The second chapter of Climate Change: The Facts 2017 is “Ocean Acidification: Not Yet a Catastrophe for the Great Barrier Reef” by Dr John Abbot and Dr Jennifer Marohasy. The first chapter is Peter Ridd’s critique of the mainstream of work on the reef.
The key points
Peer reviewed papers on ocean acidification came from nowhere between 2000 and 2004 to approach a peak near 800 published papers per annum in 2015.
This is a big issue in the press with regular reports that ocean acidification is one of the most alarming consequences of increasing CO2 in the atmosphere.
Most of these studies are conducted in laboratories which do not replicate the complexities of the ocean.
The indicator of acidity is number on a pH scale from 0 (pure acid) upwards with 7 the midpoint between the acid part of the scale and the base part of the scale.
The “acidification” that is reported is actually a small shift in the base part of the scale from figures in the order of 8.2 to figures around 7.8 to 7.9.
There is a lot of daily variation and some rock pools range in pH from 9.4 in the day to 7.5 at night. There are also seasonal variations.
Monitoring only started in the 1980s and there has been a very small trend down in that time but proxy estimates suggest that there are long-term cycles, as there are in temperature.
Several issues need to be addressed before claims of impending disaster for the reef can be taken seriously. These are publication bias, relevant timescales and levels of exposure, studies of ecosystems in the wild rather than single organisms in the laboratory, more attention to the variability in CO2, acidity and the different impacts on different organisms.
Stepping back through the key points starting with the dominance of laboratory studies. This is a very convenient way to work as I observed in the (then) Waite Agricultural Research Institute at the University of Adelaide circa 1967. People in wheat breeding and others using field trials could conduct one experiment per annum. For a PhD student that meant about three sets of data with the risk that a bad season seriously reduced their data base (or extend their student career which was no big deal in those more relaxed days). My work involved growing pea seedlings indoors and I could turn over a trial in three or four days. This obviously has massive implications given the imperative nowadays to publish papers to obtain grants and stay employed.
Abbot and Marohasy explain the basic chemistry of the acidity/non-acidity of sea water and the exchange between CO2 in the air and the various forms of Carbon in the water. The key indicator is the pH value that you should have discovered in high school. This is measured on a scale from 0 (pure acid) upwards with 7 the neutral midpoint. Below 7 is defined as “acidic” and above 7 is “basic”.
Looking at the “acidification” that causes so much alarm and comment, it turns out to be a shift that is very small compared with the natural variation recorded daily, seasonally and geographically. It would be more appropriately called neutralization. Daily variations can range from 9.4 to 7.5 and there are seasonal variations which exceed the margins in the order of 0.1 or 0.2 that prompt “alarm”.
Publication bias is an issue, as it is for all climate-related studies in the peer reviewed literature. See the East Anglia emails for insight into the credibility of the peer review system. The authors report that studies predicting disaster may be checked and shown to be wrong but the defective papers continue to be quoted in the media.
Timescales and exposure. Some laboratory studies use pH levels which exceed even worst-case climate change scenarios. They are short-term and make no allowance for acclimation, adaptation or evolution.
Extrapolation from the laboratory. The Free-Ocean CO2 Enrichment (FOCA) experimental approach is being developed to get over the limitations of lab trials. Preliminary results suggest that corals are much more durable and adaptable than you would think from the news.
Impacts depend on the organism. The organisms of concern are “marine calcifiers” that construct their shells or skeletons from calcium carbonate. This includes corals, crabs, clams and conchs (sea snails). According to popular science they are already severely impacted by the pH change but there turns out to be a very important difference between different types of coral with most showing no change in growth rate and considerable variation among the branching corals. This was the gist of Peter Ridd’s work which appears to shred the case for alarm if it is robust.
The authors conclude with some remarks about acidification in context. The issue “contains a grain of truth embedded in a mountain of nonsense.” The ocean has effectively limitless buffering to reduce the impact of CO2 on pH and so talk of acidification is strictly nonsense especially in light of the very small changes observed to date which are dwarfed by the natural variation.