The Curry test for ocean acidification

There’s a recent post about ocean acidification on Judith Curry’s blog, Climate Etc. She includes the commentary from two opposing views on this topic and then weighs up the evidence herself and decides whose views she finds more credible.  The two points of view come from these two people:

* Scott C. Doney – senior scientist at the Woods Hole Oceanographic Institution. He has a Ph.D. in chemical oceanography and his research interests are marine biogeochemistry, ocean acidification, global carbon cycle, and climate change.

* Craig D. Idso – founder and chairman of the Center for the Study of Carbon Dioxide and Global Change. He has a Ph.D. in Geography and reportedly receives $11,600 per month from the Heartland Institute. The Heartland Institute is a right-wing think tank which no longer discloses its sources of funding but has previously received money from Exxon Mobil and in the 1990s worked for big tobacco to question the science linking smoking with cancer. He is not affiliated with any university and has not had anything published in a scientific journal that I could find.

I am quite surprised that for the contrary view, Curry has chosen Craig Idso who does not have a speciality in this area but who has a conflict of interest which she does not mention. For these reasons, I would give more weight to the views of Scott Doney. Craig Idso also uses some quite emotive language in his story like “extreme one-sided” and “propagandized view”.

Despite all of this, Judith Curry scores Idso’s story more highly than Doney’s. Her reason for doing so is because she says Doney’s testimony is normative. What does normative mean? It’s the apparent subtle inclusion of policy arguments when presenting scientific information through the use of value-laden words like “degradation”, “good” or “poor” . Curry concludes that Idso’s testimony is normative because she conducts a word search of his testimony and does not find many statements with the words “uncertain”, “disagreement”, “debate” or “unknown”. Here’s what she says:

I found Doney’s testimony to be highly normative, something that I am not a fan of in testimony by scientists.  I did a word search, looking for ‘uncertain’, ‘disagreement’, ‘debate’, ‘unknown’.  The only statements I found were:

She then copies and pastes two sentences that do include some of these words and goes on to say,

For these reasons, Doney’s testimony didn’t score too high on my credibility meter, in spite of my acknowledgement of his expertise and stature in the field.

Does this seem a little odd to anyone else? I think Judith Curry is trying to suggest that Doney’s research is driven by certain underlying assumptions and biases but I cannot see how the inclusion or exclusion of words like “uncertain” or “disagreement” is evidence of this. My conclusion is that if an expert in the field of ocean acidification is describing current knowledge without littering their description with the words “uncertain” or “disagreement” then this is probably a reflection of the level of scientific consensus in this area rather than a covert attempt to sway public policy.

I acknowledge that I am probably biased – I am not a fan of the heat and I love coral reefs and I have unwavering respect for science – so I am going to paste some of Scott Doney’s testimony to the Committee on Environment and Public Works here below and completely ignore the views of Craig Idso. If anyone wants to see whether there is a contrary view and what it is, I would recommend going to your local library (a method for research I learnt in primary school) and search the peer-reviewed literature for “ocean acidification” and “coral” or “marine organisms” or something similar. This is what I have done and there is more support for Doney’s views than for Idso’s in my humble opinion.


The ocean uptake of excess atmospheric carbon dioxide, the excess above preindustrial levels driven by human emissions, causes well-understood and substantial changes in seawater chemistry that can affect marine organisms and ecosystems(Doney et al., 2009; Gattuso & Hansson, 2011). Carbon dioxide (CO2) acts as a weak acid when added to seawater leading to the release of hydrogen ions (H+) and bicarbonate (HCO3) ions:

CO2 + H2O => H+ + HCO3

The reaction increases seawater acidity and increases the hydrogen ion activity, thus lowering seawater pH. pH is defined as the negative logarithm of the hydrogen ion activity, so that a 1-unit change in pH is equivalent to a 10-fold change in H+. Most of the extra hydrogen ions react with carbonate ions (CO32-) and lower their ambient concentrations:
H+ + CO32- => HCO3

This second reaction is important because reduced seawater carbonate ion concentrations decrease the saturation levels of calcium carbonate (CaCO3), a hard mineral used by many marine microbes, plants and animals to form shells and skeletons. Many organisms require supersaturated conditions to form sufficient calcium carbonate shells or skeletons, and biological calcification rates tend to decrease in response to lower carbonate ion concentrations, even when the ambient seawater is still supersaturated.

I think it’s also worth mentioning that the coral reefs have disappeared in the past. According to reef ecologist, Peter Sale, the world’s coral reefs completely disappeared in each of the previous five mass extinctions and they were gone for tens of millions of years at a time.

A different article from the journal Nature from 2011, Earth’s Acid Test, has something similar to say:

Some 55 million years ago, during an episode of extreme global warming driven by a spike in atmospheric CO2, the pH of sea water is thought to have dropped to levels similar to those expected at the end of the twenty-first century. Ocean sediment deposited during that period contains very little carbonate and no fossils of microorganisms with calcium carbonate shells, indicating that the sea water became too corrosive for calcifying algae such as deep-sea foraminifera, driving many to extinction. Today, acidification is progressing at least ten times faster than it did 55 million years ago.

Below is a graph from the same paper which shows how rising carbon dioxide and ocean pH will affect different organisms at different times. The coloured lines represent four different carbon emissions scenarios. Click to enlarge.