Quantifying Sea Level Fall

Guest post by David Archibald

The background to this is that, in 2009, evil environmentalists in the New South Wales Government made a regulation that councils in that state would have to base their building permits on an expected sea level rise of 900 mm by 2100. This had the effect of wiping billions of dollars off the value of coastal properties, as well as ruining peoples’ lives etc. By comparison, sea level rose 200 mm in the 20^th Century.

The NSW Govt. regulation was gleefully enforced by Lake Macquarie Council to the detriment of its residents. Lake Macquarie is 140 km north of Sydney. In response, a local property developer, Mr Jeff McCloy, organised a public meeting at which Professor Ian Plimer, Professor Bob Carter and myself spoke. 400 people attended on four days’ notice. The subject of the public meeting was sea level rise.

Before we go on to the oceans, let’s start with a smaller body of water first – Lake Victoria in East Africa. It was known back in the 1920s that the level of Lake Victoria went up and down with the solar cycle. This is the data on the level of Lake Victoria from 1896 to 2005:

The relationship with solar activity broke down in the 1930’s and resumed in the 1970’s. There was also a very rapid rise in the 1960’s. Taking out the period of the solar relationship breakdown and detrending the data from 1968, this is what the relationship looks like (data courtesy of Dr Peter Mason):

There is no doubt about the relationship between solar activity and the level of Lake Victoria, which also means that East Africa has about 30 years of drought ahead of it based on what is going to happen to solar activity.

Some may remember this post from 2009: http://wattsupwiththat.com/2009/04/07/archibald-on-sea-level-rise-and-solar-cycles/

which contained this graph:

That has now been updated as:

The good correlation between sea level rise and solar activity is evident. What is very interesting is that during four solar minima over the 20^th Century, sea level fell during those minima. That means that during prolonged low solar activity, sea level can be expected to continue falling. That relationship is quantified in this graph:

Using the period of best fit from 1948 to 1987, the relationship between solar activity and sea level is found to be 0.045 mm per unit of sunspot number. The threshold between rising and falling seal level is a sunspot amplitude of 40. Below 40, sea level falls. Above that, it rises. We can now combine that with Livingston and Penn’s estimate of Solar Cycle 25 amplitude of 7 to derive this graph of seal level rise from 1870 with a projection to 2040:

Sea level has a few more mm of rise to the maximum of Solar Cycle 24 in 2013 and then will fall 40 mm to 2040 taking us back to levels of the early 1990s.

Now back to the subject of Lake Macquarie: the nearest high quality sea level data is from Fort Denison in Sydney Harbour. This is the record from 1915 to 2009:

The rise over the 20^th Century has been slight, so slight that it can be compared to human hair which on average is 0.1 mm thick. The rise has been an average of 5 human hair widths per annum, with most of that over 60 years ago. Let’s compare that with what the NSW Govt and Lake Macquarie Council are projecting for the 21^st Century:

I have called sea level rise the second last refuge of the global warming scoundrel, with ocean acidification being the last refuge. It no longer provides any refuge now that the relationship with solar activity has been quantified.