Only five Reef Check sites have both bleaching states in the same calendar month in 1998-2006 and 2007-2017

We counted support for before-and-after temperature comparisons in Reef Check records from the Global Coral-Bleaching Database, version 2. For 1998-2006 and 2007-2017, only five sites have positive and zero mean bleaching in the same calendar month in both periods. A less strict match has positive observations in both periods at 53 sites. Their mean temperature change is +0.691 C, with a 95 percent site bootstrap interval of +0.373 to +1.027. All surveys in the same cells change by +0.572 C. Site-only matching gives +0.038 C at 113 sites. A longer period split and a 10 percent bleaching rule give smaller or uncertain changes. Separate Atlantic and Pacific subsets do not give a clear common excess over all-survey warming. The added result is a matched-support audit that builds on prior campaign tests. Selected repeat sites, missing early outcomes, coarse exposure, and unknown survey effort prevent a biological threshold claim. Code, reduced surveys, cell contrasts, all estimates, provenance, and a figure are included.

coral bleaching · observation bias · survey timing · matched support · sea surface temperature