Buckets, Inlets, SST's and all that – part 1

There has been a lot of discussion lately about the accuracy of measuring Sea Surface Temperatures prompted by a new study from Phil Jones from the University of East Anglia and Director of UEA’s Climatic Research Unit. The measurement issue for sea surface temperatures that Dr. Jones is studying was recently showcased in an article in the UK Independent.

I’m going to present the article here first, and then we’ll talk about how sea surface temperatures have been measured, and what sorts of issues the changes between cloth buckets, metal buckets, and engine inlets actually entails.

At first glance, I see this issue raised by Phil Jones as not being well thought through, and ignoring the measurement environment actuality, instead focusing on the change in bucket types as being “absolute”. I think it has a lot of grey area, and a lot of potential errors that haven’t been considered. I’ll cover those in the next part, but for now please read the article and let me know what you think.

Case against climate change discredited by study

By Steve Connor, Science Editor

Thursday, 29 May 2008

A difference in the way British and American ships measured the temperature of the ocean during the 1940s may explain why the world appeared to undergo a period of sudden cooling immediately after the Second World War.

Scientists believe they can now explain an anomaly in the global temperature record for the twentieth century, which has been used by climate change skeptics to undermine the link between rising temperatures and increases in atmospheric carbon dioxide.

The record for sea-surface temperatures shows a sudden fall after 1945, which appeared to go against the general trend for rising global average temperatures during the past century.

Skeptics have argued it supports the idea that rising temperatures have more to do with increased solar activity – sunspots – than increasing levels of man-made carbon dioxide exacerbating the greenhouse effect.

However, an international team of scientists has investigated the raw data from the period. They found a sudden increase from 1945 onwards in the proportion of global measurements taken by British ships relative to American ships.

The scientists point out that the British measurements were taken by throwing canvas buckets over the side and hauling water up to the deck for temperatures to be measured by immersing a thermometer for several minutes, which would result in a slightly cooler record because of evaporation from the bucket.

The preferred American method was to take the temperature of the water sucked in by intake pipes to cool the ships’ engines. Those records would be slightly warmer than the actual temperature of the sea because of the heat from the ship, the scientists said.

Taking into account the difference in the way of measuring sea-surface temperatures, and the sudden increase in the proportion of British ships taking the measurements after the war, the result was an artificial lowering of the global average temperature by about 0.2C, said Professor Phil Jones of the University of East Anglia in Norwich.

“It occurred in the period of the 1940s when the number of observations of sea-surface temperature were markedly fewer than either before or after that period and most of the measurements were made by British and American ships. This made the apparent anomaly more pronounced,” Professor Jones said.

The study, published in the journal Nature, found that the global average temperatures in the late 1940s stayed roughly the same rather than falling. David Thompson of Colorado State University, the team’s leader, said a drop was, in effect, an artifact rather than a real observation.

“I was surprised to see the drop so clearly in the filtered data, and working in partnership with others, realized it couldn’t be natural,” Dr Thompson said.

Although the initial drop was significant, it did not last. By the 1960s, many other nations began taking ship-borne measurements of ocean temperature, minimizing the discrepancy.

Professor Jones said that the study lends support to the idea that a period of global cooling occurred later during the mid-twentieth century as a result of sulphate aerosols being released during the 1950s with the rise of industrial output. These sulphates tended to cut sunlight, counteracting global warming caused by rising carbon dioxide.

“This finding supports the sulphates argument, because it was bit hard to explain how they could cause the period of cooling from 1945, when industrial production was still relatively low,” Professor Jones said.

A similar problem could be occurring now with the move from ship-borne measurements to those from unmanned buoys, which tend to produce slightly lower records. This could explain why global average temperatures in recent years have leveled off.

FYI: According to the American Meteorological Society:

bucket thermometer—A water-temperature thermometer provided with an insulated container around the bulb.

It is lowered into the sea on a line until it has had time to reach the temperature of the surface water, then withdrawn and read. The insulated water surrounding the bulb preserves the water reading and is also available as a salinity sample.
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Retired Engineer
May 30, 2008 8:14 pm

I suspect that no matter what the real data shows, some ‘scientist’ will prove it is always getting warmer, anything to the contrary is in error and needs ‘adjustment’. That works for a while, but sooner or later, the data is so far removed from reality that no one believes it. The real question is how much damage will be done ‘solving’ the problem before everyone realizes the problem doesn’t exist.

May 30, 2008 8:53 pm

A similar problem could be occurring now with the move from ship-borne measurements to those from unmanned buoys, which tend to produce slightly lower records. This could explain why global average temperatures in recent years have leveled off.
Figures this would come up now for a reason. Its not like this problem wasn’t known (Climate Audit at http://www.climateaudit.org/?p=3116).

May 30, 2008 9:17 pm
May 30, 2008 9:17 pm

First of all this is major news that will open a full can of worms.
From several discussion I had, many people seems to believe that only the data from 1945 to 1965 need to be adjusted. They seem to believe that either the bucket stopped being use in the mid-60s or that by some miracle the bias between buckets and inlets was inexistent after the mid-60s.
Phil Jones seems to know something that others don’t, in pretending that it confirms the aerosol effect.
Some scientist that had to work with sea surface temp data aren’t to happy about these findings since it will undoubtedly render many paper obsolete and change many conclusion.
For sure data before 1941 won’t need to be re-adjusted since they already were. and the data from the last 10-20 years shouldn’t change that much either since the bucket were mainly phased out.
I’m not sure how the data will be handled but it will take some times there can be any agreement.
On the plus side the discovery of this error may force Jones to provide is data-code-method.

May 30, 2008 9:57 pm

I don’t see how this article makes any sense. When skeptics bring up the argument about mid-century cooling, it is to suggest that there are natural factors in play. The adjustment (dotted line) according to the graphic doesn’t change the mid-century trend; it merely gets rid off a sharp cooling trend (1942-1951) and a slightly less sharp warming trend (1951-1961) and replaces it with a mild cooling trend. This does not change the mid-century cooling trend, and it does not add any credibility to aerosol argument, as the writer claims.
It reads, “Professor Jones said that the study lends support to the idea that a period of global cooling occurred later during the mid-twentieth century as a result of sulphate aerosols being released during the 1950s with the rise of industrial output,” yet earlier in the article, the author seems to imply that the adjustment gets rid of the cooling period used by skeptics to refute AGW claims.
Steve McIntyre at Climate Audit has written about this issue before, and he has posted his own graph with adjustments done to the data. His graph shows no real cooling period, but a sustained, less steep warming period from 1950 to the present. This has important implications for relevance of aerosols, solar variation, and oceanic cycles to global temperature.

May 30, 2008 11:18 pm

Prof Jones makes this claim because the author of the article either believe that no adjustment is required after the mid-60s or that the adjustment won’t change anything after the mid-60s.
I don’t see how they will be able to justify only part of the data without being called about it.

May 30, 2008 11:46 pm

I can see 2 issues here.
The cooling after WWII at a time when CO2 were rapidly increasing was inconvenient for AGW theory. This lessens the problem and makes 20th warming look more like 20th century CO2 levels, i.e. the correlation will improve and hence a stronger causative argument made.
More importantly this paves the way for a bigger role for sulphates in AGW theory (and probably models as well).
The models have a serious problem because temperatures over the last 10 to 30 years (depending on your dataset) look nothing like what the models and AGW theory predict and as each new month’s data comes in the problem gets worse. And despite their brave face on the issue the Warmers are desperate for something that will explain away this problem.
A bigger role for sulphates will alow them to argue that AGW is being masked more than we thought by sulphate aerosols (they already argue that a substantial proportion of CO2 induced warming is being masked by sulphate aerosol cooling based on weak to non-existent evidence).
This would appear to be an attempt to get a bigger figleaf for the increasingly embarassing climate model predictions.

May 31, 2008 1:54 am

For those of us who believe that natural oscillations in ocean temperatures, in addition to changes in solar irradiance, drive global temperature, these corrections reinforce, they don’t discredit, our position. The correction to the global temperature anomaly curve that seems most likely to be made, right or wrong, is the one based on the claims of Jones and others, the one represented in the curve above. This actually makes it easier to match the global temperature anomaly curve and trend with solar, volcanic aerosols, AMO, ENSO, and the PDO.
We’ll just have to see how the SST corrections impact not only global temperature, but also how they change the influences of AMO, ENSO, and the PDO.

May 31, 2008 2:01 am

Looking at that global temp chart it looks like they are missing a recorded period of unprecedented Arctic sea ice melt between 1900 and 1929, and another big warming period in the 1930s. They have bigger problems with their data then can be explained with any damn bucket.

D. Quist
May 31, 2008 2:05 am

Water has a tremendous thermal inertia. The temperature of a bucket of water is not going to rise, or drop, 0.3C in a few minutes. Perhaps some person with personal experience could tell me otherwise. A bucket of water say at 55F is brought up onto the deck of a steel ship. The air temperature is say 85F (Not sure that is possible in the middle of an ocean that is at 55F). HOW FAST will the temperature rise in a bucket of water in these conditions, (cloth or otherwise) in say 5 minutes?
Now there is no way that evaporative cooling is going to have any effect. A 0.3C in five minutes, on a bucket of water, NO WAY!
OR, maybe I am ignorant. How much water is in one of these buckets, a teaspoon or Five Gallons?
Could someone provide numbers please, facts, tables, proven results! Has anyone ever taken temperature, At the Same TIME, from a bucket and an engine inlet, etc. to compare the difference? Come on folks! This ain’t that complicated.
If you put a thermometer in the middle of a parking lot you are going to get global warming. If you change from bucket to engine intake on a ship you might have a problem. These guys might have a valid point.
It seems that in this case that temperature can be measured with substantial confidence, using each method, bucket and enine inlet, an accurate table of temperature change can be produced for various conditions.
P.S. Anthony this is no different then your project. What happens if the bucket is brough up in the shade. What if it is done at 6:00AM. What if it is a 1940 navy ship with teak deck? Modern ships are all steel, no teak. If the crewman who is sent out to do it always does it in lee? Then you don’t have much eveporative cooling.
Alrighty then, we got this one all figure out?

May 31, 2008 3:25 am

Cooling trend from1942-1951,
I am 67 years old and live in the Trent valley UK. Until Thatcher closed the coal mines and coal power stations went out of favour, there were many coal fired power stations situated within this valley. The reason for this was the abundance of cooling water and nearby cheap coal.
I was informed that because of the number of these power stations the temperature within the valley was a degree or two above the average.
As I recall, in the late 1940`s and early 1950`s I would as a child wake up in winter and try to scape the thick ice off the inside my bedroom window, I would walk to school passing hedging weighted down by the massive frosts, I was taken by my parents to our local park at Nottingham University, to skate, toboggan, and slide on the lake. I would make ice slides in the school playground and slide on the frozen river coming home. This was in the Trent Valley which was a degree or two above the average, it has not happened again since that time.
Of cause there was a significant dip in temperature during that period, certainly in the UK. Are they trying once more to rewrite history, are the frost fairs a figment of the artist`s imagination.

kum dollison
May 31, 2008 7:10 am

None of this really matters. If, in 2010, it’s as cold, or colder, than it is now the “Solar” team wins. IF, it’s warmer than 1998 the CO2 guys will win. If it’s somewhere in between the argument will go on.

Pamela Gray
May 31, 2008 7:33 am

All this knat’s ass hair splitting is beginning to sound laughable. I am also beginning to be less worried about preparations for food production in the face of cold, short growing seasons. Vineyard owners will be looking for ways to produce something, since their harvest in 2007 was 50% of their average. Can’t make money doing that. If it don’t produce two to three years in a row, it won’t be planted again with that same crop. Wheat prices are also rising to the extent that CRP payments on idle land cannot compete with planting wheat. I am also seeing what was once pasture being turned back into planting acreage. Short season cold crops like peas will be coming back to the fertile plains in northeast Oregon because the crop will be tall enough to harvest. In the mid-70’s many acres of peas had to plowed under because the harvest machines could not get low enough to cut the crop. This season would have been perfect for peas and the drought resistant wheat that is growing around here is so thick you can’t see the soil unless you make a good effort to part the young plants with your hands. I believe market forces will rule the day and leave nit-picking scientists holding an empty bucket.

Mike from Canmore
May 31, 2008 7:55 am

Excuse my ignorance but I don’t understand why ocean water temps. come into play when the charted temp. is air temp. measurements Land based weather stations are measuring air temp. They aren’t pulling up buckets of water and measuring the water temp. If one is trying to somehow incorporate the air temp. of 2/3s of the earth in the equation, wouldn’t one want to measure the air temp. over 2/3s of the earth? If one is going to measure buckets of water, wouldn’t that imply some “adjustments” must be made. It seems like an apples and oranges thing. No sarcasm implied. Honest question and would really appreciate your comments.

Michael Ronayne
May 31, 2008 9:46 am

The problem with Dr. Jones’ leaky bucket theory is that the temperature record, using only the surface stations, shows exactly the same drop in temperatures after 1945. Directly from the House of Hansen you can compare the graphics for the land surface stations and the combined land-ocean index.
Global Annual Mean Surface Air Temperature Change
http://data.giss.nasa.gov/gistemp/graphs/ (scroll down)
John Daly reported on this subject and used some GISS graphics which are no longer available at the House of Hansen.
The ‘Surface Record’
If the temperatures continue to drop I expect even more creative and entertaining theories. My personal favorite was that air pollution after 1945 cause the decline in temperature.

May 31, 2008 9:50 am

“I was surprised to see the drop so clearly in the filtered data, and working in partnership with others, realized it couldn’t be natural,” Dr Thompson said.”
For Thompson to make such claim with a straight face while not attributing the “discovery” to Steve McInctyre who wrote about this inconsistency several times more two years ago is clearly a case of scientific misconduct. It has a name : plagiarism.
Those guys have no shame.

May 31, 2008 9:52 am

Mike from Canmore, as a practical matter we can’t measure temperature 5 feet above the ocean surface at the same location over many years the way we do on land.
Otherwise, you have a point and in the climate debate every measurement is a proxy for some other value and the precision of these proxies is uncertain to say the least – ref Mann and Bristlecone Pines.

George Tobin
May 31, 2008 9:53 am

The temperature chart is curious. Were all the years from 1920 to 1940 below average? I recall something about hot weather, dust bowl, big economic flap etc. somewhere in that period.
The only explanation for this graph is that the those canvas buckets must have been lifted out of the water using a hockey stick.

May 31, 2008 9:56 am

How is the case discredited? I still see a 35 year cooling trend from 1940-1975 in the face of rising CO2 emissions with no observable evidence that lower atmospheric aerosols cause cooling at all (see warming trends for the last 20 years or so in aerosol laden China for instance).

Jon Jewett
May 31, 2008 10:30 am

I am a retired merchant marine engineer. I made my living on merchant ships from 1966 to 1999, when I retired as Chief Engineer of a 32,000 SHP steam turbine powered container ship.
A ship moves through the water at between 12 knots and 22 knots. (Twelve knots for an old Liberty Ship from WWII, 22 knots fairly representative of new ships.) At even 12 knots, the speed is fast enough to cause turbulent flow of the sea water and thereby prevent a “warm” layer forming along the ship. In addition, very little of the ship is a significant heat source; only the area in way of the machinery spaces. Most of the ship is thermally inert cargo space that may be warmer or colder than the sea temperature. The main cooling water pump (Main Circulator) takes suction through the hull at a depth of 15 feet to 60 feet (depending on the ship) below the surface of the water. In addition, a Main Circulator will pump up to several thousand gallons per minute.
In short, the concept that the water would be heated by a measurable amount is far fetched at best. The statement indicates that assumptions were made about the measurement process and there was no meaningful investigation before these opinions were voiced.
Actually, there is cause for concern in using these numbers. Typically, either alcohol type bulb thermometers or bimetallic type thermometers were used. They were calibrated at the factory before they were installed, but never after that as long as the readings were “close enough”. It was not until the late ‘60s that thermo-electronic (e.g. RTD and Thermister) methods started to enter the fleet. It is to be expected that, particularly with the older readings, each one may be on the order of up to 10 degrees off, with a random distribution.
Steamboat Jack

Robert Wood
May 31, 2008 11:00 am

Problems with the data, then adjust it!
It looks more and more like the only trustworthy data are the satellite and Argos data.

Vincent Gray
May 31, 2008 1:17 pm

As I point out in my paper at
The Jones record is hopelessly biased, and the fall in temperature after 1940 is well recorded by many other records ON LAND, such as the corrected recorrds for the USA and China, for the Arctic (e.g. Iceland) and many other reliable local records.
How can they possibly rescue this flawed dataset?

May 31, 2008 1:26 pm

To reinforce my statements above, it’s relatively easy now to recreate the global temperature anomaly curve using natural influences. Once they make the corrections, it should get easier.
A Skeptics Recipe for Creating the Global Temperature Anomaly Curve
Separate the ACRIM Phenomenological Solar Signal (PSS) from the Scafetta and West illustration:
Chill with the effects of the explosive volcanic eruptions:
Scramble the curve with the influence of El Nino and La Nina episodes:
Blend in the AMO:
Season with the PDO:
Then compare to Global Temperature Anomaly:
The proportions are discussed in detail here:

Chance Metz
May 31, 2008 5:42 pm

Well someone have the time to in the world to do all this adjusting of the temperature curve.

May 31, 2008 7:15 pm

Weren’t the AGW computer models simulating the old curve with their simulated aerosol layers? So if reality is different than the old curve, how does that make the computer models seem better? It just leaves the computer model simulations digging themselves a colder hole in the dirt ocean than before. The mystical computer calculations are again shown to be erroneous.

Mike from Canmore
May 31, 2008 9:23 pm

Thanks for answering. So, I’m not reading that wrong. They are actually taking water temps and using it as a proxie for air temp.
That being said, did they measure water temp. exactly 5 ft. below the water at the same location over many years? Seems to me if air temp. was taken then “proxied back, (if that’s a phrase), that would have better attributes then water temp. At least then one could time, date, location, etc. stamp the measurement and adjust accordingly. If one were trying to measure the ocean heat content, measuring water temps would make sense to me. But you can get such rapid changes in air temp. and for intent and purpose zero change in water temp. over the relatively short term, to use water temp. as a proxie to air temp. just sounds “fishy” to me.
Again, thanks for answering.

May 31, 2008 10:07 pm

I don’t think there is any way that ships could have surveyed water temperatures over a large enough extent of the oceans over the years to have a viable plot of water temperature vs. time. I wonder if they are examining the calibration data for those devices that made the readings?

Jack Simmons
June 1, 2008 1:29 am

Evidently, climate change means not only changes in the future, but changes in the past.
Eppure, si rinfresca

June 1, 2008 7:24 am

The key point in all this is that the “scientists” made a wild-assed guess without any factual support in adjusting the data. They just made it up! Why in the world would anyone put any credence in the work of such people? If this is what passes for real science, all scientists are in for a serious collision with reality. Voters won’t pay for this kind of garbage forever. If making up wild-ass guesses isn’t standard procedure for scientists, then the real scientists better start actively getting in front of exposing the frauds. Otherwise, they are going to get tarred with the same brush when the backlash comes.

James Bailey
June 1, 2008 8:06 am

Sea water and the water vapor in the adjacent air is already in equilibrium. I sincerely doubt that they have taken the water high enough that the bucket needed to evaporate to reequilibrate.
But, water temperatures are mild compared to air temperatures. So as they wait for a reading, the water should be cooling in winter or heating in the summer. In the latter case, evaporation is a secondary response, slowing down the heating.
These people seem to have invented a new form of refrigeration. Take a large body of water, pull up a bucket of it, and the water in the bucket magically cools itself.

Michael Ronayne
June 1, 2008 8:14 am

There is one other graphic at the House of Hansen which is noteworthy. This is the temperature history of the (lower 48) United States. This was a favorite of John Daily because the United Sates had the best network of surface stations on the planet, as made as they are.
As reported at Climate Audit and this website, Dr. Hansen and gone to great lengths to make “homogeneity adjustment” to this data so that it would yield the desired results. I am going to be very interested to see what the data for 2008 shows on this graphic.

June 1, 2008 12:41 pm

Steamboat Jack:
During his brief stint in the USN back in the ’80’s my friend remarked how darn cold the hull was even down next to the boilers.
This publish-or-perish data half-bakery looks awfully desperate to me. Anything to clean up unexplained anomalies, it’s like rectifying the Ptolemaic system with epicycles. That Newton was just as guilty of cramming epicycles into his celestial model just goes to demonstrate how tempting such chicanery is. Sometimes some phenomena are best left unexplained until better science can address current perturbations. And some data are best left as mysteries never to be solved.

June 1, 2008 1:11 pm

Bob Tisdale,
Bob, this is excellent work. http://bobtisdale.blogspot.com/2008/05/will-corrections-to-global-temperature.html
Could you also show the trend lines without the PDO scaling factor?
It might be a 2nd project, but if the point of this exercise is in seeing what trend line is left after all the noise is canceled from the various other natural sources, it’d lend to a hierarchical linear regression that’d leave us with the CO2 signal. Other efforts I’ve seen leave a very marginal effect (Jan Janssens has a similar effort on his website).
Solar forcing would have increased ocean temperatures, el Nino & AMO+ magnitudes over the past century until about 1990-1995, when the sun started dimming again. I would assume then that PDO & AMO magnitudes could be phase adjusted. Perhaps it’s feasible to, in a stepped fashion, de-noise the solar impact on the troposphere, PDO & AMO which in turn would provide their own subtractive phase adjustments against the general trend. PDO & AMO perturbations put back into the solar column would leave CO2 or other factors in the PDO & AMO column, etc.
I’m guessing the remaining trend line would leave noise from two remaining factors: Aerosols (which in fact cause a net warming — see Ramanathan & Carmichael, 2008), soot deposition in the Arctic (19 percent of all AGW since 1850) and CO2 (with its natural effect Temperature = Temperature0 + ln(1 + 1.2x + 0.005x^2 + 0.0000014x^3) ).
I have *yet* to see a warmist explicate the contributory phase adjustments on the various climate factors.
It may also be notable that the ionosphere contributes terawatts of energy into the global environment, potentially stronger at the poles.

Leon Brozyna
June 1, 2008 3:31 pm

This looks too much like, “the data doesn’t fit the model, therefore, the data must be wrong.” Now, I’ll grant you that the data might be flawed, but in light of recently observed repeated tweaking of data that doesn’t conform to models, this latest episode looks suspicious. An honest scientist would be hitting the models as well to find their flaws. And while the above graph shows some smoothing, it still shows that some cooling happened during that period up to the mid-70’s.
The models might attain a degree of credibility if they could forecast such long-lived phenomena as the decadel oscillations in the Atlantic, Arctic, and Pacific Oceans. They must also show the impact of solar activity on climate and not make the unwarranted assumption that because we’ve experienced a certain similar though varying level of solar activity over past century, that such activity will continue into the future. This assumption is sure to haunt the modelers in coming decades as solar activity declines to levels not seen in over a century.

Chance Metz
June 1, 2008 4:55 pm

Warming somehow becuase cooler is jsut wrong to even suggest let alone put on a official AGW graph.

June 2, 2008 7:41 am

I’m getting confused here. The modelers have spent the last decade telling us how great the match between model output and historic temperature trends have been. Now we see a substantial change to about 20 years of the historic record, and we are being told that this change dramatically improves the match between the historic record and the output of the models.
If the match was already great, how come there was need of a substantial improvement?

June 11, 2008 1:32 pm

These people seem to have invented a new form of refrigeration. Take a large body of water, pull up a bucket of it, and the water in the bucket magically cools itself.
They’re canvas buckets. Here in Australia we used to put water in a canvas bag and hang it in the breeze. It would cool very rapidly. The stronger the wind, the quicker the cool. If there was a breeze at sea, or if the ship was traveling (I read that they often were for these bucket hauls – hard on the arms!), then the water in the canvas bucket would start cooling the moment it broke the surface. How fast I don’t know, but I know that water in canvas cools pretty damned quick.
I see from the graph that the peak difference is 0.2C. They kept the thermometer in for three minutes – that’s after hauling the bucket out of the water, so let’s say the bucket was getting sea breeze for 3 and a half minutes. Doesn’t sound too far fetched to me that this resulted in a measurable drop. How much capacity did they have?
The article’s pretty vague on the terminology. ‘Global temperature’? Is that ocean temps, land and ocean, surface temps?
It’s rarely useful to haggle over the science in a newspaper article.

June 11, 2008 1:51 pm

Hey, my memory works!
The contraption there at wikipedia is pretty fancy. The ones I’ve seen are just the canvas bag hanging in the shade. It would cool to pretty chilly even on scorching days if there was a bit of a breeze. First time I saw one and had a drink from it, it did seem like magic.
If you have a canvas bag of the right weave, a thermomoeter and a low spinning fan, you could do your own experiment right now. Take the temperature of the water (whatever volume they used to pull up the side of the boat) from a solid container, transfer to canvas bag, turn on the fan (move it to a distance you think would be an average wind-speed for a boat at sea, allowing for traveling speed etc), stick the thermometer back in for three and a half minutes and see if there’s a difference. You’d want to approximate the shape and size of the canvas bucket, too. If it’s thin, the water cools more quickly.

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