Coral bleaching events are expected to become more frequent and severe in the decades ahead. This page presents climate model projections of severe bleaching conditions (i.e., heat stress >8 Degree Heating Weeks [DHWs]) occurring 2x per decade and 10x per decade (i.e., annual). Coral communities are expected to begin changing when bleaching becomes more frequent than 2x per decade. Corals susceptible to bleaching will be less common and the structural complexity of many coral reefs will decline. These changes will occur more rapidly if/when bleaching events begin to occur annually. The projections for the two bleaching scenarios were produced for emissions scenarios RCP8.5 and RCP4.5, resulting in four (4) projections in total. RCP8.5 is a 'no climate policy' scenario that assumes emissions increase unabated. At the time of writing, in May 2016, emissions concentrations were greater than what RCP8.5 projected for that year. RCP4.5 assumes emissions stabilize just after 2100 due to successful implementation of climate policies that greatly reduce emissions.

These projections are unique in that they have been produced through statistical downscaling so have high resolution (4km) relative to raw climate model data (~1x1°); i.e. relative to the projections available here. The final outputs represent the ensemble average, with 33 climate models (from IPCC CMIP5) used for RCP8.5, and 35 used for RCP4.5. The projection results are available on this page in the form of Google Earth files, map images, and ArcGIS-compatible spatial data. In addition, the projections can be viewed on the United Nations Environment Programme (UNEP) website.

Google Earth (GE) Files

Note: We encourage all viewers to read the Contents Description found in each GE file by selecting the 'About this product' page. This page appears at the top of the file directory structure containing the images (see "My Places" in the left-hand side of the Google Earth interface).

Problems viewing these files are likely to have one of three causes: 1) you need to clear everything from your 'My Places' folder or need to de-select anything saved there; 2) you need to download the most current version of Google Earth; and/or 3) the limitations of your PC or graphics card don't allow for the file to be viewed.

Map Images

Spatial Data

You can view and save the spatial data in ArcMap by opening the layer package below. The file will open automatically and show the four projections' data layers and the reef locations. Coral reef locations shown here at 4km-resolution combine three published global reef-location datasets (ReefBase, Millennium Maps, and Reefs at Risk-Revisited). Other known coral reef locations were added as were any pixels surrounding US-affiliated Pacific Islands with any bottom <30m deep.

The names of the models used in the projections can be found here.

Support for this research was provided by the: NOAA Coral Reef Conservation Program, NOAA Atlantic Oceanographic and Meteorological Laboratory, NOAA Pacific Islands Fisheries Science Center, World Wildlife Fund, UNEP, US Geological Survey Pacific Islands Climate Adaptation Science Center, Pacific Islands Climate Change Cooperative, University of Miami Rosenstiel School of Marine, Atmospheric, and Earth Science, and the European Research Council.

References

van Hooidonk, R., Maynard, J., Tamelander, J. et al. Local-scale projections of coral reef futures and implications of the Paris Agreement. Sci Rep 6, 39666 (2016). https://doi.org/10.1038/srep39666.