So what's the story here?  Is there any real-world evidence that can be cited in support of these strident claims?  Orr et al. certainly make it appear such exists, but a little sleuthing reveals nothing of substance.

In support of this statement, we note that in response to increasing atmospheric CO2 concentrations, the 27 scientists say that "aqueous CO2 concentrations will increase and carbonate ion concentrations will decrease, making it more difficult for marine calcifying organisms to form biogenic calcium carbonate," whereupon they claim that "substantial experimental evidence indicates that calcification rates will decrease in low-latitude corals (Millero, 1995; Dickson, 1990; Dickson and Riley, 1979), which form reefs out of aragonite [a metastable form of calcium carbonate (CaCO3)], and in phytoplankton that form their tests (shells) out of calcite (Mucci, 1983; Bischoff et al., 1987), the stable form of CaCO3."  In reviewing the five papers cited in support of these contentions, however, we find that none of them deal with living organisms, and, therefore, that none of them deal with the actual calcification process as driven by life processes.  Rather, they deal exclusively with the lifeless world of chemistry and thermodynamics.

We have previously written extensively about the importance of letting life enter the picture, noting that coral calcification is much more than a simple (or even complex) physical-chemical process that can be described by a set of well-defined equations and constants, reiterating the fact that coral calcification is a biologically-driven physical-chemical process that may not yet be amenable to explicit mathematical description.  In this regard, we have reported (Idso et al., 2000) that "the photosynthetic activity of zooxanthellae is the chief source of energy for the energetically-expensive process of calcification," and we have stated that much evidence (for which we provided proper references) suggests that "long-term reef calcification rates generally rise in direct proportion to increases in rates of reef primary production," which suggests to us that "if an anthropogenic-induced increase in the transfer of CO2 from the atmosphere to the world's oceans were to lead to increases in coral symbiont photosynthesis - as atmospheric CO2 enrichment does for essentially all terrestrial plants - it is likely that increases in coral calcification rates would occur as well."

We have also noted that the calcium carbonate saturation state of seawater actually rises with an increase in temperature, countering the adverse oceanic chemistry consequences of an increase in aqueous CO2 concentration, which is a matter that is also considered by Orr et al., but which they dismiss as having a rather small effect, "typically counteracting less than 10% of the decrease due to the geochemical effect."  With this little problem thus dispatched, and ignoring the many ways in which life might enter the picture, they calculate that "relative to preindustrial conditions, invasion of anthropogenic CO2 has already reduced modern surface carbonate ion concentrations by more than 10%," while they calculate - "in agreement with previous predictions (Kleypas et al., 1999)" - that a 45% reduction relative to preindustrial levels may be reached by the end of the century, and that, ultimately, "rates of calcification could decline even further, to zero."  We, on the other hand, suggest they are grossly in error.

So what do studies of real-world corals and phytoplankton reveal about the various claims and counterclaims swirling about the issue?  Has the increase in atmospheric CO2 concentration experienced since the beginning of the Industrial Revolution, which is acknowledged to be unprecedented over the past 420,000 years (Petit et al., 1999), plus the 20th-century increase in temperature, which is claimed to be unprecedented over the past two millennia (Mann and Jones, 2003), seriously hampered coral and phytoplankton calcification rates?  If these historical environmental changes are as unprecedented and dangerous as the world's climate alarmists claim they are, we should be able to find plenty of evidence of their negative consequences.  But if we are right, we won't find any such evidence.  So let's see what the world's scientific archives have to say about the matter.

In a study of calcification rates of massive Porites coral colonies from the Great Barrier Reef (GBR), Lough and Barnes (1997) found that "the 20th century has witnessed the second highest period of above average calcification in the past 237 years."  Intrigued by this observation, they (Lough and Barnes, 2000) went on to assemble and analyze the calcification characteristics of 245 similar-sized massive colonies of Porites corals obtained from 29 reef sites located along the length, and across the breadth, of the GBR, which data spanned a latitudinal range of approximately 9° and an annual average sea surface temperature (SST) range of 25-27°C.  To these data they added other published data from the Hawaiian Archipelago (Grigg, 1981, 1997) and Phuket, Thailand (Scoffin et al., 1992), thereby extending the latitudinal range of the expanded data set to 20° and the annual average SST range to 23-29°C.

This analysis indicated that the GBR calcification data were linearly related to the average annual SST data, such that "a 1°C rise in average annual SST increased average annual calcification by 0.39 g cm^-2 year^-1."  Results were much the same for the extended data set; they report that "the regression equation [calcification = 0.33(SST) - 7.07] explained 83.6% of the variance in average annual calcification (F = 213.59, p less than 0.00)," noting that "this equation provides for a change in calcification rate of 0.33 g cm^-2 year^-1 for each 1°C change in average annual SST."

Noting that their results "allow assessment of possible impacts of global climate change on coral reef ecosystems," Lough and Barnes report that between the two 50-year periods 1880-1929 and 1930-1979, they calculated a mean calcification increase of 0.06 g cm^-2 year^-1; and they note that "this increase [our italics] of ~4% in calcification rate conflicts with the estimated decrease [our italics] in coral calcification rate of 6-14% over the same time period suggested by Kleypas et al. (1999) as a response to changes in ocean chemistry."  Even more stunning was their observation that between the two 20-year periods 1903-1922 and 1979-1998, "the SST-associated increase in calcification is estimated to be less than 5% in the northern GBR, ~12% in the central GBR, ~20% in the southern GBR and to increase dramatically (up to ~50%) to the south of the GBR."  In light of these real-world observations, and in stark contrast to the implications of the work of Kleypas et al. (1999) and Orr et al. (2005), Lough and Barnes concluded that coral calcification rates "may have already significantly increased [our italics] along the GBR in response to global climate change."

Another pair of scientists to address the subject was Bessat and Buigues (2001), who worked with a core retrieved from a massive Porites coral on the French Polynesian island of Moorea that covered the period 1801-1990, saying they undertook the study because they thought it "may provide information about long-term variability in the performance of coral reefs, allowing unnatural changes to be distinguished from natural variability."  This effort revealed that a 1°C increase in water temperature increased coral calcification rate by 4.5%, and that "instead of a 6-14% decline in calcification over the past 100 years computed by the Kleypas group, the calcification has increased."  They also observed patterns of "jumps or stages" in the record, which were characterized by an increase in the annual rate of calcification, particularly at the beginning of the past century "and in a more marked way around 1940, 1960 and 1976," stating once again that their results "do not confirm those predicted by the Kleypas et al. (1999) model," which is merely an earlier version of the Orr et al. model.

In spite of these real-world observations that refute the "lifeless" world view of Kleypas et al. and Orr et al., Buddemeier et al. (2004) have continued to claim that the ongoing rise in the air's CO2 content and its predicted ability to lower surface ocean water pH (which is also a key claim of Orr et al.) will dramatically decrease coral calcification rates, which they say could lead to "a slow-down or reversal of reef-building and the potential loss of reef structures in the future."  However, they have been forced to acknowledge that "temperature and calcification rates are correlated, and [real-world] corals have so far responded more to increases in water temperature (growing faster through increased metabolism and the increased photosynthetic rates of their zooxanthellae) than to decreases in carbonate ion concentration."

At about the same time, and following in the footsteps of Lough and Barnes who worked in the Indo-Pacific, Carricart-Ganivet (2004) developed relationships between coral calcification rate and annual average SST based on data collected from colonies of the reef-building coral Montastraea annularis at twelve locations in the Gulf of Mexico and the Caribbean Sea.  This work revealed that "calcification rate in the Gulf of Mexico increased 0.55 g cm^-2 year^-1 for each 1°C increase, while, in the Caribbean Sea, it increased 0.58 g cm^-2 year^-1 for each 1°C increase," a result nearly twice as great as that obtained by Lough and Barnes for Porites corals.  Further pooling these data "with those of M. annularis and M. faveolata, growing up to 10 m depth in Carrie Bow Cay, Belize, reported by Graus and Macintyre (1982), those of Dodge and Brass (1982) from all the reefs they studied at St. Croix, US Virgin Islands, and those of M. faveolata, growing up to 10 m depth in Curacao, Netherlands, Antilles, reported by Bosscher (1993)," Carricart-Ganivet reports he obtained a relationship of ~0.5 g cm^-2 year^-1 for each 1°C increase in annual average SST.

To these papers can be added many others that also depict increasing coral calcification rates in the face of rising temperatures and atmospheric CO2 concentrations, including those of Clausen and Roth (1975), Coles and Coles (1977), Kajiwara et al. (1995), Nie et al. (1997) and Reynaud-Vaganay et al. (1999).  As for why this is the way corals respond, McNeil et al. (2004) say that "observed increases in coral reef calcification with ocean warming are most likely due to an enhancement in coral metabolism and/or increases in photosynthetic rates of their symbiotic algae," just as we have done when noting over and over that coral calcification is a biologically-driven process that can overcome physical-chemical limitations that in the absence of life would appear to be insurmountable.

A second good reason for not believing that the ongoing rise in the air's CO2 content will lead to reduced oceanic pH and, therefore, lower calcification rates in the world's coral reefs, is that the same phenomenon that powers the twin processes of coral calcification and phytoplanktonic growth (photosynthesis) tends to increase the pH of marine waters (Gnaiger et al., 1978; Santhanam et al., 1994; Brussaard et al., 1996; Lindholm and Nummelin, 1999; Macedo et al., 2001; Hansen, 2002); and this phenomenon has been shown to have the ability to dramatically increase the pH of marine bays, lagoons and tidal pools (Gnaiger et al., 1978; Santhanam, 1994; Macedo et al., 2001; Hansen, 2002) as well as significantly enhance the surface water pH of areas as large as the North Sea (Brussaard et al., 1996).

Before concluding this editorial, we switch our focus from corals to phytoplankton in a review of the work of Riebesell (2004), who says that "doubling present-day atmospheric CO2 concentrations is predicted to cause a 20-40% reduction in biogenic calcification of the predominant calcifying organisms, the corals, coccolithophorids, and foraminifera."  In a challenge to this dogma, however, he notes that a moderate increase in CO2 actually facilitates photosynthetic carbon fixation of some phytoplankton groups, including the coccolithophorids Emiliania huxleyi and Gephyrocapsa oceanica.  In fact, Riebesell suggests that "CO2-sensitive taxa, such as the calcifying coccolithophorids, should therefore benefit more from the present increase in atmospheric CO2 compared to the non-calcifying diatoms."  An additional fact of importance, according to Riebesell, is that "the mechanism of calcification by coccolithophores is not completely understood."  This being the case, he feels it is definitely "too early ... to make any predictions regarding the physiological or ecological consequences of a CO2-related slow down in biogenic calcification."

Most significant of all, Riebesell reports some results of CO2 perturbation experiments conducted south of Bergen, Norway, where nine 11-m³ enclosures moored to a floating raft were aerated in triplicate with CO2-depleted, normal, and CO2-enriched air to achieve CO2 levels of 190, 370 and 710 ppm, simulating glacial, present day, and predicted conditions for the end of the century, respectively.  In the course of the study, a bloom consisting of a mixed phytoplankton community developed; and, in Riebesell's words, "significantly higher net community production was observed under elevated CO2 levels during the build-up of the bloom."  He further reports that "CO2-related differences in primary production continued after nutrient exhaustion, leading to higher production of transparent exopolymer particles under high CO2 conditions," something that has also been observed by Engel (2002) in a natural plankton assemblage and by Heemann (2002) in monospecific cultures of both diatoms and coccolithophores.  These particles, according to Riebesell, "accelerate particle aggregation and thereby enhance vertical particle flux," which he says may "provide an efficient pathway to channel dissolved and colloidal organic matter into the particulate pool."

Another important finding of this experiment was the fact that the community that developed under the high CO2 conditions expected for the end of the 21st century was dominated by Emiliania huxleyi.  Hence, Riebesell finds even more reason to believe that "coccolithophores may benefit from the present increase in atmospheric CO2 and related changes in seawater carbonate chemistry," in contrast to the many negative predictions that have been made about rising atmospheric CO2 concentrations in this regard.  Finally, in further commentary on the topic, Riebesell states that "increasing CO2 availability may improve the overall resource utilization of E. huxleyi and possibly of other fast-growing coccolithophore species," and he suggests that "if this provides an ecological advantage for coccolithophores, rising atmospheric CO2 could potentially increase the contribution of calcifying phytoplankton to overall primary production."

In spite of these several compelling observations, Riebesell says "it seems impossible at this point to provide a comprehensive and reliable forecast of large-scale and long-term biological responses to global environmental change," and that "any responsible consideration aiming to regulate or manipulate the earth system in an attempt to mitigate the greenhouse problem is presently hindered by the large gaps in our understanding of earth system regulation," implying (we presume) that proposed programs such as deep-ocean CO2 injection should not be implemented any time soon.  We agree, suggesting that this warning should also be applied to plans designed to regulate anthropogenic CO2 emissions, for there currently is no hard evidence from the real world of nature to suggest that calcifying organisms will be harmed by even a long-term continuation of the ongoing rise in the air's CO2 content, while there is considerable evidence to suggest they may be benefited thereby.

Clearly, we need to learn considerably more about these topics before we embark upon what could well be an ill-advised energy policy "course correction" that could actually work against our best interests, and against those of the rest of the biosphere as well.  Studies such as those of Orr et al., which fail to reflect what we know about the real and living world, in no way reflect the preponderance of current scientific thought on this subject ... even if each of them is the product of 27 authors from 8 different countries.

Sherwood, Keith and Craig Idso

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