Heat that bleaches coral reached 84% of the world's reefs
Share of global coral reef area under bleaching-level heat stress in each global bleaching event, 1998–2025.
Heat stress strong enough to bleach coral reached 84% of the world's reef area in 2023–2025.
That is four times the reach of the first global event in 1998 (21%).
Mass bleaching was recorded in at least 83 countries and territories.
the numbers
| Reef area under bleaching-level heat stress (%) | |
|---|---|
| 1st event, 1998 | 21 |
| 2nd event, 2010 | 37 |
| 3rd event, 2014–2017 | 68 |
| 4th event, 2023–2025 | 84 |
source notes & method
Percentages are NOAA Coral Reef Watch satellite heat-stress estimates (bleaching-level heat stress, not confirmed bleaching on every reef). The 84% and 83 countries are confirmed by NOAA NCEI (scijinks.gov/news/worlds-fourth-mass-coral-bleaching-event-likely-ended-2025); 1998, 2010 and 2014–2017 shares are as reported by GCRMN citing NOAA CRW. Events differ in length (the third and fourth lasted about 3 and 2.5 years). The fourth event began early 2023 and likely ended mid-2025. Replaces the planned Dead Sea level plate: no primary Israel Hydrological Service series could be retrieved.
Published 3 Nov 2026
what connects to this
one plate, every morning
The new world, explained in one chart, in your inbox at 7:00, your time. Free.
or follow via rss, the "rss" in progrss