NOAA NESDIS Center for Satellite Applications and Research, Coral Reef Watch
NOAA Coral Reef Watch coral bleaching heat stress and global bleaching status
Coral bleaching heat stress from Coral Reef Watch's daily global 5 km satellite product suite, version 3.1 (CoralTemp sea surface temperature, from 1985). Degree Heating Weeks (DHW, in degree Celsius-weeks) accumulate, over the past 12 weeks, the days when the sea was more than 1 °C warmer than its usual warmest-month average, weighted by how much warmer; CRW says values over 4 °C-weeks have caused significant bleaching and over 8 °C-weeks severe bleaching and significant mortality. Registered here: the annual maximum DHW maps for 2023, 2024 and 2025, the years of the fourth global bleaching event, and CRW's global bleaching status page, which publishes the share of the world's coral reef area that had bleaching-level heat stress (about 84.4% from 1 January 2023 to 30 September 2025; 68.2% in 2014-2017). Those percentages are CRW's published values; recomputing them needs CRW's reef-pixel definition. Heat stress is a measure of risk, not of observed bleaching or coral death.
Numbers published from it
Licence and credit
- What the terms say
“NOAA Coral Reef Watch (CRW) data posted on the internet are freely available to the public. All content on this website is considered to be in the public domain and may be distributed freely.”
From the producer's terms, checked 2026-10-04; re-checked automatically every week.
- Credit we give
- NOAA Coral Reef Watch, Version 3.1 Daily Global 5km Satellite Coral Bleaching Heat Stress products (Skirving et al. 2020, Remote Sensing 12, 3856, doi:10.3390/rs12233856), accessed {date_accessed}.
- Copy of the raw file
- Allowed: we keep a public copy of every version we use.
- Cite as
- NOAA Coral Reef Watch. 2018, updated daily. NOAA Coral Reef Watch Version 3.1 Daily Global 5km Satellite Coral Bleaching Degree Heating Week Product, Jan. 1, 2023-Dec. 31, 2025. College Park, Maryland, USA: NOAA Coral Reef Watch. Data set accessed {date_accessed} at https://www.star.nesdis.noaa.gov/pub/socd/mecb/crw/data/5km/v3.1_op/nc/v1.0/annual/. Skirving, W; Marsh, B; De La Cour, J; Liu, G; Harris, A; Maturi, E; Geiger, E; Eakin, CM. CoralTemp and the Coral Reef Watch Coral Bleaching Heat Stress Product Suite Version 3.1. Remote Sens. 2020, 12, 3856; https://doi.org/10.3390/rs12233856.
Files
CRW's "Current Global Bleaching: Status Update" page (updated 2 June 2026): the published share of global reef area under bleaching-level heat stress in the fourth (2023-2025) and third (2014-2017) global events and the count of countries and territories with documented mass bleaching.
https://coralreefwatch.noaa.gov/satellite/research/coral_bleaching_report.phpAnnual maximum Degree Heating Week for 2023, global 0.05-degree grid (degree_heating_week x 0.01, date of first occurrence, pixel mask).
https://www.star.nesdis.noaa.gov/pub/socd/mecb/crw/data/5km/v3.1_op/nc/v1.0/annual/ct5km_dhw-max_v3.1_2023.ncAnnual maximum Degree Heating Week for 2024, same layout.
https://www.star.nesdis.noaa.gov/pub/socd/mecb/crw/data/5km/v3.1_op/nc/v1.0/annual/ct5km_dhw-max_v3.1_2024.ncAnnual maximum Degree Heating Week for 2025, same layout.
https://www.star.nesdis.noaa.gov/pub/socd/mecb/crw/data/5km/v3.1_op/nc/v1.0/annual/ct5km_dhw-max_v3.1_2025.nc
Status
- Programme
- Daily products are current (the daily DHW file for 3 October 2026 was posted on 4 October). The status page was last updated on 2 June 2026, when NOAA said the fourth global bleaching event likely ended in 2025. The FY2027 US budget request (April 2026) proposes terminating NOAA's Coral Reef Conservation Program, while listing "Maintain ecological forecasting for coral bleaching via the coral reef watch program (ongoing)" among its objectives.
- Updates
- Daily (5 km products); annual composites each January; status page when events warrant
- Last check
- Unchanged since the last fetch (2026-10-05T11:04:23Z)