The broad lack of differentiation prevent useful results
Posted: March 14, 2019
Sea surface data have fascinated science since long. Sea going vessels were requested to collect water temperature around the world frequently, often once on each watch. But what are they worth today if the method of measurements changed several times, and the type of ships and the sample taking seaman varied on a daily basis. There are many other variations, for example the sea surface conditions by wind and height of waves. While that inherits uncertainty, any attempt to adjust them unison will improve little if anything.
In addition, all corrections would be very unreliable if human activities at sea are not taken into account, indeed not even mentioned. These include the naval wars 100 and 80 years ago. One can only wonder that even serious scientists seem unable to take into account the highly different situation at sea during the Second World War, which has been discussed in two detailed essays 20 years ago.
Changes in instrumentation and data availability have caused time‐varying biases in estimates of global and regional average sea surface temperature. The size of the biases arising from these changes are estimated and their uncertainties evaluated. The estimated biases and their associated uncertainties are largest during the period immediately following the Second World War, reflecting the rapid and incompletely documented changes in shipping and data availability at the time. Adjustments have been applied to reduce these effects in gridded data sets of sea surface temperature and the results are presented as a set of interchangeable realizations. Uncertainties of estimated trends in global and regional average sea surface temperature due to bias adjustments since the Second World War are found to be larger than uncertainties arising from the choice of analysis technique, indicating that this is an important source of uncertainty in analyses of historical sea surface temperatures. Despite this, trends over the twentieth century remain qualitatively consistent-
To some surprise JJ Kennedy believes that better results can be achieved. He writes at about page 33 of the paper (extract):
“6. Remaining Issues
 The understanding of uncertainties associated with in situ SST measurements can be improved by increasing the number of observations stored in digital repositories such as ICOADS. The exact amount of undigitized data is unknown but some estimates suggest that the amount of undigitized data from before the Second World War is larger than the amount that has already been digitized (R. Allan, personal communication, 2011). As well as digitizing observations from log books, metadata are also being systematically scanned and stored online. Additional metadata can inform the assumptions made in estimating data biases and allow a more accurate assessment of the uncertainties. For a much more thorough background to these efforts, see Brohan et al. . Of particular interest is the period of the Second World War. It is not clear exactly how measurements recorded in the Met Logs of U.K. ships (as opposed to the deck logs) were made during this period.”
S. Fred Singer (see above) shows little sympathy how JJ Kennedy – and other researcher – handles the matter, saying amongst other things:
In merging them, we must note that buoy data are global, while bucket and inlet temperatures are (perforce) confined to (mostly commercial) shipping routes. Nor do we know the ocean depths that buckets sample; inlet depths depend on ship type and degree of loading. Disentangling this mess requires data details that are not available. About all we might demonstrate is the possibility of a distinct diurnal variation in the buoy temperatures.
A recent post in last November 2018 discussed “An ominous discovery? Sea Temperature or Climate? A dramatic climate shift after WWI still not understood” HERE where the matter is discussed as well, for example with regard to the 3,800 free-drifting profiling floats and in addition some sensors arrayed at depths in the North Atlantic.
The floats are a big achievement, but presumably less than a drop on a hot stone. The simplefact is that the ration between water volumes of the oceans versus atmosphere is 1000 to 1. That applies not only for the size and depth of the ocean, but also to the difference in global average temperatures; oceans about +4°C, the atmosphere about 13.7°C (56.7°F), respectively according NASA, the period 1951-1980, 14°C (57°F). Latter are collected by around 6’000 stations with many ten-thousand observations daily since the 20th Century, while available ocean data comprise only a very, very tiny fraction of those numbers. Whether it is possible to make an assertion about the warming of the entire oceans should be doubted. Here: https://1ocean-1climate.com/the-new-york-times-on-ocean-warming-jan-10-2019/