LETTER: Two readings from a century-long database are inadequate

DEAR News Of The Area

I WRITE with reference to the opinion of Mr Michael Ferris (‘Are our seas really rising?’, NOTA, 27/8/26) and the comments made by Mr Iain Watt, may not be correct and that the seas are not rising.

Mr Ferris cites his opinion and information is backed by a registered Oceanographer and Hydrographic surveyor. Physical oceanographers study movements like waves, tides, and ocean currents, plus how the ocean affects the weather.

A hydrographic surveyor measures and maps underwater physical features, such as the shape of the seabed, water depths, tides, and currents in oceans, rivers, and lakes.

Neither measures sea level.

Sea level is measured by two main methods: tide gauges and satellite altimeters.

Tide gauge stations from around the world have measured the daily high and low tides for more than a century, using a variety of manual and automatic sensors.

Using data from scores of stations around the world, scientists can calculate a global average and adjust it for seasonal differences.

Since the early 1990s, sea level has been measured from space using radar altimeters, which determine the height of the sea surface by measuring the return speed and intensity of a radar pulse directed at the ocean.

The higher the sea level, the faster and stronger the return signal is.

Global Measurements (Satellites) Radar Altimeters Satellites hundreds of miles above Earth send microwave pulses down to the ocean and time how fast they bounce back.

Orbiting instruments map the entire planet’s ocean height every few days to calculate overall trends.

Local Measurements (Tide Gauges) Acoustic and Radar Sensors: Modern stations use sound waves or microwaves attached to piers to measure the distance down to the water surface.

Pressure Sensors are underwater tools that measure the weight and pressure of the water column above them to track height.

Early methods used simple marked rulers or floating pens on rotating paper drums.

Mr Ferris, in use of two and only two data points from over a century-long database, strains credulity.

I would suggest he avails himself of the data set available at National Oceanic and Atmospheric Administration website (Climate Change: Global Sea Level Rebecca Lindsey published August 22, 2023).

Regards,

Mervyn McConnochie,

Karuah.