Now, do not misunderstand me. I am not a ‘climate change denier’ or ‘sceptic’ or what ever appellation you might like to add. In fact I would be more surprised if the climate did not change. After all, it has changed many times over the millennia. The last major cooling—‘The Ice Age’, came to an end some 10,000 years ago, as the climate changed and the polar ice caps started receding. They have been receding ever since, but with a few very marked reversals. There was a major period of cooling some 2,500 years ago, between the Bronze Age and the Iron Ages. There was a significant, but somewhat less drastic, period of cooling in the mid 1500’s, and several others since. Each of these were preceded and followed by periods of warming. So, climate change is nothing new, and there are no reasons why we should expect the climate to remain perfect for we humans for all time.
But, when I read or hear what the climate change evangelists have to say about the effects of climate change, I have a great deal of difficulty in knowing what to believe and what not to believe. One matter in particular which gives me a great deal of concern is that of the predictions of rising sea level. Last week I heard Sir David Attenborough refer to ‘a rise of the order of one meter’, and some time ago the Australian environmentalist Dr Tim Flannery referred to ‘a rise of the order of seven meters’. We also hear the concerns of some Pacific Island nations that their islands ‘are already sinking because of rising sea levels caused by climate change’.
Dealing with this last statement first, I do not see how the sea level can be rising significantly in one part of the Pacific, but no-where else. There certainly has not been a measurable increase, for example, around the coast of Australia or New Zealand that I am aware of or that has been reported as a matter of concern. I accept that there may be unusually high tide surges, caused by climatic conditions, but as far as I can make out, no actual rise in sea level generally. My personal view of the plight of the Pacific Islands is that they are on the northern edge of the Indo-Australian tectonic plate which is sub-ducting under the Pacific Plate, and as a consequence, those islands are actually sinking. If this is correct, then no amount of action on climate change can save them from extinction.
Back to the more general issue of rising sea level. Many coastal community Councils are now introducing planning regulations which prohibit new buildings too close to the sea. This is largely a self-preservation stance, to guard against future legal problems if indeed the sea rises and engulfs coastal communities. As an aside, one major project currently under construction in Victoria which seems to have escaped these new planning regulations is the de-salination plant near Wonthaggi. This is being built at sea level, with only a sand dune between it and Bass Strait, and would be extremely vulnerable in the event of major sea level rises! But what is the reality of the risk?
To me it is a matter of simple arithmetic. According to Encyclopaedia Britannica, the total area of the earth is just over 500 million square kilometres. Of this, some 149 million is land, and 361 million is water. So as not to have to add too many zeros, I shall use the convention for these and the following numbers of 500×106 , 149×106 and so on. These areas are in square kilometres, and so to put them into square metres, it is necessary to multiply each by 1 million. Thus the area of the sea is 361×1012 sq m. and in order to increase sea level by 1 metre it will be necessary to add 361×1012 cubic meters of water from some source. The polar ice caps are the favourites to provide all the extra water. The problem is that the north polar ice cap is actually floating, so however much ice there is, 90% of it is already being included in the current total of ocean water and if it all melts, will not significantly increase the levels. Next time you have a scotch or gin and tonic, note carefully the level of the drink in the glass before the ice cube melts, and again when it has melted. Assuming you have not actually consumed any of the drink, you will note that the level in the end is not significantly different to that at the start. And so it is with the north polar ice cap.
The Arctic ice sheet is approximately 15×1012 sq m, with an average thickness of the order of 5 metres,—but remember that this ice sheet is floating, and any ice under the sea, about 90% of it, is already contributing to the current sea level. So, the volume of ice which, if it all melted, would add to the total oceanic water is (15 X 1012) X 0.5 which comes to 7.5 X 1012 M3. But as we have noted, it would need 361×1012 M3 to increase the level by a meter. So clearly the north polar ice cap is not going to be a significant contributor.
The south polar ice cap is largely “one year ice” which means that most of it melts into the ocean and is replaced each year. So, if it all melted but was not re-frozen the resulting sea levels would only be those that are recorded at the end of every Antarctic summer—hardly an additional meter across the globe.
Other sources of melt-water are glaciers etc, but the total volumes contained therein are not really significant if spread over the total area of the world’s oceans.
So, why do carbon emission evangelists continue with their grossly exaggerated predictions of sea-level increases? One can only assume that either they have not done the maths themselves and just go along with what they are fed by their high priests, or that they are simply trying to scare everyone into accepting carbon taxes and emission trading schemes for reasons of their own.
In a future Blog, I shall have a look at the phenomenon of “natural” v “man-made” approaches to climate change and other global events. In the meantime, I would be delighted to hear from anyone at all who believes my reasoning on the melting ice matter is incorrect. I would also be happy to hear from anyone who thinks I am correct
Slingsby Browning
February 19, 2012
Slingsby's Miscellany 
I think your argument about the Arctic Ice is slightly incorrect, but in a way that supports your argument even more strongly.
The reason why ice floats in water is because it is less dense than water, roughly 10% less dense. This means that floating ice occupies roughly 10% more volume than does the water displaced by the ice’s total mass (Archimedes’ Principle at work here – the volume of water displaced is equal in mass to the weight of displacement). So, when a mass of ice melts to become the same mass of water, it loses its excess volume (i.e., it shrinks) and becomes identical in volume (and density) to the volume of water that it previously displaced. This means that melting ice makes absolutely no difference to sea levels if the ice was originally floating in the ocean.
However this still isn’t quite correct, but this time in a way (a very tiny way) that would run counter to your argument. If the ice is pure frozen water, then the volume of seawater that it displaces will be less in volume than the volume occupied by the pure water generated by the melting ice. This is because seawater has a higher specific gravity (higher mass per unit volume) than does pure water by a factor of about 2.5%. So, if pure floating ice melts into seawater, it will occupy roughly 2.5% more volume than the volume of seawater it was originally displacing, thereby raising sea levels. So, instead of adding 7.5 x 10^12 cubic metres of volume to the oceans (according to your original calculation), it’s only about one quarter of that to worry about (i.e., 2.5% is 1/4 of the 10% that you originally calculated). So, the volume to worry about would be approximately 1.9 10^12 cubic metres, which, being such a tiny fraction of the 361×10^12 cubic metres required to increase sea levels by 1 metre, would only increase sea levels by roughly 5.2 millimetres!
Even so, that’s not quite the end of the matter, because pure water melting into sea water would raise the local water vapour pressure of the ocean surface, thereby increasing local evaporative loss of oceanic volume into the atmosphere. This tiny effect will further reduce the estimate of rising sea levels. There may also be other complicating factors that I haven’t taken into account here. It would be interesting to know what the climate modellers would have to say.
Incidentally, mention of water vapour pressure in the last paragraph reminds me of something that troubles me about all the concern we hear about so-called greenhouse gases such as water vapour and carbon dioxide. Increased atmospheric concentrations of these are claimed to increase global warming. But the oceans are vast reservoirs of water (obviously) and dissolved carbon dioxide. Warming of the oceans will cause the oceans to lose even more water vapour and release carbon dioxide into the atmosphere, generating more ‘nasty’ greenhouse gases. Therefore, given such relationships, the system seems inherently plagued by positive feedback and should be inherently unstable, oscillating uncontrollably between extremes of global warming and global freezing. But this clearly doesn’t happen. Why? Are the stabilising mechanisms known and have they been built into the climate change models?