“Things you know that ain't so - the sea level is rising rapidly and this will continue to increase”.
We are constantly being told by the Royal Society of New Zealand and others that the sea level is rising more and more rapidly and we must be prepared for a rise of something like 1 m over the next 100 years or so – 10 mm per year. This is a serious matter because many Councils are now restricting building close to the sea and putting restrictions on existing houses that have substantially reduced their value.
There is no scientific foundation for this belief. It is based on the output of computer models that, so far, have been shown to consistently overestimate the rate of sea level rise.
So what do we know about sea level rise?
There are two ways of measuring sea level rise.
One is from the records of tide gauges spread around the world. The oldest records date back to the 1890s and, the average rise for 225 tide gauges spread around the world is 1.48 mm per year.
This is close to the generally accepted 1.72 mm per year for tide gauges.
In the 1990s, Australia set up a series of very accurate tide gauges all around Australia and on many Pacific Islands. These show that, for the majority of sites, the sea level rise since the mid-1990s was less then 2 mm per year.
The Pacific Islands record shows, for instance, that the sea level in Tuvalu has hardly changed since 1992. At the moment, as a result of the current El Niño, Tuvalu sea level is about 100 mm below the level in 1994 – 1997.
According to "Sea level rise – history and consequences” by Bruce Douglas there has been no acceleration of the rate of rise during the 20th century.
The other source of sea level rise data is from satellite observations. These show a reasonably steady rise of about 3.2 mm per year. Nobody seems to be able to explain the difference but it is possible that it is due to warm patches in the middle of the ocean increasing the oceanic sea level. Many "climate scientists” have cobbled together the tide gauge and satellite records and used the result to claim that the rate of rise is increasing. This is, of course, highly unscientific.
Predictions of sea level rise from IPCC computer models range from about 150 mm to 300 mm by 2100. In 2011, NASA’s predictions ranged from 200 mm to 700 mm. At the present rate of rise the figure would be 125 mm.
The Ministry for the Environment has cobbled the satellite record onto the tide gauge record and predicts a sea level rise of something like 0.5 m to 0.8 m by 2100. But, to its shame, the Royal Society of New Zealand leads the pack with a projected rise of .3m to 1 m. More than anybody else!
So there we have it! All the evidence indicates that the sea level is likely to rise 100 to 200 mm by 2100. But the government, the Royal Society and other public bodies choose to believe the predictions of the sea level models that have been spectacular failures so far and, as a result, are devaluing coastal properties and preventing development in places where, in all probability, there would be negligible risk for hundreds of years.
So blind belief in flawed computer models overrules the evidence. And coastal communities pay.