Global Coral Bleaching Event Overview

January 2023 saw the start of the fourth global coral bleaching event (GCBE4). It is the most widespread and fastest coral bleaching event yet seen. As to the National Oceanic and Atmospheric Administration (NOAA), heat stress has affected 99.9% of the Atlantic Ocean's coral reefs. Over 11% more bleaching has occurred this time than in 2014–2017.

How it Compares to Coral Bleaching

• Compared to past events, GCBE4 has affected around 77% of global reef areas in only 20 months.
• Full bleaching has been identified in 74 countries since February 2023 with mass coral bleaching evident in Palau, Guam and Israel.
• Variations in climate like the El Niño and La Niña phases, have caused bleaching making reefs susceptible to damage.
• A coral reef in the Atlantic has been exposed to bleaching-level heat stress, for nearly two years in places in the Caribbean.
• Future effects of GCBE4 are delayed, and assessments may take years.
• Coral mortality can initiate within days of marine heatwave onset, and full impact may not be observed for one to two years.
• The background information about coral mortality includes white-band disease in the US Virgin Islands during 2005 and current mortality rates in corals of the Mexican Pacific.
• Coral reefs in danger (Scientists, UN seek emergency session at COP16 on coral reefs)