Saturday, 19 July 2014

Sea Level and Ice Melt

Both present sea level rises and ice melt are well documented but it has been claimed (by some) that this information has been misleading or scaremongering. Is this claim justified?

Predicted sea level rise.
Here is “my prediction” (figure 1) of sea level rise by the year 2100.Useless isn’t it?

Figure 1 A prediction of sea level rise.

I am using the estimate for the average depth of the oceans to be 14 000 feet ( I think you will agree that my graph above (figure 1) is quite useless, unless my intent was to say don’t worry sea level is hardly going to rise. From the graph you may be hard pressed to say the increase was somewhere between 0 and 2%. That is somewhere between 0 and 280 feet; somewhere between no ice melting and all the ice on Earth melting. This is not the way to present data and so here (figure2) is the data presented in a way that is meaningful:-

Figure 2 Present rates of sea level rise. (July 2014  Nasa)

Using this information you can easily work out that if this present trend continues, without further acceleration, the sea level will rise by about 27 cm by year 2100. (This is at the lower end of the recent IPCC report 2013).

Presentation of data.
I think you will agree that the NASA presentation of data is far more useful than the kind of presentation depicted in figure 1. Most people are not really interested in the average depth of the ocean or have any natural “feel” for the significance of this. However sea level rise above what we experience is easily understood. Surely if one were to argue that the data should be presented as in figure 1, looking at the whole depth of the ocean, then it would get little support. However this is the type of claim being made here by  E. Calvin Beisner and J.C. Keister posting on WUWT.

Ice melt.
Unlike sea level, people in general don’t have an intuitive feel for either the total amount of land ice (on Greenland, Antarctica and mountain glaciers), or the amount of ice that is melting.  Thus claims that information on ice melt being hyped up may be believed by the casual reader, whereas if we use the same reasoning to sea level rise the claim would be easily spotted as unjustified. The Land ice melt information from NASA is given below. (figure 3)

Figure 3 Land Ice

Choice of presentation.
The data should be presented in such a way that it useful. Claiming that this sort of information as given in figure 3 is “lying with statistics” where information (which shows ice anomaly) is easily obtained, should really be compared to the proposed presentation as given in the form of figure 1 (which shows absolute values). This later form of presentation, exemplified by figure 1, can lead the reader to believing there is nothing to be concerned about whether there is or isn’t a case for concern.

I think if the National Climate Assessment or NASA presented their data in the way suggested by  E. Calvin Beisner and J.C. Keister it would be quite rightly criticized. It seems that the claim of “playing with Statistics” could be more appropriately aimed at the writers of this claim. These writers would seem to prefer the data to be presented in a way that no useful information could be obtained; no way of seeing if the data was consistent with other data; and no indication of whether there was need for concern or not.

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