Thermal History (1985-2020)
(Version 3.1.2, released September 15, 2021)

Stress Frequency
Stress Frequency
Stress Onset
Stress Onset
SST Variability
SST Variability
SST Trend
SST Trend
Annual History
Annual History

(Click on the maps to access the corresponding products.)

Download data (netCDF):    FTP site
Stress Frequency (261Mb) | Stress Onset (421Mb) | SST Variability (261Mb) | SST Trend (141Mb)
Climatology (621Mb) | Annual History (7.3Gb)

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Product Description

Climate change threatens even the best-protected and most-remote coral reef ecosystems. Management in the face of climate change must incorporate how various factors (e.g., benthic structure, currents and local upwelling, connectivity, herbivore abundance, thermal history) affect coral and reef ecosystem resilience. Research over the last decade indicates that thermal history is among the most important factors influencing coral reef resilience.

With support from the NOAA Coral Reef Conservation Program, Coral Reef Watch (CRW) developed a variety of Thermal History metrics for coral reef management, initially released in July 2014. In the current Version 3.1.2 (v3.1.2, released September 2021), several Sea Surface Temperature (SST) metrics are calculated for reef-containing locations and adjacent waters and are arranged into six themes: Stress Frequency, Stress Onset, SST Variability, SST Trend, Climatology, and Annual History.

The v3.1.2 metrics were derived from CRW's v3.1 daily global 5km (1/20°) CoralTemp satellite SST data product, for the period 1985-2020. Source data for CoralTemp are the NOAA/National Environmental Satellite, Data, and Information Service (NESDIS) operational near real-time Daily Global 5km Geostationary-Polar-orbiting (Geo-Polar) Blended Night-only SST Analysis, from October 2016 to present; the NOAA/NESDIS Daily Global 5km Geo-Polar Blended Night-only SST Reanalysis (a reprocessed dataset), from November 2002 to October 2016; and the Daily Global 5km Night-only SST Reanalysis produced by the United Kingdom Met Office, on the Operational SST and Sea Ice Analysis (OSTIA) system, from January 1985 to November 2002.

Evolution of CRW's Thermal History Product Suite


Thermal History Product Metrics (v3.1.2)
Images NetCDF
Stress Frequency Metrics
  • Number of Heat Stress Events (Degree Heating Weeks [DHW]>0)
  • Number of Significant Bleaching-level Heat Stress Events (DHW≥4)
  • Number of Severe Bleaching-level Heat Stress Events (DHW≥8)
  • Time between Heat Stress Events (DHW>0)
  • Time between Significant Bleaching-level Heat Stress Events (DHW≥4)
  • Time between Severe Bleaching-level Heat Stress Events (DHW≥8)
Stress Onset Metrics
  • Mean Onset - Significant Bleaching-level Heat Stress
  • Earliest Onset - Significant Bleaching-level Heat Stress
  • Onset Variability - Significant Bleaching-level Heat Stress
SST Variability Metrics
  • Warm Season Variability
  • Warmest Month Variability
  • Average Warm Season Variability
  • Average Warmest Month Variability
  • Annual Variability
  • Average Within-year Variability
SST Trend Metrics
  • Warm Season Trend
  • Annual Trend
  • Warmest Month Trend
Climatology Metrics
  • Warmest Month
  • Climatological Temperature Range
  • Coolest Month
  • Monthly Climatology
Annual History Metrics
  • Annual Maximum SST
  • Annual Maximum SST Anomaly
  • Annual Maximum DHW
  • Within-year SST Average
  • Within-year SST Variability