Jennifer Marohasy concurs that the AIMS GBR study presents level 5 evidence (merely expert opinion) that measured decline in coral growth is due to anthropogenic global warming.
Indeed no data is presented to suggest the PH (a measure of acidity) of GBR waters has changed.
Confronted with a lack of evidence in support of this hypothesis â€“ that ocean acidification has caused the drop in growth rates â€“ the researchers suggest in the paper â€œsynergistic effects of several forms of environmental stressâ€ and implicate higher temperatures. But no data is presented in the paper to contradict the well established relationship between increasing temperature and increasing growth rates â€“ though various confusing statements are made and it is suggested that global warming has increased the incidence of heat stress in turn reducing growth rates â€“ while at the same time the researchers acknowledge higher growth rates in northern, warmer, GBR waters.
In a further swipe at global warming zealotry, squarely at the exaggeration of low quality of evidence, she quotes:
Marine Biologist Walter Starck has perhaps aptly described the research as part of â€œthe proliferation of subprime research presenting low value findings as policy grade evidenceâ€ and has suggested this has â€œscience headed in the same direction as Wall Street.â€
Interestingly, Queensland Premier, Anna Bligh, has decided the â€œmassive decline in the reefâ€™s growthâ€ will require new laws.
CSIRO and AIMS race each other to the bottom of the science quality ladder.
What can be done? I have frequently advocated the adoption of a quality of evidence rating modeled on the Oxford Evidence Scale, applied to all research with policy implications, particularly global warming. This could easily be implemented on an institution-wide (CSIRO, AIMS, etc.) basis.
The main benefits would be a quick indication of how much weight to place on a particular piece of research, and a quantitative measure of improvements in research quality over time.
In the comments section of Jennifer’s post, Walter Starck indicates the downturn may be an artifact of the statistical smoothing methodology (sound familiar?).
The purported slowing of coral growth rates on the GBR appears to be a remake of â€œThe Hockeystickâ€ with Splines playing the role of Principal Component Analysis. Deâ€™ath et al. offer no actual growth data in the paper or online supporting evidence. What they present are splines derived from the data. These depict a dramatic reduction in growth after 1990. During this period the GBR suffered two severe bleaching events in 1998 and 2002. Both were associated with El NiÃ±o induced extended summer calms and resultant SST spikes.
Splines are only a curve fitting tool and various different splines can be constructed to fit the same data. In this instance it is apparent that the knots chosen for construction of these particular splines are ones which result in a sharp downturn after 1990 due to the hiatus in growth from the bleaching events. This is obvious from the fact that neither the bleaching events nor the subsequent recovery appear as distinct changes in the curves but have both been smoothed into a sharp decline continuing down to the end in 2005. That the data set ends in 2005 also helps in exaggerating the decline by truncating the ongoing recovery in growth after the 2002 bleaching.
Interestingly this study comes only a few days after the report that recovery of corals from the Boxing Day tsunami has been found to be occurring much faster than expected.
It would be productive to get the raw data plotted and reanalyzed. Any takers?