The basis for this new twist of logic is described in the brief note of Hoegh-Guldberg and Fine (2004) in the journal Coral Reefs, where the pair of marine biologists from the University of Queensland describe a significant episode of low-temperature-induced coral bleaching on the southern end of Australia's Great Barrier Reef.  In late July of 2003, they report that colonies of Acroporid corals in intertidal regions at Heron Island and nearby Wistari Reef and One Tree Island were exposed at low tide to extremely cold temperatures.  Subsequently, on 5 August 2003, bleaching was observed on the upper branches of exposed corals at all three sites, leading Hoegh-Guldberg and Fine to state that "cold conditions can have an almost identical outcome to warm water bleaching in coral reefs."  In fact, they went on to suggest that "bleaching during the winter months may be a natural phenomenon for high-latitude coral reefs," with which conclusion we agree; for Saxby et al. (2003) have also demonstrated that bleaching can be induced by cold temperatures, while Kobluk and Lysenko (1994) and Meehan and Ostrander (1997) have demonstrated that it is not so much temperature per se that leads to bleaching in corals, but rather the rapidity of change in either direction, i.e., warming or cooling.

If they had ended their short note at this point, all would have been well; but Hoegh-Guldberg and Fine proceeded to discover some new bad news in their observations, stating that projected changes in climate may lead to "greater variability in seasonal conditions," meaning that CO2-induced global warming may lead to both warmer and cooler temperatures, which is really a marvelous debating position, for whether corals are observed to bleach in response to unseasonably warm temperatures or unseasonably cool temperatures, it allows the producers and users of fossil-fuel-derived energy to be blamed for the biological devastation.  In essence, therefore, whatever bad things happen under this scenario, whether caused by warming or cooling, anthropogenic CO2 emissions can be held responsible for them.

Fortunately, real-world data tell a very different story from that which derives from the false premise upon which the two marine scientists build their environmental house of cards: on nearly all time scales, global warming leads to less variability in weather extremes of nearly all types, as may readily be seen in perusing the various materials archived under the many sub-headings of Weather Extremes in our Subject Index.  Most important within the context of coral bleaching, of course, is the sub-heading Weather Extremes (Temperature); and in reading the Summary of this section, one learns that whether the warming in question is from a glacial state to an interglacial, from a centennial-scale cool spell such as the Dark Ages Cold Period to a centennial-scale warm spell such as the Medieval Warm Period, or simply from the coolness of a La Niņa episode to the warmth of an El Niņo episode, temperature variability nearly always does just the opposite of what the world's climate alarmists claim and declines.

So, do not be misled by unsubstantiated claims and theoretical projections.  Search the scientific literature and see what real-world evidence has to say about the subject.  It is very apt to be something quite different from that which is promulgated by those who have a vested interest in promoting something (CO2-induced global warming) that is currently claimed, at the highest levels of many national governments, to be more serious than either nuclear warfare or international terrorism, and which currently serves as the sole means of support for their otherwise unsupportable policies of wanting to punish both the producers and users of fossil-fuel-derived energy.

References
Hoegh-Guldberg, O. and Fine, M.  2004.  Low temperatures cause coral bleaching.  Coral Reefs 23: 444.

Kobluk, D.R. and Lysenko, M.A.  1994.  "Ring" bleaching in southern Caribbean Agaricia agaricites during rapid water cooling.  Bulletin of Marine Science 54: 142-150.

Meehan, W.J. and Ostrander, G.K.  1997.  Coral bleaching: a potential biomarker of environmental stress.  Journal of Toxicology and Environmental Health 50: 529-552.

Saxby, T., Dennison, W.C. and Hoegh-Guldberg, O.  2003.  Photosynthetic responses of the coral Montipora digitata to cold temperature stress.  Marine Ecology Progress Series 248: 85-97.