Yu, K.-F., Zhao, J.-X., Shi, Q., Chen, T.-G., Wang, P.-X., Collerson, K.D. and Liu, T.-S. 2006. U-series dating of dead Porites corals in the South China sea: Evidence for episodic coral mortality over the past two centuries. Quaternary Geochronology 1: 129-141.
The authors write that "prior to the late 1960s, reports of coral bleaching were scattered or almost nonexistent," and, therefore, they state that "many ecologists consider that large-scale mass bleaching is a new phenomenon," which view is used by the world's climate alarmists to support their contention that warming over the last two decades of the 20th century was unprecedented over prior centuries to millennia ... or even the past million years (Hansen et al., 2006).
What was done
In a study well suited to explore this particular aspect of this persistent claim, Yu et al. describe how they "dated massive Porites and microatolls on the reef flats of Younshu and Meiji Reefs, Nansha area, southern South China Sea using high-precision thermal ionization mass spectrometric (TIMS) U-series dating techniques," noting that these reefs "are directly influenced by the Western Pacific Warm Pool."
What was learned
The seven scientists report that "at least six mortality events occurred simultaneously on both reefs (e.g. in 1869-1873, 1917-1920, 1957-1961, 1971, 1982-1983 and 1999-2000 AD), reflecting the occurrence of large-scale regional events." In addition, they say that "many of these mortality events appear to correlate in time with historic El Niņo events, and were probably related to El Niņo-induced high sea surface temperature bleaching."
What it means
In the words of Yu et al., their study "demonstrates that individual colonies of massive corals have died at different times over the past two centuries," which suggests that sea surface temperatures of the Western Pacific Warm Pool were likely just as warm during those earlier bleachings as they were during the bleachings of the latter part of the 20th century. And this inference suggests that that "this critical ocean region," as Hansen et al. (2006) refer to it, may not be any warmer now than it was a number of times over the past two centuries, in contradiction of their strident claim to the contrary.
Hansen, J., Sato, M., Ruedy, R., Lo, K., Lea, D.W. and Medina-Elizade, M. 2006. Global temperature change. Proceedings of the National Academy of Sciences USA 103: 14,288-14,293.