[MarkPawelek (OP)]

I am sorry. I missed the wikipedia Henderson/Hasselbalch equation before. I will use their equation, but not their pKa because their equation is for blood, and pKa in seawater is slightly less than they give. I can use this for an alternative back-of-envelope equation, which I'm confident refutes NOAA too. I'll eat my hat if it does not.

[Bored chemist]

I am sorry. I missed the wikipedia Henderson/Hasselbalch equation before. I will use their equation, but not their pKa because their equation is for blood, and pKa in seawater is slightly less than they give. I can use this for an alternative back-of-envelope equation, which I'm confident refutes NOAA too. I'll eat my hat if it does not.

Go and buy a marzipan  hat (or maybe rice-paper if you don't like almonds)
We already have the numbers.
I already did the calculation .
The change is of the order or 24%

So, if your "improved" equation doesn't give an answer somewhere near what NOAA gave, you are simply wrong.

I don't understand why you are still trying to argue against reality.

[alancalverd]

So the pH value at one location off the coast of a volcanic island has changed a bit in the last 20 years. That's science.

" In the past 200 years alone, ocean water has become 30 percent more acidic" That's journalism.

The mean pH at Station Aloha seems to have levelled off around 8.08 between 2000 amd 2010. That's observation.

It will be interesting to see whether current volcanic events in the region have any noticeable effect. Science again.

Frankly, I have difficulty measuring pH of even fairly homogeneous stuff like blood, distilled water  or photographic chemicals to 3 significant figures in a laboratory. Given the depth, currents ,temperature variability, weather variability ,rainfall, evaporation, and pseudocyclic ecology at every depth of the Pacific Ocean, I'm not sure what "ocean pH at Aloha" even means, let alone how it is measured to 4 or 5 sig figs with a 200-year-old electrode, nor what its global significance may be.

We live in an unstable world. Fact.

[chiralSPO]

I am sorry. I missed the wikipedia Henderson/Hasselbalch equation [nofollow] before. I will use their equation, but not their pKa because their equation is for blood, and pKa in seawater is slightly less than they give. I can use this for an alternative back-of-envelope equation, which I'm confident refutes NOAA too. I'll eat my hat if it does not.

So what flavor is your hat?

[Bored chemist]

Frankly, I have difficulty measuring pH of even fairly homogeneous stuff like blood, distilled water  or photographic chemicals to 3 significant figures in a laboratory.

There is no mechanism by which your incompetence affects other people's results.
Part of your problem may involve
(1) thinking blood is homogeneous (the pH inside a red blood cell is different from the pH outside it)
(2) failing to understand the effects of buffering capacity when trying to measure the pH of very dilute solutions such as distilled water - You did remember to use a double junction electrode, didn't you?
(3) failing to take account of reactions of the silver/ silver chloride electrode commonly used as a reference with thiosulphate (specifically used because it reacts with silver salts) and  photographic developers which are... also specifically chosen because they react with silver salts.

There are probably other issues.

The mean pH at Station Aloha seems to have levelled off around 8.08 between 2000 amd 2010. That's observation.

No, the data show a clear downward trend.
That's the real observation

" In the past 200 years alone, ocean water has become 30 percent more acidic" That's journalism.

Rounding the data to "30%" is reasonable as both journalism and as a scientific presentation of a valid extrapolation of the data.

It will be interesting to see whether current volcanic events in the region have any noticeable effect. Science again.

True, but that effect will be local, rather than global so it isn't strongly related to the worldwide issue.

I'm not sure what "ocean pH at Aloha" even means, let alone how it is measured to 4 or 5 sig figs with a 200-year-old electrode

Nobody said it would.

Are you planning to share a headgear based meal with Mark?

[alancalverd]

Someone has chosen to fit  a straight line to the 1988-2006 data. But I think you would get a better fit with a steeper line up to 2000 and a shallower one thereafter. A classic example of making the data fit the model, which can lead to policy-based evidence-making, self-deception, and all sorts of flat-earth nonsense if unchecked.

To revert to the OP

In the past 200 years alone, ocean water has become 30 percent more acidic

looks to me like a global statement of historic results, but the only evidence presented in this discussion seems to be 18 years' data from one admittedly unstable and uncharacteristic point on the globe, and a linear regression with R² < 0.3 indicating that the data is mostly noise or nonlinear.

Remember the old joke about three men in a train, seeing two cows in Patagonia

Politician: "The vast majority of Patagonian cows are black"

Mathematician: "On an insignificant sample, one might hypothesise that half the cows in Patagonia are black"

Physicist: "0300 UTC, Patagonia. Two bovine quadrupeds observed, at least one side of one of which is black."

Happy to eat a hat made from nori or plaited sea spaghetti, but not just yet.

[evan_au]

The pH is not the same everywhere because the ocean is not mixed perfectly well.

This struck me while looking at the graph - the concentration of CO₂ in the ocean does not track the concentration of CO₂ in the atmosphere very well.
- However, the concentration of CO₂ in the ocean is strongly (inversely) correlated with the pH of the ocean, suggesting that dissolved CO₂ is a major driver of ocean acidification.

So maybe ocean currents, winds or el Nino bring deep water to the surface, which reflect an older (lower) concentration of atmospheric  CO₂?
- Of course, as the surface waters laden with increased CO₂ cool and descend to lower depths at the poles, this reservoir of  slightly higher pH will be consumed.

[alancalverd]

As far as I can tell by simply zooming on the graph, the ocean p[CO₂] exactly anticorrelates with the atmospheric value. This isn't entirely surprising as we know that the seasonal variation of atmospheric  p[CO₂] at Mauna Loa is itself anomalous - the maximum concentration each year occurs in summer, when the anthropogenic emission is lowest.

So we are back to known chemistry: for a given atmospheric partial pressure, the equilibrium concentration of CO₂  in water decreases with increasing temperature.

Edit: And now I realise that this will cause confusion! p[X] is standard nomenclature for partial pressure of a dissolved gas and increases with concentration [X], whilst pH is an inverse function of [H⁺]!

[jeffreyH]

Care need to be taken when interpreting data. Do we know the intricate workings of our own atmosphere or could we learn by studying other examples?
https://www.newscientist.com/article/dn22572-heavy-hydrogen-excess-hints-at-martian-vapour-loss/

[Bored chemist]

People are now playing a new game.
It's called "I can interpret this graphical representation of the data, better than the people who generated (and thus had access to) the real data."

It's great fun.
It isn't science.

This isn't entirely surprising as we know that the seasonal variation of atmospheric  p[CO2] at Mauna Loa is itself anomalous - the maximum concentration each year occurs in summer, when the anthropogenic emission is lowest.

With a seasonal variation from 20 to 24 C over the year, Hawaii hardly has a Summer to be anomalous about.

Seasonal CO2 variation is fairly well understood.
https://scripps.ucsd.edu/programs/keelingcurve/2013/05/07/why-are-seasonal-co2-fluctuations-strongest-in-northern-latitudes/

[Bored chemist]

As far as I can tell by simply zooming on the graph, the ocean p[CO2] exactly anticorrelates with the atmospheric value.

Are we talking about the same graph?
graph cropped.png (110.32 kB . 253x261 - viewed 4544 times)

Are you saying that the red dots go up, and the blue ones go down, or the other way round?

[jeffreyH]

The planet will still be here long after the human race is gone. The universe isn't here to be kind to us. Maybe we should stop examining our own navels.

[alancalverd]

The Scripps link is interesting.  Fortunately the first Comment offers a more comprehensive  explanation of what actually happens in one sentence, but it is noticeable that the principal student essay is a bit vague about the actual phasing and amplitude of the cycle.

And yes, the expanded graph does show an anticorrelation between atmospheric and ocean CO2.

Both observations are entirely consistent with what we learned at school about biology and physical chemistry. It's just interesting to see how nature behaves on a large scale pretty much as it does in a test tube.

As for "offering a better interpretation" of someone else's data, it is mere curiosity that makes me wonder why anyone would fit a straight line to data that does not appear linear and indeed cannot be linear.

Nor would I dismiss the obvious seasonal cycle of Mauna Loa CO2 concentration (which is so regular and so significant that the observers themselves draw attention to it) because "With a seasonal variation from 20 to 24 C over the year, Hawaii hardly has a Summer to be anomalous about." The job of science is to explain what happens, not to pretend it can't.

The outstanding problem with climate science is the damn data!

[Bored chemist]

the expanded graph does show an anticorrelation between atmospheric and ocean CO2.

Seriously?
What graph do you mean, and what do you mean by anti-correlation?

[chiralSPO]

The overall trend-lines for each are definitely correlated. It is hard to tell from the graphic without expanding, but it looks like the noise could be anti-correlated. This could make sense, as the overall amount of CO₂ is increasing, as indicated by both trend-lines, but day-to-day (or whatever) variations in temperature will cause the distribution of CO₂ to differ-with warmer temperatures increasing atmospheric concentrations at the expense of marine concentrations, while cooler temperatures increase marine concentrations at the expense of atmospheric.

The main takeaway, however, should not be the relationship between noise in the data, as there is no systemic error indicated. Rather, we should be concerned with the overall trend.

[Bored chemist]

It's possible that the noise has an inverse correlation.
Who cares?
The measured variables are clearly correlated.

[alancalverd]

Here in the real world, we take every measurement as a measurement. Xome folk deduce "signal" by imposing a model on a sequence of measurements, and dismiss the variances from that model as "noise", but whilst that is the way of politics, philosophy, religion and economics, it isn't good science.

I looked at the expanded graph of seasonal variation of atmospheric [CO2]   and compared it point-by-point with the ocean [CO2] concentration. What comes out of that comparison is that ocean [CO2] decreases in the short term  as the temperature rises, which is entirely to be expected, but as I have remarked before, atmospheric [CO2] increases anomalously as temperature rises in the northern hemisphere.

You can of course draw crude trend lines through all the data, but I think that misses a lot of interesting information. There is no doubt that atmospheric and ocean [CO2] have risen over the periods measured, but the short-term detail suggests that the underlying mechanism is more interesting than merely "anthropogenic". That's the problem with science - it makes us question what civilians dismiss as "obvious", and leads to all sorts of things like aeroplanes, nuclear power, antibiotics.....

[Bored chemist]

You are right- assuming that we wish to look at the CO2 in air and sea, but ignore the effect of time - which is important in the real world.
All you have done is highlight a phase lag. It's interesting in it's way. Obviously, it's an artefact of a system that's being driven by a "rapidly" osculating  driver- the Sun's annual variation. It's a little like the observation that, in the UK at night time the sea is hottest (compared to the air) in Autumn, rather than Summer even though the weather in general is hottest in Summer.
But the fact is that both are rising with time.

You say "but the short-term detail suggests that the underlying mechanism is more interesting than merely "anthropogenic"."
well, that's "sort of" good- because nobody was saying the short term variation was anthropogenic.
The thing we need to do something about is the bloody great big change. The change that's driven by anthropocentric releases of CO2 that we know about, and can quantify quite well by either looking at fuel duty receipts in government taxes or at profits of oil companies. (we can also get better estimates, but those ones are good enough) to show the point.
The noise on that may be correlated any which way- but it's weather rather than climate.

[alancalverd]

It is the phase relationship between temperature and CO2 that questions the accepted "wisdom" of anthropogenic climate change.

Drawing straight lines through wobbly data is a reasonable way of demonstrating gross correlation to a naive audience, but temporal phase analysis demonstrates causality

[Bored chemist]

Drawing straight lines through wobbly data

You have plausibility to the extent that this trend is "wobbly"

wobbly.JPG (29.08 kB . 442x221 - viewed 4450 times)