Global Climate Change The Exploratorium
home atmosphere hydrosphere cryosphere biosphere global effects

 Current Coral Bleaching Hot Spots

This map uses sea surface temperatures to forecast the bleaching of coral reefs. It is updated twice weekly—on Tuesdays and Saturdays. On the site where this map is featured, you can click on any area of the map to see a close-up view of that area.

Coral reefs are built by colonies of coral polyps, tiny animals that live in a symbiotic relationship with algae. Under environmental stress, coral polyps may expel their algae and lose their color, a process known as coral bleaching. Coral bleaching may lead to the death of the coral polyps—and the reef itself—and degradation of the ecosystem that the reef supports.

Coral bleaching has increased over the last two decades. Most of the major bleaching events of the 1980s and 1990s have been linked to elevated water temperatures. However, warmer water alone may not cause bleaching events. Other other factors—such as low winds and very sunny days—may amplify the thermal stress. A variety of other environmental stresses—such as disease, excess shade, increased levels of ultraviolet radiation, sedimentation, pollution, and salinity changes—may also play a role.

In an effort to determine all the factors associated with coral bleaching, NOAA’s Coral Reef Team asks coral reef scientists, divers, and others to report coral bleaching and the conditions under which it occurs.

 glossary glossary terms  

Click for definitions of words used on this page:

coral bleaching
remote sensing

View the full, printable version of the glossary.

Current Coral Bleaching Hot Spots
Current Coral Bleaching Hot Spots

Click on regions in the world map to view close-up images.

Current Coral Bleaching Hot Spots - Colored areas on this map show where coral is experiencing stress from elevated water temperatures. The colors represent the difference between the sea surface temperature (in degrees Celsius) and the sea surface temperature identified as the coral bleaching threshold. Only positive differences are highlighted. Source:National Oceanic and Atmospheric Administration (NOAA)
ORA/OSDPD Coral Reef Team

 questions about the data  

question Do scientists have anything good to say about coral bleaching?

email Email your own questions about these data sets. 

 research connection  

This map highlights temperatures that are higher than the expected maximum. But what’s the expected maximum? In this case, it’s the maximum monthly mean sea surface temperature, calculated from sea surface temperatures measured by satellite from 1984 to 1993—excluding the years 1991 to 1992. (Those years were excluded because they followed the eruption of Mount Pinatubo. The aerosols from that eruption reflected sunlight and had a cooling effect on the climate.)

 related sites  

Coral Reef Watch Program - Information on coral bleaching and links to related sites.

Silent Sentinels: The Future of Coral - Web site and transcript from a documentary by the Australian Broadcasting Corporation, discussing the connection between coral and water temperature.

Reef Research/Bleaching - A discussion of the factors involved in coral bleaching.

Causes of Coral Bleaching - A scientist reviews the scientific literature dealing with coral bleaching events and disputes that elevated seawater temperatures are the primary cause of coral bleaching.

Assessing the Future of Earth's Coral Reefs - A scientist notes that the scientific community is not united on the subject of atmospheric CO2 enrichment and coral reef health.

home | atmosphere | hydrosphere | cryosphere | biosphere | global effects

about this site - © 2002 The Exploratorium