New Study: Coral Bleaching ‘Repeatedly Occurred’ Throughout The Warmer-Than-Today Mid-Holocene

Mid-Holocene South China Sea maximum temperatures were ~3.5°C warmer (33.5°C vs. today’s 29.9°C) about 5000 yrs ago, when corals experienced an “optimum coral growth period”. There were “numerous coral bleaching episodes” even when temperatures weren’t as high, as coral bleaching is naturally occurring.

Key points from a  new study (Wang et al., 2021) that throws cold water on the claims that modern coral bleaching is unprecedented, unusual, or unnatural.

• “Compared with the average Sr/Ca-SST of the 1990s, the Sr/Ca-SST between 6800 and 5000 B.P. was 0.9°C–0.5°C higher.”

• “A warmer climate makes the mid-Holocene an optimum coral growth period when corals grew abundantly (Clark et al., 2018; Yan et al., 2019).”

• “During the period 3434–4568 B.P., the climate was colder than 6.8–5.0 ka B.P., but there were numerous coral bleaching episodes.”

• “[C]oral bleaching caused by thermal stress has been repeated over the long-term scale of the mid-late Holocene period and severe or prolonged coral bleaching events can lead to massive coral death.”

• “[T]he mid-late Holocene coral thermal bleaching events are a natural response to abnormal temperature.”

• There is “evidence of rapid recovery after bleaching” and “coral bleaching events have occurred repeatedly in the mid-late Holocene during times of high SST, and corals have proved to be resilient despite this environmental stress.”

Image Source: Wang et al., 2021

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January 18, 2021 at 11:00AM