Guest Post by Willis Eschenbach
Anthony has an interesting post up discussing the latest findings regarding the heat content of the upper ocean. Here’s one of the figures from that post.
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
He notes that there has been no significant change in the 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? So following my usual practice, 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, I’m sure the same or better is available on the PC. I measured three series: the data, the plus error, and the minus error. I then put this data into an Excel spreadsheet, available here.
Then 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 whole lot about that, I’ll leave it to the commenters, other than to point out the following facts:
• 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.
• 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.
• I know of no obvious reason for the 0.1°C temperature rise 1998-2003, nor for the basically flat temperatures before and after.
• 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 in this 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 … the ocean is huge beyond belief. 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. Doubtful.
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 it go up? Why is it now flat? Which way will the frog jump next?
Regards to everyone,
w.
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Hey, a broken clock constantly reports very reproducible values. Doesn’t mean it’s accurate.
Many thanks indeed !
That claim of ‘error knowledge’ should be voided as well as the ‘0.1’ of a degree C increase.
XD
Read Tisdale.
re the “the 0.1°C temperature rise 1998-2003”. Could it be from the 1997-8 El Nino? If the upwelling warm water comes from below 700m depth, or if the temperature measure doesn’t treat all 700m equally, it could be the El Nino. I think this would be in line with Bob Tisdale’s thinking that there is a ‘step function’ at an El Nino.
Willis,
” 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 … the ocean is huge beyond belief. 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. “
But the ocean temperature isn’t noisy. At depth there is no daily variation – and weak spatial gradients. There are no winds, no variable sunlight. The main issue seems to be deciding where the float actually was when readings were taken.
Here is a document that looks at a particular trajectory in detail. Fig 8 in particular shows the error issues.
I am always interested in error bars. I suspect that they are not really wanted and everyone in the modelling world would be happier if they would just disappear but stubbornly refuse to do so. They are cleaned up and brought out for show when they need to be accounted for by they are expected to behave themselves, not make a scene, not speak unless spoken to and certainly not relax and reveal any more of themselves that strictly necessary.
In reality if they were allowed to be themselves and behave as they would at home I suspect that the error bars would undo their corsets and belt buckles and flop out all over the place.
This would then spoil the image of the neat, tidy, prim and proper graph because it would be indistinguishable from a page of wall to wall error bars running rampant. A bit like a ball room dancer at a Hells Angels long weekend booze up.
• I know of no obvious reason for the 0.1°C temperature rise 1998-2003, nor for the basically flat temperatures before and after.
Adjustments to the bathythermograph fall rate (particularly for the data from 1996)?
http://www.nodc.noaa.gov/OC5/WOD09/bt_bias_notes.html
DOH! You’ve change a heat content measurement of the entire ocean to a level of abstraction, a potential to reach a certain temperature at a specific depth. Not an improvement.
First: Bob Tisdale explains with clarity what happens with ENSO and step changes.
Second: What happened to the water energy below 700meters? Any mixing there could have tremendous affect.
Anyway – the earth seems particularly stable with regard to its energy budget based on your fine work Willis. One caveat is that the measurements to be accurate with such tiny variations seems difficult at best to measure. I personally have found it difficult to get such accurate and repeatable measurements from temperatures sensors, even with RTDs… you know those platinum ones…
First: Bob Tisdale explains with clarity what happens with ENSO and step changes.
Second: What happened to the water energy below 700meters? Any mixing there could have tremendous affect.
Anyway – the earth seems particularly stable with regard to its energy budget based on your fine work Willis. One caveat is that the measurements to be accurate with such tiny variations seems difficult at best to measure. I personally have found it difficult to get such accurate and repeatable measurements from temperatures sensors, even with RTDs… you know those platinum ones…
Great post!
@James Baldwin Cook: No, he converted energy budget to an average temperature increase in a normalized body of water equal to the volume reported. It helps us see what the magnitude of the energy budget would do to the ocean temperatures of that upper 0.7km of ocean. It’s just to put things into perspective.
@James Baldwin Cook: No, he converted energy budget to an average temperature increase in a normalized body of water equal to the volume reported. It helps us see what the magnitude of the energy budget would do to the ocean temperatures of that upper 0.7km of ocean. It’s just to put things into perspective James…
Nick,
Ya, you’d be amazed if you look at a ships track over time in ICOADS by how little it changes and by how little it changes during the course of a day.. relative to the air that is.
@Willis:
“• 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.”
Actually, that is not what the number represents.
REPLY: Mosh – instead of making another crypto-comment, why not tell us what it represents and show a citation? – Anthony
Thanks Hoser i had a good laugh at that, I use it often and chuckle every time.
James Cook says:
February 25, 2013 at 11:02 pm
Thanks, James. “Potential to reach a certain temperature”? I did several things, but I’ve no clue what you are referring to.
w.
Willis, with N randomly sampled observations the standard error equals the standard deviation times square root N. Standard error 0.01 and N = 3000 suggests standard deviation of half a degree Celsius or almost all annual means (per float) between plus/minus one degree. Crucial is randomness. Is there also a graph of number of floats each year? If not fixed, for each year the number added and the number deleted? The whole effect may be due to sample change. Compare the surface station record.
The temperature rise from 1998 – 2003 is when the Argo system was being deployed. The slightly lower earlier temperatures most probably represent nothing more than some attempt to adjust for the depth/time error inherent in XBT temperature profiles.
The brief 1993 to 1997 part of the record is only enough to indicate a steep rise thereafter but too short to raise uncomfortable questions regarding the earlier decades of no noticeable increase.
It is notable that two incompatible measurement systems are brought together in this graph. Is it coincident that the (relative) warming spurt occurred on the eve of commencement of the ARGO floats?
We’ve seen this before, when sea level rises doubled at the time measurements glissaded from tide gauges to satellites, around 1992. And when hockey sticks glissaded from paleo measures to instruments around 1960. And … ?
Most solar input occurs above the thermocline. Actually, almost all solar energy input occurs within the top meter of the ocean depth. That one meter of ocean has over 3000 times the volumetric heat capacity of the air above it. Most of the global energy budget therefore arises at the tropical ocean surface. The greatest variable affecting that budget is how much solar energy reaches the surface. Since tropical ocean albedo is very low, the only remaining major variable is the transparency/albedo of the atmosphere above the ocean, ie clouds.
Another variable is how much mixing/transport occurs from the ocean surface downward.
The thermocline is usually around 100 meters. Below the thermocline, the ocean depths are pretty much an infinite heat sink. Even relatively small changes in surface currents will carry more thermal energy than the entire atmosphere above the surface. What would happen to the northern polar ice if there were a small shift in the direction of the Gulf Stream??
Does any one how much energy it takes to heat 237 million cubic kilometers of salt water by 0.1 deg in 5 years. Is it possible given heat from the sun and from the earths core (volcanos etc)
PaulC says:
February 25, 2013 at 11:57 pm
Does any one how much energy it takes to heat 237 million cubic kilometers of salt water by 0.1 deg in 5 years. Is it possible given heat from the sun and from the earths core (volcanos etc)
___________________________
The graph says it is possible. Maybe we could get some models to agree. Maybe I should just go back to sleep.
Luther Wu says “The graph says it is possible
That’s the point – the graph looks wrong. A out of character step usually means Mann made figures.
The oceans have currents …. with areas of cold upswelling. You dump floats in the sea and it is a matter of fact that they will float away from the areas of upswelling from cold->warm..
Sorry, I meant above standard deviation divided by square root N. An example of simple book-keeping you almost never see. GHCN: 1940 has 4266 stations, 1940-1969 added 6074, deleted 696. In 1970 we have 9644 stations, 1970-1999 added 2918, deleted 9434. In 2000 we have 3128 stations, 2000-2010 added 14, deleted 1539. The samples were never spatially random. The changes were extremely non-random (homogenization). If something similar happened with the floats, the whole effect is dubious beyond repair.
Nick said;
‘At depth there is no daily variation – and weak spatial gradients. There are no winds, no variable sunlight. The main issue seems to be deciding where the float actually was when readings were taken.’
Can you give us your definition of ‘depth’ in the context you are using i? Self evidently there is a huge difference between the top and bottom of the ocean and sufficient spatial gradient to make it worth thinking of tapping into it as an energy source. The temperature difference will vary of course according to if you are in the tropics or Northern:Latitudes.
Are you referring purely to abyssal depth?
tonyb