Ocean Warming: Inadequate Data, Unknown Errors

  • Date: 15/01/19
  • Dr David Whitehouse, GWPF Science Editor

The oceans are warming, they have to be. If they were not then climate science would be in trouble. If ocean warming is not accelerating then climate science is also in trouble.

The warming of the oceans is one of the key topics in climate change. The Earth’s climate system is responding to an energy imbalance. Any positive imbalance in the world’s energy budget is bound to show up in the oceans as a rise in temperature because the source of the excess energy – heat-trapping greenhouse gases in the atmosphere – overlies much more ocean than land.

Reading some recent papers on ocean warming you might be forgiven for thinking they are behaving as predicted by some, warming more than expected, possibly with the warming accelerating. It has been said that we understand the oceans. For me this is premature. As we look ever closer at the oceans we are seeing more of what we don’t understand.

One such paper is replete with encouraging words to support their stance in the face of difficulties expressed elsewhere but unmentioned in the paper. The data “resemble models,” and “models reliably predict,” even, it is becoming “increasingly clear.”

That the oceans are warming is a conclusion of over a century of observations made in a variety of ways and connecting together these disparate datasets is difficult. Temperature measurements have been made from a variety of probes whose characteristics changed over time, or by different types of water inlets in ships, or by buckets and thermometers. They all give different results and have all been analysed and reanalysed and adjusted again and again and will certainly continue to do so in the future. Once their was a bump in ocean temperature during the 1940s, then it went away as it was an instrumental effect.

The only way around this problem is to consider a more coherent dataset – the Argo array of 6,000 or so buoys that started being distributed in 2006. The problem with that empirical data is that it is not yet really long enough, and what we have doesn’t agree with the data obtained by other means. The inhomogeneity of the data before the Argo array is a major problem, and the jump seen in Ocean Heat Content (OHC) with the introduction of the Argo array is another.

Measuring Ocean Heat Content is a subject struggling with inadequate data. It involves measuring the temperature of vast oceans (indeed reducing them to one temperature) to an accuracy at the limits of our ability to detect, in some cases a thousandth of a degree. Measurements that are made with no real understanding of the errors be they random or systematic.

Another, unnecessary, problem is that researchers use different units and there is a case for journals imposing common standards among the papers they publish to save researchers having to convert between W m-1 (expressed either for the entire Earth’s surface of for the ocean only), temperature or energy increase (often expressed in ZetaJoules). Also, as is often the case in climate studies, proper error bars are often not used.

Much of the heat, some claim, is stored deep in the ocean depths — but how did it get there? Timescales for ocean circulation are long, meaning that their depth have not yet seen what is happening at the surface. We do not understand centennial and millennial ocean circulation. We are seeing more references to cooling in the ocean depths. Some of our deep oceans appear to be still adjusting to the end of the Little Ice Age. Another significant finding is that the oceans appear to have absorbed as much heat in the early 20th century as in recent decades.

Some simplify and then exaggerate OHC data, a very foolish thing to do considering that as far as the oceans are concerned there is uncertainty at every point of the compass.

Feedback: david.whitehouse@thegwpf.com

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