Warm Forecast for Coral Reefs

Dataset information

Corals are very sensitive to water that is too warm—even temperatures that are just 1–2°C above the highest average summertime temperature. If corals bathe in water above this critical threshold for just four weeks (or at higher temperatures for even shorter durations), the accumulated heat stress can induce coral bleaching. Bleaching is a condition where coral polyps expel the algae that they rely on for nutrition through photosynthesis. While bleached coral can recover, it is susceptible to disease and can remain weakened for years, or even die.

NOAA’s Coral Reef Watch program documents accumulated heat stress to corals—a measure called degree heating weeks—based on sea-surface temperature measurements taken every three days from the AVHRR sensor on NOAA's polar-orbiting satellites. This visualization begins with a time series of weekly averages of degree heating weeks data for 2013. The annual images of heat stress from 2010 and 2013 are composites of the maximum values of degree heating weeks in reef areas over the given year. Coral reef locations are from the World Resource Institute’s Reefs at Risk Revisited report.

The last map in the visualization is from a 2014 study that used climate models to project when and where corals may experience severe bleaching every year, or eight or more degree heating weeks annually. The map is an average of the projections from a number of models. It represents a “business as usual” scenario for future greenhouse gas concentrations (IPCC RCP 8.5), in which only modest future progress is made to reduce energy use and emissions. [Van Hooidonk, R. J., J. A. Maynard, D. Manzello, and S. Planes. 2014. Opposite latitudinal gradients in projected ocean acidification and bleaching impacts on coral reefs. Global Change Biology: 103–112.]

Google+ Hangout

On April 9, 2014, AMNH Science Bulletins hosted a Google+ Hangout about corals and climate with two coral reef specialists from the National Oceanic and Atmospheric Administration: Mark Eakin, coordinator of NOAA’s Coral Reef Watch program, and Ruben van Hooidonk, assistant scientist with NOAA’s Atlantic Oceanographic and Meteorological Laboratory and the University of Miami.

Watch the Hangout recording on YouTube to learn how corals are responding to climate change and how scientists monitor reefs and make projections about their future. The Hangout offers strategies for interpreting the data visualization Warm Forecast for Coral Reefs and the set of coral bleaching forecasts for Google Earth that accompany the visualization.

This visualization and professional development training is supported by NOAA.

Coral Bleaching Forecasts for Google Earth

Scientists predict that warming ocean temperatures will cause more frequent episodes of coral bleaching in the future. But how warm temperatures become—and thus, how frequently corals will bleach—depends on future emissions of greenhouse gases. In this Google Earth file, a companion to the video Warm Forecast for Coral Reefs, explore five forecasts of coral bleaching based on various emissions scenarios (called RCPs) outlined by the 2013 IPCC report.

RCP 8.5 is a "business as usual" scenario, in which only modest future progress is made to reduce emissions. RCP 6 shows a linear reduction in future emissions, while RCP 2.6 and 4.5 show stabilization later in the century—each is more of an emissions "arc" than an incline. For each of these scenarios, the rate of change in emissions would affect how soon corals in different locations will experience frequent bleaching.

If corals experience severe bleaching about twice in one decade—which is about how often they currently bleach—they can recover. But if bleaching occurs on an annual basis, corals are not likely to be able to recover and survive. This Google Earth file includes forecasts for both twice-a-decade and annual bleaching for the RCP 8.5 scenario. For the other three scenarios, it only includes a projection of annual bleaching. For more information, click on "About these images" in the Google Earth file.

Credits

Special thanks to Dan Pisut of the NOAA Environmental Visualization Laboratory; Mark Eakin of NOAA Coral Reef Watch at the National Environmental Satellite, Data, and Information Service; and Ruben van Hooidonk of NOAA’s Atlantic Oceanographic and Meteorological Laboratory and the University of Miami.

This visualization was produced by the American Museum of Natural History under award NA10SEC0080014 from the National Oceanic and Atmospheric Administration (NOAA), U.S. Department of Commerce. The statements, findings, conclusions, and recommendations are those of the author(s) and do not necessarily reflect the views of NOAA or the U.S. Department of Commerce.

Related Links

General information

• NOAA Coral Reef Watch Tutorial
  http://coralreefwatch.noaa.gov/satellite/education/tutorial/welcome.php

• NOAA: New study suggests coral reefs may be able to adapt to moderate climate change
  www.noaanews.noaa.gov/stories2013/20131029_coral.html

• Science Daily: New maps depict potential worldwide coral bleaching by 2056
  www.sciencedaily.com/releases/2013/02/130225122045.htm
• World Resources Institute: Reefs at Risk Revisited
  www.wri.org/publication/reefs-at-risk-revisited

Data Sources

• NOAA Coral Reef Watch (Accessed through NOAA View)
  http://www.nnvl.noaa.gov/view/#CDHW
• Van Hooidonk, R. J., J. A. Maynard, D. Manzello, and S. Planes. 2014. Opposite latitudinal gradients in projected ocean acidification and bleaching impacts on coral reefs. Global Change Biology: 103–112.

Collaborators

• NOAA Environmental Visualization Laboratory
  http://www.nnvl.noaa.gov/

• NOAA Coral Reef Watch
  www.coralreefwatch.noaa.gov/