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Ocean Warming: Not As Simple As Headlines Say

Dr David Whitehouse, GWPF Science Editor

The bottom line of this paper is that according to the authors the world’s oceans (i.e. parts of them) have increased in temperature by less than 0.1 degrees C in 60 years.

It’s the usual story. It’s the beginning of the year and the statistics of the previous year are hurriedly collected to tell the story of the ongoing climate crisis.

First off, we have the oceans which, according to some, are living up to the apocalyptic narrative better than the atmosphere. The atmosphere is complicated, subjected to natural variabilities, that make the temperature increases open to too much interpretation. The oceans however are far more important than the air as they absorb most of the anthropogenic excess heat. Looking at the literature reveals no one knows just how much excess heat (created in the atmosphere) it mops up or indeed exactly how or where it does it. Some say it is 60% which is a bit on the low side, most say 90% or 93%. The real figure is unknown though it should be noted that a few percent error translates to a lot of energy, about the same amount that is causing all the concern.

On 14 January the Guardian had the headline, “Ocean temperatures hit record high as rate of heating accelerates.” The study that reached this conclusion was published in the journal Advances in Atmospheric Sciences.

It’s a badly written paper full of self-justifying statements and unwarranted assumptions that should have been stripped-out by the editor. Essentially there is only one new bit of information in the paper – the Ocean Heat Content (OHC) for 2019 as calculated by the Chinese Academy of Science using a newish technique that fills in places (and there are a lot of them) where there is no temperature data, so one should be careful analysing the output of their model. Curiously, the paper was submitted on 26 December, before 2019 was over. It was revised on 6 January and accepted three days later, perhaps that short time period explains the typos in the paper.

They find that the OHC for 2019 was (upper 2000m) 228 +/- 4 ZettaJoules above the 1981-2010 average and 25 +/- ZJ above 2018. I do wish people would stop using ZettaJoules. They are cumbersome and awkward. In my view all such measurements and calculations should be simpler and also expressed in terms of temperature increases and in energy increase per square metre for the whole earth’s surface and for the ocean surface. This way the data is so much easier to compare. It should also be mandatory to include error estimates. The data used in the paper is available but is obscure and hidden away.

The authors find, unlike many other studies, that there has been an almost perfect linear increase on OHC since about 1986. It is remarkable that the oceans have been able to do this. As one can see from their other figures the increase in OHC has not been uniform globally. The heating has been patchy, mainly the Arctic and the eastern seaboards of continents. How these warming regions, separated by vast areas that have not warmed much or even cooled, have maintained the coherence of a global linear trend of such precision is a wonder indeed!

The authors say in the paper, “With these newly available IAP data, a ranking of the warmest years since (the) 1950s is now possible.” Actually, it was possible last year and in the years before that. It’s another piece of unscientific hype that should have been taken out of this paper.

The bottom line of this paper is that according to the authors using this relatively new technique they have of replacing no temperature with synthetic data the world’s oceans (parts of them) have increased in temperature by less than 0.1 degrees C in 60 years.

As for the exquisite linear trend they find since 1986 compare this claim with recent data obtained solely by the Argo Array data set which has the benefit of much better statistical coherence. If you do, you will get a more realistic picture of what is actually happening.