Coral bleaching is a stress response, not an immediate finding of death. NOAA explains that stressed corals lose their symbiotic algae; survival is possible, while prolonged loss and continuing stress can be fatal. A heat-stress warning and a photograph therefore answer different questions. NOAA survival explanation

Pale, brown and subtly fluorescent coral beneath a warm-water ribbon

Conceptual illustration, not an observed reef or forecast.

Read the biological observation

AIMS explains that algae loss makes the white skeleton visible through the tissue. Some bleaching instead appears fluorescent pink, yellow or blue. Survivors can still have slower growth, reduced reproduction or disease susceptibility. Color returning is consequently insufficient evidence of complete recovery. AIMS appearance and recovery guidance

When reading a report, identify what its authors actually observed. Was the photograph taken at one colony, or was a survey designed to describe a wider area? Does the statement concern appearance at that visit, or later survival? These are questions to ask of the report, not extra observations to invent from an image. Keep the location and observation date attached when repeating its conclusion.

Keep the metric and accumulation threshold separate

NOAA defines HotSpot as sea-surface temperature minus the local Maximum Monthly Mean, the highest monthly climatological mean. Positive values below 1°C exist. DHW sums the full daily HotSpot values that are at least 1°C over 84 days, divided by seven, in °C-weeks. It does not sum only the excess above 1°C. NOAA metric definition and formula

The DHW product associates 4°C-weeks with bleaching risk and 8°C-weeks with likely reef-wide bleaching and mortality of heat-sensitive corals. These are monitoring risk interpretations, not certain outcomes for each colony. Product risk interpretation

Before comparing two numbers, check that both labels refer to DHW rather than one being a temperature anomaly. Also retain the units: a temperature difference and an accumulated heat-stress value describe different quantities. A reader should not have to reconstruct which quantity a headline used from the color of its map.

A quieter map does not prove recovery

NOAA's single-day alert uses that day's HotSpot and DHW together. A location classified as No Stress can still have recent heat exposure. The product's current category should not be read as a biological recovery finding. Single-day alert and recent exposure

For an illustrative reading exercise, imagine a report with a high earlier DHW value, a later quieter alert and a pale-coral photograph. Write three separate statements: the heat exposure recorded earlier, the later product classification, and the photographed appearance. Leave survival unresolved unless an appropriate follow-up observation supplies it. The purpose is to preserve the evidence behind each sentence, rather than turn all three into a single claim that the reef recovered.

Keep the study's target and dates visible

Little and colleagues' 2022 analysis used monthly maximum DHW derived from 5km CoralTemp v3.1 for 1985–2018 and 25km OISST v2 for 1982–2018. Its 5km broad-event rule counted reef pixels at DHW≥4°C-weeks, using a 10% threshold in each of three tropical basins and an eight-month detection window. This historical detection choice is not a recovery deadline or an individual mortality prediction. Research datasets and detection scope

Do not rename the percentage as the share of corals that died: its counted unit is reef-containing pixels exposed to the specified heat stress. Likewise, keep a paper's historical end date when describing what it analyzed. This article does not supply a current global bleaching percentage, a country total or a dated measurement from today's map.

Expert perspective: ask for local evidence

AIMS describes Great Barrier Reef weather stations and temperature loggers, and compares conditions with reef-specific thresholds informed by past events and local records. That institutional practice adds local observing context; it is not a claim of worldwide field-survey coverage. Specialist early-warning practice

A useful report separates the warning, the observed bleaching and the later outcome. Ask which reef was surveyed, what was measured and whether follow-up exists. If those details are absent, state the limit openly. This keeps a warning useful without pretending it has already measured the final ecological result.

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