Adonis Diaries

Archive for April 4th, 2013

Upper Ocean Heating up? How this phenomenon was measured?

How  can you convert or transform heat graphs into temperature graphs?

I love graphs: They tell more stories than a thousand pictures and hundreds of lectures. I failed to copy the graphs this time around, but you may access them if you care: There are other purposes in that post.

Willis Eschenbach guest posted on February 25, 2013 under “Ocean Temperature And Heat Content”

“Anthony has discussed the latest findings regarding the heat content of the upper ocean.

He notes that there has been no significant change in the Ocean Heat Content OHCA in the last decade. It’s a significant piece of information.

I still have a problem with the graph, however, which is that the units are meaningless to me. What does a change of 10 zeta-joules mean?

I converted the graph to a more familiar units, degrees C. Let me explain how I went about that.

To start with, I digitized the data from the graph. Often this is far, far quicker than tracking down the initial dataset, particularly if the graph contains the errors.

I work on the Mac, so I use a program called GraphClick and measured three series: the data, the plus error, and the minus error. I then put this data into an Excel spreadsheet.

All that remained was to convert the change in zeta-joules to the corresponding change in degrees C. The first number I need is the volume of the top 700 metres of the ocean. I have a spreadsheet for this.

Interpolated, it says 237,029,703 cubic kilometres. I multiply that by 62/60 to adjust for the density of salt vs. fresh water, and multiply by 10^9 to convert to tonnes.

I multiply that by 4.186 mega-joules per tonne per degree C.

That tells me that it takes about a thousand zeta-joules to raise the upper ocean temperature by 1°C.

Dividing all of the numbers in their chart by that conversion factor gives us their chart, in units of degrees C. Calculations are shown on the spreadsheet.

Figure 2. Upper ocean heat content anomaly, 0-700 metres, in degrees C.

I don’t plan to say a lot about that, I’ll leave it to the commenters, other than to point out the following facts:

1. The temperature was roughly flat from 1993-1998. Then it increased by about one tenth of a degree in the next five years to 2003, and has been about flat since then.

2. The claim is made that the average temperature of the entire upper ocean of the planet is currently known to an error (presumably one sigma) of about a hundredth of a degree C.

3.  I know of no obvious reason for the 0.1°C temperature rise 1998-2003, nor for the basically flat temperatures before and after.

4. The huge increase in observations post 2002 from the addition of the Argo floats didn’t reduce the error by a whole lot.

My main question revolves around the claimed error.

I find the claim that we know the average temperature of the upper ocean with an error of only one hundredth of a degree to be very unlikely. Doubtful. Why?

The ocean is huge beyond belief and this claimed ocean error is on the order of the size of the claimed error in the land temperature records, which have many more stations, taking daily records, over a much smaller area, at only one level.

I also find it odd that the very large increase in the number of annual observations due to the more than 3,000 Argo floats didn’t decrease the error much …

As is common in climate science … more questions than answers.

Why did the temperature go up?

Why is it now flat?

Which way will the frog jump next?

Note: Figure 1. Upper ocean heat content anomaly (OHCA), 0-700 metres, in zeta-joules (10^21 joules). Errors are not specified but are presumably one sigma. SOURCE




April 2013

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