Email 536 An excerpt of email from David Thompson of Colorado State to Phil Jones:
…As for the dip in 1945. After iterating with John Kennedy, it appears that the dip in 1945 corresponds to a sudden drop in US measurements in Aug 1945 (the US measurements were known
to be biased warm, so the cooling is consistent with the loss of US data). But it is also now clear that the SST is fraught with many instrument changes between the 30s and 1961. So
a conclusion we’ll likely make is that the trend in SSTs between 1900 and the present is reliable, but the behavior of the time series from the 1930s to the 1960s is not.
That the data are so unreliable between the 30s and 60s means we don’t know for sure what happened in terms of global-mean temperatures during that period. In fact, if you blank out the data from the 30s to the 60s, you can actually imagine the globe warming weakly but continuously during that period…
Hence, the only real evidence we have of a midcentury about-turn in global warming comes from the land data.
Full email
date: Tue, 27 Nov 2007 10:48:58 +1100 from: David Thompson <davet@atmos.xxxxx> subject: a quick comment and a quick question to: Phil Jones <p.jones@uea.xxxx> Phil, The comment…. Thanks for the thoughts on the volcano plots. I’ve spent the last few days playing with different analyses, and I think I’m converging on the main points to make in the paper. It’s my impression that almost all aspects of the volcanic signal have been discussed in the literature, except for the longish timescale suggested by the residual data and the detrending. For sure the timescale is sensitive to the detrending, and I’ll be very careful about that in the writing. But I think using the residual data we can get folks chatting about the possibility that volcanoes impact SSTs much longer than the ~2-4 years suggested by the current literature. Anyway…. that’s how I’m leaning on the results. I should have some text ready soon… The question…. As for the dip in 1945. After iterating with John Kennedy, it appears that the dip in 1945 corresponds to a sudden drop in US measurements in Aug 1945 (the US measurements were known to be biased warm, so the cooling is consistent with the loss of US data). But it is also now clear that the SST is fraught with many instrument changes between the 30s and 1961. So a conclusion we’ll likely make is that the trend in SSTs between 1900 and the present is reliable, but the behavior of the time series from the 1930s to the 1960s is not. That the data are so unreliable between the 30s and 60s means we don’t know for sure what happened in terms of global-mean temperatures during that period. In fact, if you blank out the data from the 30s to the 60s, you can actually imagine the globe warming weakly but continuously during that period… Hence, the only real evidence we have of a midcentury about-turn in global warming comes from the land data. Are there any similar data issues in the land data during the period ~1939-1960? Thanks, Dave ——————————————————————– ——————————————————————– David W. J. Thompson www.atmos.colostate.edu/~davet Dept of Atmospheric Science Colorado State University Fort Collins, CO 80523 USA Phone: 970-xxx Fax: 970-xxx
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Anyone curious about the war-time variations should just look at the original ICOADS data. There was a one time increase (from one month to the next, no “trends”) in late 1941 . There was a roughly equal drop after the war. Again a step change from one month to the next.
In order to correct all that you simple need to subtract 0.24C for the duration of that interval , nothing more elaborate than what would be blindingly obvious to a school child.
http://oi43.tinypic.com/htyd61.jpg
changes in shipping caused an offset, so remove it.
If you do that the data seems to flow quite naturally across the whole period. There is NO inexplicable post war drop, just natural variation.
There is no anomaly. It was all a figment or their inept fiddling (well they would not have done that on purpose to give more post war warming would they?) . Inept fiddling that has not been corrected in last quarter century since it was introduced.
I have said it before and I’ll say it again, trying to derive a global mean temperature to look for global climate change using instruments meant to measure local weather is a fool’s errand. It is kind of as stupid as, I don’t know, using tree rings to figure out the past global climate.
The problem with sea surface temperatures, that is temperatures RIGHT AT the surface, is that if you increase wind speeds a little, it reduces the surface temperature by a lot. I would put more stock in temperatures at some depth below the surface. Actually, I would rather see temperatures measured in the abyssal deep. Those would have very little noise and a 0.1C temperature change over a decade would be significant but the logistics of measuring there is a huge problem. Sensors on undersea cables would probably be the best bet.
Tom says:
November 28, 2011 at 1:35 am
… Given that temperature varies over 24 hours in a roughly sinusoidal shape, taking the mean of the minimum and maximum as an approximation to the true mean is not so bad.
How bad is it? Quantify it. Spatially and temporally.
And when those happen to be the two data points that we have for a considerable portion of the temperature record, it is absolutely the right thing to do.
Is it? Or is is the absolute right thing to do: To admit that the data are inadequate for the new purpose – the purpose for which the data were not collected, the purpose that was not even conceived of when the data were collected.
The only question I have left is why it is still necessary to explain this to people. Yes, it might be better to have minute-resolution temperature data to construct accurate approximations to real means, but the bone-headed, bleedin’ obvious fact is that we don’t have it..
That we do not have what we need is not a justifcation for pretending that what we do happen to have is what we need. You are employing very faulty logic to avoid the necessity of having to “explain this to people”.
“That the data are so unreliable between the 30s and 60s means we don’t know for sure what happened in terms of global-mean temperatures during that period.”
In fact, I wouldn’t be surprised if it was actually a bit cooler than they’ve imagined it to be.
So now they’re trying to deny the dustbowl?
>> So now they’re trying to deny the dustbowl?
No, it’s a myth, it was all due to change from old fashioned dust sensors to modern electric ones. 😉
Tom says:
November 28, 2011 at 1:35 am
@Mark:
(((SNIP))))
The only question I have left is why it is still necessary to explain this to people. Yes, it might be better to have minute-resolution temperature data to construct accurate approximations to real means, but the bone-headed, bleedin’ obvious fact is that we don’t have it.
Do you always search for your keys under the lamp-post?
Atmospheric temperature does not equal atmospheric heat content and it is heat content we need to measure. So it might be better to have humidity and air temperature every hour at least and guess what? We actually have those metrics in many cases. At least we can _start_ gathering the data needed even if it was not appreciated in the 17th century that it was needed. Then we can estimate the average atmospheric heat content at each location every hour. It may well be that during the day temperature rises but heat content stays the same if the air becomes less humid. Why use incorrect metrics when you no longer have to?
The more we allow these individuals to adjust the records for “errors” and “step changes”, the more the temperatures over time are going to look like 4.3*ln(CO2current/CO2original).
Just leave everything the way it is.
If it continues warming, then we will know. We will not know anything if we let Mann, Jones, Karl and Kennedy continue adjusting the record. Pretty soon they will be just recording their climate model results instead of actual readings.
Dave’s email states:
This is perhaps the ignorance question of the day – but why/how were US measurement’s “biased warm” during that period, and how is that ‘known?’
Dave went on to say:
Perhaps only my cynicism speaking, but sure sounds to me like they are trying to eliminate the inconvenient mid-century cooling just as they tried to eliminate the MWP & LIA – or at least hoping to be able to come up with a way to do so.
crosspatch says
quote
I have a problem with sea surface temperatures anyway. Sea surface temps are often a wind speed proxy. Show me a temperature anomaly and I will generally be able to show you a wind anomaly.
unquote
Presumably the reasoning is higher windspeed = more evaporation and higher emissivity = lower temperature?
Why the blip? (If you haven’t seen it before, Google that phrase and Tom Wigley.)
JF
(I think i can do that as well….)
Serious discussion of the issue hasn’t even started if Earth Orientation Parameters (EOP) have not been mentioned. Trust obliterated.
“…As for the dip in 1945.”
Must have been that CO2: http://www.biomind.de/realCO2/bilder/CO2-MBL1826-2008-2n-SST-3k.jpg sarc/
There was a three-year strong El Nino from mid-1939 to the end of 1942. This was the longest El Nino on record. The AMO also spiked during the period which it often does in reponse to strong events. By 1946, they both crashed resulting in the rise then dip.
There are only two comparable periods when just as long ENSO events happened and these were both La Ninas. From 1970 to 1976 (the Great Pacific Climate Shift anyone) and the 1906 to 1911 period (1906 to 1911 was the coldest period in the 20th Century).
Just pointing out there are other explanations for large changes in the trends (and these do not have to be instrument errors).
This is a very serious issue, by far the most serious issue I have seen raised in any “climategate” thread. I will have more to say in the months & years ahead…
Tom says: November 28, 2011 at 1:35 am
Yes, it might be better to have minute-resolution temperature data to construct accurate approximations to real means, but the bone-headed, bleedin’ obvious fact is that we don’t have it.
But we do have actual MIN and MAX values to analyse for cooling/warming.
Analysing the mid-point between these two daily outliners is just crazy.
RE: P. Solar : (November 28, 2011 at 7:14 am)
“Anyone curious about the war-time variations should just look at the original ICOADS data. There was a one time increase (from one month to the next, no “trends”) in late 1941 . There was a roughly equal drop after the war. Again a step change from one month to the next.
“In order to correct all that you simple need to subtract 0.24C for the duration of that interval , nothing more elaborate than what would be blindingly obvious to a school child.”
Did they do this for the published HadCRUT and GISS data? As the war (World War II) went through several stages, I would be surprised if a single change would cover the whole period beginning in late 1939.
“…But the days grow short when you reach September.”
September Song — (used in a WW II documentary)
How well do we know the atmospheric pressures – say from the sea surface to stratosphere?
Are there any measurements by satellite?
RE: Agile Aspect: (November 29, 2011 at 3:16 pm)
“How well do we know the atmospheric pressures – say from the sea surface to stratosphere?
“Are there any measurements by satellite?”
These pressures can only be measured from aircraft. Weather balloons are also aircraft. In general, air pressure decreases exponentially with increasing altitude because of decreasing density (thinning out) with increasing altitude. That is also why a given mass of air tends to cool as it rises because it is also expanding in volume due to decreasing external pressure squeezing it together. Density is mass per unit volume.
re post by: Bill Illis says: November 29, 2011 at 4:40 am
Thanks for the explanation Bill.
Spector says:
November 30, 2011 at 1:52 am
“These pressures can only be measured from aircraft. Weather balloons are also aircraft. In general, air pressure decreases exponentially with increasing altitude because of decreasing density (thinning out) with increasing altitude. That is also why a given mass of air tends to cool as it rises because it is also expanding in volume due to decreasing external pressure squeezing it together. Density is mass per unit volume.”
;————————————————————————————–
Okay, thanks.
There was rumor NASA was developing differential radar to measure pressure.
Assuming the only forces acting on a parcel of air are the forces resulting from the gradient of the pressure and the gravitational field, then at mechanical equilibrium, the forces sum to zero and the solution the differential equation results in the pressure decreasing exponential with the height.
If the gravitational field were to vanish, then the pressure would be constant with height.