Background
Climate alarmists mightily contend that global warming and ocean acidification -- both of which phenomena they attribute to anthropogenic CO2 emissions -- will shortly spell the end of earth's coral reefs, unless mankind brings a halt to the use of nearly all fossil fuels, and unless this is done rapidly.

What was done
The author, who hails from the Museum fur Naturkunde of the Leibniz Institute for Research on Evolution and Biodiversity at the Humboldt University in Berlin, reviews the state of mankind's knowledge of the long-term effects of changes in oceanic temperature and the atmosphere's CO2 concentration on the vigor of the planet's coral reefs as of 2009.

What was learned
With respect to global warming, Kiessling reports that "on geologic timescales, there is little evidence for climate change affecting reefs in a linear fashion," and that "changes in mean global temperature as reconstructed from stable oxygen isotopes and the distribution of non-reef climate-sensitive sediments do not correspond to changes in reef abundance or latitudinal distribution," citing some of his own analyses of the subject (Kiessling, 2001a, 2002). And he says that "reports linking reef expansions and declines to climate change fail to explain why other changes in temperature did not lead to a similar response in reefs and why the reported (fairly modest) temperature changes would have such a dramatic effect."

With respect to ocean acidification, the German researcher reports that "just like temperature," it is currently receiving much attention as "a control of reef development," but that "the boom and bust pattern of reefs and hyper-calcifiers is difficult to explain with inferred long-term changes in the saturation state of ocean water, at least if the major trigger is atmospheric pCO2," because "previous analyses failed to find any significant cross-correlation between changes in pCO2 and changes in reef attributes," citing Kiessling (2001b, 2002).

As a result of these and many other observations, Kiessling concludes that "neither climate nor sea-level nor chemical changes in the oceans can elucidate the waxing and waning of reefs" throughout their history on earth, stating that their "boom and bust pattern" is "impossible to explain by linear responses to physicochemical changes.

What it means
Kiessling states that "ecologically complex reef systems have been around for hundreds of millions if not billions of years," and that "geologic models of CO2 concentrations in the atmosphere suggest that these were much greater during most of earth's history than today," which further suggests that something other than CO2-induced global warming and ocean acidification must have been responsible for their prior "boom and bust" pattern of behavior.

References
Kiessling, W. 2001a. Paleoclimatic significance of Phanerozoic reefs. Geology 29: 751-754.

Kiessling, W. 2001b. Phanerozoic reef trends based on the Paleoreefs database. In: Stanley, G.D. (Ed.), The History and Sedimentology of Ancient Reef Systems. Plenum Press, New York, New York, USA, pp. 41-88.

Kiessling, W. 2002. Secular variations in the Phanerozoic reef ecosystem. In: Kiessling, W., Flugel, E. and Golonka, J. (Eds.) Phanerozoid Reef Patterns, Volume 22. Society of Economic and Paleontological Mineralogy, Tulsa, Oklahoma, USA, pp. 625-690.

Kiessling, W., Flugel, E. and Golonka, J., Eds. 2002. Phanerozoid Reef Patterns, Volume 22. Society of Economic and Paleontological Mineralogy, Tulsa, Oklahoma, USA, 775p.