I'd be hesitant to believe there's a paper out there that shows long-term positive growth rates for corals in the GBR, even under extremely optimistic scenarios.

Of course not. But the corals on the NGBR bleached last year because of the worst El Nino event since 1998 (which incidentally decimated Indian Ocean reefs to an even larger extent, from 85% to below 5% coral cover, and they recovered within the decade).

And they bleached again not because the temperatures were more anomalous than three or four or five years ago but because these corals were still recovering from the El Nino stress - not much has been published on physiology yet (compared to all the surveying studies) but a large percentage of the corals that 'bleached again' didn't have time to recover in the first place. I can guarantee they hadn't recovered their symbiont populations or lipid reserves before the water started warming again.

You're absolutely right that back to back (to back to back) events have a way bigger impact on communities and many modeling studies use 'annual bleaching' as the timepoint when we say a region is going to be 'dead'.

But none of those studies take acclimatization into account. And corals have a ton of mechanisms for acclimatization, from switching symbionts to transcriptional acclimatization.

A study that came out maybe 2 years ago showed that fully half of thermotolerance is conveyed not by population-level adaptation but by transcriptional acclimatization.

That's hugely encouraging.