCC prediction that sea levels will increase globally by 26 to 29 cm by 2030 is an unlikely scenario.

A Queensland Government aerial photograph taken on 11 September 1969 was re-scaled and oriented so features across the peninsula east of Cooktown including the well-defined Cherry Tree Bay and associated rocky headlands can be directly compared as an overlay on a Google Earth Pro satellite image taken on 16 September 2018.

Marked where they intersect the headlands, tidal wetting fronts are the same along the low-gradient beach. Littoral zones around the headlands that define inter-tidal habitats also directly align. The same shoals and individual shore-line rocks, the small watercourse draining to the beach: all the same. There is no evidence of tidal encroachment and therefore no evidence that sea levels have materially changed over the intervening 49-years (Figure 2).

What we conclude      

Satellite data depended upon by IPCC do not stack-up with tide gauge data or aerial photographs taken between 1969 and 1994 compared with high-definition Google Earth Pro Satellite imagery of the same sandy-beach.

It seems that while CSIRO et al. can model sea level relative to some point at the centre of the earth with mm/year precision using satellites traversing the same patch of heaving ocean every 20-days or so, they and other oceanographers and elite climate scientists lack the skills to analyse tide gauge records or interpret aerial photographs they can freely download from the internet.     

Satellite data upon which speculation relating to sea level rise depends, is pre-loaded with trend and should not be used for critical studies, for spreading alarm or for informing government policy. It is a ridiculous notion that sea levels will increase by almost 300 mm during the next 9-years.

Figure 2. Aerial photograph of Cherry Tree Bay, east of Cooktown taken on 11 September 1969 overlaid on Google Earth Pro (GEP) Satellite image for 16 September 2018; upper-left, GEP opacity 0%, 50%; lower-left 75%, 100%. Tidal wetting fronts, littoral zones, rocks and shoals show no encroachment or change in exposure due to rising sea levels over the intervening 49-years.

 To access full paper in downloadable PDF form, click here

To access full table of data supporting the paper, click here

Trends in sea level at Townsville, Great Barrier Reef

Sea level at Townsville, Great Barrier Reef, Queensland

Dr. Bill Johnston[1]


Main points

  • If melting of glaciers and icesheets in Greenland in recent decades significantly influenced mean sea level (MSL) it would be detectable in data for Cape Ferguson from 1991 and Townsville Harbour from 1959. However, there was no evidence that climate change, warming or melting ice sheets has caused sea levels to increase.
  • Tide gauges are affected by the conditions under which they operate. Data are coarse, imprecise, poorly documented and not understood by climate scientists and oceanographers who routinely conflate variation caused by covariates such as the El Niño Southern Oscillation, components of local water balances, and step-changes caused by site and instrument changes as being due to the climate.
  • In order to draw valid conclusions, it is imperative that scientists implement a quality assurance process that distinguishes between variables that cause variation IN data (covariables), from those that impact ON the data-stream (impact variables) and adjust for those using independent statistical methods.
  • Scores of peer reviewed papers published at great expense in elite scientific journals, by multiple authors supported by long reference lists are biased by lack of attention to detail and poor science. Using Cape Ferguson as a case study, and replicated using data for Townsville Harbour, the approach outlined here, which is widely applicable, sets a benchmark for undertaking due diligence on data. Findings of papers that failed to assess the fitness of data used to determine trend and change should be disregarded.


Australia’s lead management agency for the Great Barrier Reef, the Great Barrier Reef Marine Park Authority (GBRMPA) states on their website that “global average sea level rose by 0.18 centimetres per year from 1961 to 2003. The total rise from 1901 to 2010 was 19 centimetres, which is larger than the average rate during the previous 2000 years.” (

Further, they say that “Since 1959, records of sea levels for Townsville, in north Queensland, show an average increase of 1.2mm per year. However, the rate of increase may be accelerating, with records of sea levels at Cape Ferguson near Townsville showing an average increase of 2.9mm every year between 1991 and 2006.” How can it be that for the same waterbody, sea level is increasing 2.5 times faster just 25 km away from Townsville Harbour at Cape Ferguson?

GBRMPA goes on to claim that “because much of the land adjacent to the Great Barrier Reef is low-lying, small changes in sea level will mean greater erosion and land inundation. This will cause significant changes in tidal habitats, such as mangroves, and move saltwater into low-lying freshwater habitats. This will have flow-on effects for juvenile fish that use these habitats for protection and food resources.” So how can that be that compared with current satellite imagery aerial photographs from the 1950s and 1960s show wetting fronts on beaches and tidal influences on rocky headlands such as Cape Cleveland are unchanged?

Paid for by taxpayers, led by government agencies including CSIRO and the Bureau of Meteorology, ably assisted by the Australian Institute of Marine Science (AIMS) and barracked-on by slick campaigns run by WWF, the Climate Council, the Australian Museum, the Great Barrier Reef Foundation et al., Australians are bombarded by confusing, over-hyped mis-information and scare-campaigns related to the Great Barrier Reef.

Disaster-porn has replaced knowledge and understanding to the point that Australia’s climate history has been substantially re-written. Like a billion-dollar cart of hay put before the science-horse, in almost every sphere, policy-driven science has overtaken the scientific method.

Coupled with previous exposés that showed apparent trends in maximum temperatures at Cairns, Townsville and Rockhampton were caused by homogenisation adjustments and not the climate [LINK], this series of investigations examines monthly sea-level data measured at Cape Ferguson since September 1991 and the longer record for Townsville Harbour since January 1959. The aim is to independently verify that due to anthropogenic warming, survival of the Great Barrier Reef is imperilled by compounded multiple threats including sea-level rise. Of overriding concern is that on behalf of their ‘independent’ boards and sponsors, scientists may have been led astray by liberally-scattered golden-hay, and thereby lost pride in their scientific work.

What we did

Using the 30-year monthly MSL dataset for Cape Ferguson as a case study, we objectively distinguished between variables that cause variation IN tide-gauge data (covariables) from those that impacted ON the data-stream (impact variables). The approach outlined in the paper provides climate scientists and oceanographers with a method for verifying that data they use is fit for purpose i.e., that trend reflects the oceanographic waterbody and not covariables and/or effects caused by site and instrument changes. The Cape Ferguson study was replicated using the 62-year monthly dataset for Townsville Harbour.

Principle findings

  • At Cape Ferguson, 31.9% of variation in MSL was accounted for by (in order of importance), SOI3pt; barometric pressure (hPa); lag1 solar exposure (MJ/m2); Lag2 rainfall (mm), and current rainfall. Accounting for a step-change in 2009 caused by a change in calculating 10-minute values from 1‑second samples, and a residual 18.06-year cycle, increased R2adj to 0.645 (64.5%). Having removed variation IN the data and the effect of the inhomogeneity ON the data-stream, no trend or change was attributable to any latent factor such as melting glaciers and icecaps in Greenland, coal mining or global warming. 
  • The dataset for Townsville Harbour from January 1959, was nosier than Cape Ferguson, partly because data before 1984 were manually digitised from tide gauge charts and also because water levels in the harbour, which lies at the entrance to Ross Creek are greatly influenced by hydrological processes within the catchment, including urban development, irrigation, leakage etc. Thus, while SOI3pt was less influential, components of the water-balance (rainfall, evaporation and seasonality) were more so. Significant covariables accounted for 25.3% of variation in MSL.

Step-changes in residuals aligned with construction of the Ross River Dam in 1971 and its enlargement 2007. A third inhomogeneity in 1987 may have been associated with harbour developments or an undocumented change related to the gauge. Significant variables and step-changes together accounted for 49.2% of MSL variation.

  • Although MSL data were affected by random noise no residual trends or changes were due to any other systematic factor including warming of the climate or the ocean.

The full report can be downloaded [HERE].

[1] Former NSW Department of Natural Resources research scientist.