Musings on Quantitative Palaeoecology

Pattern obfuscation of ocean pH

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I noticed that my blog had been cited by a couple of papers, so I went to have a look.

Albert Parker has a paper in Nonlinear Engineering. I’m sure this journal wasn’t chosen for the relevant expertise of the editors and usual pool of reviewers. More likely the converse: Parker (2016) is neither good nor original, a Gish gallop of a paper, recycling bad ideas from climate denialist blogs.

The paper returns repeatedly to the Monterey Bay pH time series, contrasting this series with the Hawaii Ocean Timeseries (HOT) from the North Pacific gyre. Parker prefers the Monterey Bay series, which does not show a decline in pH to the HOT data which show significant acidification (or as Parker would probably prefer, dealkalinisation).

Whereas the HOT data were explicitly designed to test for ocean acidification and  changes to the carbon inventory, the Monterey Bay series has a more immediate goal. The Monterey Bay Aquarium measures the chemistry of the water being pumped into their tanks from an intake 17m below the sea surface in the bay. Most of the time, the water at this depth is well-oxygenated surface water, but during upwelling events, cold, hypoxic, low-pH water is drawn into the pipe. The correlation between oxygen concentration and pH is high – 0.675 according to this Masters thesis which examines the time series in detail. The upwelling events, which occur more frequently in summer, add a large amount of variability to the data, obscuring any trend in ocean surface pH. The Monterey Bay pH series is in the perfect location if you want to avoid killing your fish with hypoxic water, but an utterly useless place if you want to test for ocean acidification: pH trends could be caused by ocean acidification or changes in upwelling. A better place would have much simpler hydrography, and so a much higher signal to noise ratio, perhaps an ocean gyre north of Hawaii. Parker complains that the IPCC ignores the Monterey Bay series. Of course they do. Anyone who uses the lack of trend in the Monterey Bay series as evidence against ocean acidification is clueless.

A couple of years ago Mike Wallace produced some excitement on climate denier blogs with a compilation of all historical pH measurements into a global mean which showed variability on multidecadal time scales. The problem is that the seasonal and geographical coverage of the pH measurement varies over time. Imagine if temperature data were most abundant in summer in northern Europe in the 1920s and then more common in east Asia and in winter in the 1990s, and then back to Europe after 2000, and that climatologists simply took the mean of the raw data. Obviously this would be junk: it is no less junk when done with pH measurements. Parker is unable or unwilling to understand this point. He has even read – or at least he cites – my blog, writing that I excuse the dismissal of the historical data because of “poor sampling protocols and non-gridded data”.  I think he should read it again.

Parker is not a fan of the HOT time series. pH was measured for two periods, between these measurements, pH was estimated by a “model”. The horror, the horror.

Closing the significant gaps with computer model results or extending the time range to 1988 by computer model results is not a legitimate procedure when there is no validation for the models. No model can be trusted if not validated first against accurate measurements, and if the measurements are not available or not accurate, than the use of the model is pointless. The time series of the actually measured pH does not satisfy the minimal quality requirements to infer any trend.

Since the HOT data are archived, we can for the very first time ever, validate the “model” against the measurements.

Calculated against measured pH. The r2 is 0.85.

I think this “model” can be trusted. Nevertheless, Parker, who should not be trusted, ignores the model data, but finds a significant decline in pH of −0.00157±0.00015 pH/year even though his model ignores the strong seasonality in the data. He wants to add extra uncertainty for measurement error: I don’t think he understands how linear models work. Because of some non-linearity in the trend, Parker decides that a 60-year sine wave would be a better model. Not on statistical grounds of course. Certainly not on physical grounds. His main attraction to the model seems to be that sine waves produce oscillations and that oscillations imply natural cycles.

There’s more. Much more. But it doesn’t get any better. For example

The measured surface CO2 from the NASA OCO-2 project differ considerably from the NOAA/PMEL estimated ocean CO2 and pH as proposed by Takahashi et al (2014)

Parker (2016) spent 10 months in review and revision. And still it is dross. But Parker obviously enjoyed the experience of publishing in Nonlinear Engineering as he has since published a second paper there under his alternative name Albert Boretti.

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