Historical Sea Surface Temperature Adjustments/Corrections aka "The Bucket Model"…

Image Credit: Bob Tisdale – bobtisdale.wordpress.com

By WUWT Regular Just The Facts

The recent Adjustments/Corrections to the HadCRUT4 and CRUTEM4 Temperature Data Sets by the Met Office Hadley Centre and Climatic Research Unit got me thinking about the cumulative impact of Adjustments/Corrections on our temperature records. Bob Tisdale then triggered the first vein of this analysis when he recently produced and provided the graph above, which compares the ICOADS (International Comprehensive Ocean-Atmosphere Data Set) v2.5 data set to HadSST3, HADISST and ERSST.v3b. ICOADS is the original unadulterated Sea Surface Temperature record. HadSST3, HADISST and ERSST.v3b, all include adjusted/corrected ICOADS data, e.g.:

[Note: Bold and non-link underlines below are mine. I am testing out a new three speed review approach, i.e. if you really want to know it, read it all, if you want an overview, read the underlines and non italics, if you want the key concepts, read the bold and non italics. Please let me know in comments if this approach works for you.]

HadSST3 The SST data are taken from version 2.5 of the International Comprehensive Ocean-Atmosphere Data Set, ICOADS (external web page), from 1850 to 2006 and on GTS observations from 2007 onwards. HadSST3 is produced (a slightly more detailed description) by taking in-situ measurements of SST from ships and buoys, rejecting measurements that fail quality checks, converting the measurements to anomalies by subtracting climatological values from the measurements, and calculating a robust average of the resulting anomalies on a 5° by 5° degree monthly grid. After gridding the anomalies, bias adjustments are applied to reduce the effects of spurious trends caused by changes in SST measuring practices. The uncertainties due to under-sampling and measurement error have been calculated for the gridded monthly data as have the uncertainties on the bias adjustments following the procedures described in the paper.

The HadSST3 page references this paper “Improved Analyses of Changes and Uncertainties in Sea Surface Temperature Measured In Situ since the Mid-Nineteenth Century: The HadSST2 Dataset“, Rayner, et al., 2005, as the basis for their adjustments/corrections. It states within that:

a. Bias correction and its uncertainties Seawater has been sampled for temperature measurement on board ship by various different means at different times. This change from using insulated (wooden) to uninsulated (canvas) to partly insulated (rubber) buckets, engine room intakes, and hull sensors, along with changes in ships speeds, has introduced changing relative biases into the database. Folland and Parker (1995) developed corrections to be applied to SST data between 1856 and 1941 to ameliorate the effect of these changes and to bring the older data into line with data from the modern mix of measurement methods. For details of the development of these corrections, the reader is referred to Folland and Parker (1995).

Here’s Parker, Folland, M. Jackson (1995) paper MARINE SURFACE TEMPERATURE: OBSERVED VARIATIONS AND DATA REQUIREMENTS Here are some of the adjustments/corrections detailed within:

“Overall global warming in SST between the 1860s and the 1970s is about 0.3 °C greater in the present analysis than in Folland et al. (1984), mainly owing toreduced early corrections applicable under the assumption of the predominant use of wooden buckets (Section 3).”

“The largest, positive corrections are in early winter (December) over the Gulf Stream and the Kuroshio, where warm water, cold dry air, and strong winds cause rapid evaporative heat loss from the buckets. The corrections approach 1 °C by 1940 in these regions in early winter. Corrections are also large (around 0.4 °C to 0.5 °C by 1940) in all seasons in the tropics because of the high rate of evaporation when SST is high. Some negative corrections are made in mid latitudes in summer, mainly where the mean air temperature around the bucket exceeds the mean SST.”

Here’s their Figure 7, which shows the impact of their adjustments/corrections.

“How do we know that these corrections are trustworthy? The agreement of SST anomalies with largely independently corrected NMAT anomalies (Section 7 and Figure 7) is the strongest support to the results, and suggests that the impacts of future refinements and reduction of uncertainties in this area will be small.”

So who do you think provided the “largely independently corrected NMAT” SST anomalies, which are “the strongest support to the results”? Wait for it…

“Folland et al. (1984) applied corrections to NMAT to compensate for the historical increases of the average height of ship’s decks. These rose from about 6 m before 1890 to 15 m by the 1930s and 17 m by the 1980s. The corrections, based on surface layer similarity theory, removed a spurious cooling of about 0.2 °C between the late nineteenth century and 1980. On the other hand, Jones et al. (1986) used anomalies (not actual values) of regional, mainly coastal, land surface air temperature to adjust anomalies of nearby MAT. This was possible because anomalies of MAT and nearby ‘coastal’ land surface air temperature are found to be similar in recent data over periods as long as a decade, even though the absolute values differ considerably. However, because Jones et al. (1986) used COADS summaries, they were unable to separate NMAT from day MAT which are affected by historically varying, on-deck solar heating: their corrections therefore differed from those of Folland et al. (1984). In both these early studies, about 0.5 °C was subtracted from MAT for 1942-5, a period of non-standard measurement practices owing to war. “

Yes, that Jones et al. (1986) reference is Phil Jones, and Tom Wigley too, at the Climatic Research Unit (CRU), University of East Anglia (UEA). And it turns out that Rayner, Folland and Parker all worked at the Hadley Centre, Met Office.

This 1992 Jones and Wigley paper “Corrections to Pre-1941 SST Measurements for Studies of Long-Term Changes in SSTs” appears to be a seminal work in the development of Sea Surface Temperature record adjustments/corrections:

Many factors can influence a sea surface temperature reading (Barnett, 1985; Jones et al., 1986; Bottomley et al., 1990; Jones et al., 1991). Some of these introduce random errors while others result in systematic, non- cancelling errors. The most important factor is the method of collecting the sample, with the two basic methods being to haul a sample on deck with a bucket, or to measure the temperature of the intake water used for engine cooling. Here, we are concerned with bucket measurements. These are affected by the kind of bucket used, the exposure of and physical conditions surrounding the bucket, how long the bucket was left before reading the thermometer, and ship speed.

In COADS we do not have detailed information concerning the methods of measurement, nor any indication of what method was used for the individual readings that make up the data. There is,nevertheless, strong evidence that readings before 1940 were predominantly bucket measurements, while those since 1945 were predominantly intake measurements (Jones et al., 1986). Furthermore, it is likely that the major difference between the data for these two periods is the non-climatic bias due to the evaporative cooling of the canvas bucket, an effect which would clearly cause pre-1940 data to be cooler than post-1945 data (Jones et al., 1991).

In order to derive correction factors for the bucket-derived temperatures, we have modified the model developed by Folland and Hsiung, 1987 and Bottomley et al., 1990, to estimate the cooling of an uninsulated canvas bucket. The main difference between our work and that of Folland and Hsiung (1987) is that we have solved the governing equations analytically. This makes application of the model less demanding computationally, and it allows us to perform a variety of analyses.

2. The bucket model

If you have not already, you really should take a look at Section 2. “The Bucket Model” within Jones and Wigley’s 1992 paper, as it is a classic work in gibberish…

Continuing…

4. Correcting SSTs using the bucket approach

4.1 Optimum exposure time

For 1905-40, SSTs may be corrected using the evaporating bucket model. Although average ship speed probably varied over this period, within the range of likely values ship speed does not noticeably affect the implied exposure time. We have used a ship speed of 7ms-1. Wind speeds of 60% of the anemometer speed produce slightly better results than the 40% reduction case, and lead to slightly lower optimum exposure times (by less than 1 minute on average) so we have used this value. As the most likely exposure time lies in the range 3-6 minutes, we use 4 1/2 minutes in making final corrections.”

“4.2 The final correction factors

Final correction factors depend on the location, month and year. These variations are summarized in Figures 3 to 5. Correction factors vary slightly from year to year depending on coverage changes. Figure 3 shows mean correction factors for the Northern Hemisphere. Southern Hemisphere mean corrections are shown in Figure 4. The transition from small corrections in the early decades to larger corrections after 1905 is due to the change from wooden (i.e., better insulated and assumed to require no correction) to un-insulated buckets. Correction factors are largest in the winter half year. Northern Hemisphere corrections show slightly larger season-to-season variations. Figure 5 shows how the “winter” (JFM) and “summer” (JAS) – using Northern Hemisphere seasonal labels – corrections vary with latitude. Correction factors are lower in higher latitudes in general, particularly in the 45-75°N band where the “summer” corrections are near zero.”

It appears that the Team that brought us Climategate, was hard at work adjusting/correcting the Sea Surface Temperature record back in the 80s and 90s…

Here Jones and Briffa team up to summarize the purported basis of the Sea Surface Temperature record adjustments/corrections in their paper, “Global Surface Air Temperature Variations During the Twentieth Century: Part 1, Spatial, Temporal and Seasonal Details“, P. D. Jones and K. R. Briffa, 1992.

“Problems with the homogeneity of sea surface temperature (SST) data arise due to differences in the method of sampling the sea water. Before the second world war the sea water was collected in an uninsulated canvas bucket. There was a delay of a few minutes between sampling and measuring the temperature. During this time the water in the bucket generally cooled slightly by evaporative means. Since the second world War most readings have been made in the intake pipes through which sea water is taken onboard ships to cool the engines. This change in measurement technique was quite abrupt at around 1941, although there are still significant numbers of bucket measurements (using plastic and thus better insulated buckets) made today and some intake measurements were made prior to the second world war.

Comparative studies of the two methods indicate that bucket temperatures are cooler by 0.3-0.7″C (James and Fox, 1972). Correcting the SST data for this measurement change may seem, at first, seem an intractable problem. Folland and Parker (1990; 1991) of the UK Meteorological Office, how- ever, have developed a method for correcting the canvas bucket measurements based on physical principles related to the causes of the cooling. The cooling depends on the prevailing meteorological conditions, and so varies according to the time of year and location. Although the cooling is therefore a day-to-day phenomenon, the various influences are basically linear, so cooling amounts can be calculated on a monthly basis. The main free parameter is the elapsed time between sampling and reading. This is generally unknown and must be estimated from the data. The primary assumption in this estimation is that there have been no major changes in the seasonal cycle of SSTs over the period of record. Since the amount of evaporative cooling has a strong seasonal cycle in many parts of the world, an optimum exposure time can be chosen; namely that which minimizes the residual seasonal cycle in the corrected data.As a check on the validity of the method, the implied optimum exposure time turns out to be quite consistent spatially (see Jones and Wigley, 1990; Jones et al., 1991 for more details).

The major problem with the technique is that it is not known with any certainty what types of buckets were used to take measurements during the nineteenth century. Assuming canvas buckets rather than wooden buckets (which are better insulated) leads to corrections which infer SSTs warmer than land temperatures by about 0.2″C. The discrepancy almost disappears if wooden buckets are assumed. Although there is documentary evidence to support wooden bucket use during the mid-nineteenth century, considerable doubt remains about the transition from wooden to canvas buckets. The seasonal-cycle elimination method is not precise enough to choose between the two possibilities. The corrections used here have been derived using the wooden bucket assumption in the nineteenth century (see Jones et al., 1991 for details).

“The major problem with the technique” and “The Bucket Model” are that they rely upon an array of assumptions and estimations, which are based on very limited empirical data, and were made by people like Phil Jones and Tom Wigley, who have apparent biases, and appear to have been working the propagate the Catastrophic Anthropogenic Global Warming narrative since the early eighties. It is interesting to note that the Jones et al. papers on Sea Surface temperature adjustments/corrections do not appear listed within the otherwise quite encompassing collection of Jones’ work on the UEA website.

Steve McIntyre has written extensively about bucket adjustments starting back in 2005, i.e. Changing Adjustments to 19th Century SST;

You may recognize Folland as a major IPCC author (Folland et al. [2001] is sometimes the citation). SST sampling is not homogeneous – it changed from buckets to engine inlets – engine inlet temperature ran a little hotter. Both canvas and wooden buckets appear to have been used. There are millions of SST measurements and how the measurement was done is not known for most measurements (as far as I can tell.) There are two main adjustments in Folland et al. The first is a one-time adjustment for from buckets to engine inlets in December 1941. This is premised on a comparison between the “corrected” NMAT temperature [ I haven’t checked what these “corrections” are] and the uncorrected SST temperatures.

Buckets and Engines, The Team and Pearl Harbor, Bucket Adjustments: More Bilge from RealClimate, Rasmus, the Chevalier and Bucket Adjustments, Did Canada switch from Engine Inlets in 1926 Back to Buckets?;

CA readers are aware that I discussed bucket adjustments on a number of occasions long before Thompson et al 2008, in particular, questioning the absurd IPCC assumption that all SST measurements switched from buckets to engine inlet on the day after Pearl Harbour. In March 2007, a year before Thompson et al 2007, in light of new historical information bucket usage, I provided a scoping estimate of the potential impact of a different changeover scenario, based on then-just-published Kent et al 2007. The direction of the impact is precisely the same as that shown in the present HadCRU estimates over 4 years later. The difference between the two appears to be that the present HadCRU estimate assumes that bucket changeover impact has ended by 1970, while, in my 2007 post (based on Kent’s evidence of widespread bucket usage in the 1970s), I presumed that the changeover continued until the 1990s.”

and HadSST3;

A new HadSST3 version has been recently published. It starts the process of unwinding Folland’s erroneous Pearl Harbour bucket adjustment, an adjustment that has been embedded in HadSST for nearly 20 years.

Folland’s erroneous adjustment had been originally criticized at CA in 2005 here and further discussed at length in March 2007 at CA here, a post in which I observed that no climate scientist had made any attempt to validate Folland’s bizarre adjustment and that correcting Folland’s error (through a more gradual and later changeover to engine inlets than the worldwide overnight change that Folland had postulated after Pearl Harbour) would have the effect of increasing SST in the 1950s, in turn, potentially eliminating or substantially mitigating the downturn in the 1950s that was problematic for modelers.]

However, not until Thompson et al 2008 (submitted Jan 2008; published May 2008) was the problem with the Folland adjustment clearly acknowledged by the “community”. The importance of Thompson et al in resolving the problems arising from the Folland adjustment were credited by Susan Solomon and Phil Jones in the commentary accompanying the Nature article.) Both lead author David Thompson and co-author Mike Wallace, though very prominent climate scientists, had negligible (or no) publishing history on the topic; as one commenter at James Annan’s blog put it, they came out of “left field”. Thompson was an ozone specialist. The other co-authors, John Kennedy of the Hadley Center and Phil Jones of CRU, were, of course, actively involved in the field.

Now over three years later, in a new SST edition (HadSST3), the Hadley Center has accepted and implemented Thompson et al’s criticism of Folland’s Pearl Harbour adjustment. Instead of implementing an overnight changeover to engine inlets in December 1941 as before, the changeover is now phased in through the mid-1970s. This results in changes to SSTs between 1941 and ~1975.

However, Steve does not appear to have dug too far into the pre-1945 adjustment/correction highlighted by Bob Tisdale’s graph.

One piece of this puzzle I can’t seem to find is the oft cited Bottomley et al., i.e.: Bottomley, M., C. K. Folland, J. Hsiung, R. E. Newell, and D. E. Parker, 1990: Global Ocean Surface Temperature Atlas. MIT Press, 20 pp. plus 313 plates. According to the Global Ocean Surface Temperature Atlas GOSTA:

This is the January 1993 version of the Global Ocean Surface Temperature Atlas (GOSTA) (Bottomley et al., 1990) referred to as ATLAS7 or MOHSST5. The data in this atlas are a compilation of marine observations from the United Kingdom Meteorological Office Main Marine Data Bank with some additional data from the US Fleet Numerical Oceanography Center. The Atlas includes the climatology of sea surface temperature (SST) and the difference between marine nighttime air temperature (NMAT) and SST. These climatologies are based on data collected between 1951 and 1980. Also included are SST and NMAT monthly anomalies from 1856 to 1991. The data were corrected to remove what are believed to be observational biases due to changes in instrumentation. These correction are based on scientific research summarized in the introduction to the hard-copy version of GOSTA (Bottomley et al., 1990). All data are presented on a 5 by 5 degree grid wherever data existed. The climatology of SST can be made available on a 1 by 1 degree grid.

The quality of marine observations is thoroughly discussed in the hard copy volume of GOSTA as well as in the references therein. The user should note that the data were collected using a variety of instruments and observational procedures aboard vessels of different shapes and dimensions.

Here is the GOSTA data, however I would like to see the “scientific research summarized in the introduction to the hard-copy version of GOSTA (Bottomley et al., 1990).” to understands what those adjustments/corrections are based on, but even Google Scholar comes up dry.

If anyone can find an electronic copy of Bottomley et al., 1990 and/or can  offer additional information on the adjustments/corrections made to the to the Sea Surface record, please post them in comments.