Rainfall gave no clear heat-response reduction in four Atlantic and Pacific coral samples from 2003 to 2019

We tested whether rain before a coral survey marked a smaller bleaching response to heat. We joined Reef Check records to monthly GPCP rain data. Four models used 5,336 repeat-site monthly records in the Atlantic and Pacific in 2003-2010 and 2011-2019. Models controlled site, year, survey month and depth. Heat-slope changes per 1 mm/day rain anomaly were -4.23, +2.47, -0.99 and -0.76 bleaching points per four degree-heating weeks. All four adjusted intervals included zero. Six checks per sample also gave uncertain changes. Rain terms gave no clear link to the share of samples with reported bleaching values. This does not show that rain has no effect. Coarse rain cells, few high-heat records, selected surveys and unmeasured coral types limit inference. Heat can carry part of the rain effect, so this test cannot estimate total rain protection. Code, the joined panel, source hashes, checks and a figure are included.

coral bleaching · rainfall · heat stress · observation bias · regional replication · GPCP