REPORTER'S TIP SHEET #7

Februay 18, - Week 7
1997 International Year of the Reef

HOW HAS THE EARTH’S CLIMATE CHANGED?
CORAL CORES MAY TELL THE TALE

The earth’s climate has changed in the past and continues to change. A reason for skepticism about global warming and the role of humans in climate change is that accurate measurements of temperature and other climate variables have been made only for the last one hundred years or less. Scientists need to consider conditions over hundreds to thousands of years to understand the potential changes by man from natural variability even at seasonal to decadal time spans.

Even the reliable prediction of climate from one season to a decade in the future requires knowledge of past climate variability and an understanding of how the climate system operates and responds to altered conditions. While climate models help us to replicate past conditions, even these require accurate records of past climate conditions.

Coral reefs have been a fixture of oceans for millions of years and are sensitive to climate changes. As many corals grow, they grow skeletons in bands much as trees grow rings. These bands provide an accurate calendar from which samples can be taken which can be dated to the exact year, season and perhaps month or week that they were deposited.

Chemicals in the calcium carbonate skeleton can reveal invaluable information on ocean temperatures, rainfall/salinity, currents and upwelling. Examination of the skeletons can even reveal chemical contamination of their environment, the timing of their seasonal reproduction and past episodes of severe stress such as coral bleaching. Corals are providing an accurate long-term record of climate change and extending our knowledge of even seasonal climate variability in many remote tropical oceans.

Why do we care about the climate on tropical coral reefs? Much of the world’s climate system is driven by the heat of the tropical oceans, especially the Pacific. The El Niño/Southern Oscillation (ENSO) system has tremendous effects on climate in the Americas and beyond. Recent advances in predicting tropical ocean temperatures have dramatically improved NOAA’s ability to provide seasonal climate forecasts.

The temperature of the central Pacific can influence droughts in the southwestern U.S., floods in the Mississippi and snow in the Pacific Northwest. A strong El Niño can wipe out fisheries in South America. By comparing past records of ocean climate with past records of the effects on land we can better understand natural variability and human influences on the climate system.

Scientific research carried out through various NOAA programs is helping us to understand the past climate changes on coral reefs around the world. Researchers supported by the NOAA Climate and Global Change Program are sampling corals across the Pacific and Indian Oceans to map El Niño events over the past few hundred years. Scientists at the NOAA-cooperative Caribbean Marine Research Center in the Bahamas are examining cores drilled from reefs to estimate changes in temperature and rainfall for the last 500 to perhaps 15,000 years.

Researchers working with the Texas Flower Garden National Marine Sanctuary are using corals to understand linkages between climate in the Pacific and the Gulf of Mexico, while in the Florida Keys National Marine Sanctuary researchers have tried to understand how coastal construction there changed circulation in ways that dramatically altered the environment for corals. Scientists at the National Undersea Research Center in the Florida Keys are using corals to understand how changing UV radiation can influence marine animals.

Through this work and more, scientists are using corals as natural instruments to record climate. While we can start new programs to monitor the earth, it is only through work like this that we can understand our environment from times before we started to take records.

FOR MORE INFORMATION ON THE INTERNATIONAL YEAR OF THE CORAL REEF OR THIS SUBJECT, PLEASE CONTACT MATT STOUT AT: 202-482-6090 OR coralreef@www.rdc.noaa.gov

OR CHECK-OUT THE NOAA CORAL REEF WEBSITES AT:
NOAA's Coral Reef Home Page
Coral Health and Monitoring Program (CHAMP)

OR contact: NOAA Climate and Global Change Program:

Mark Eakin, Program Manager (301) 427-2089 ext. 19 Caribbean Marine Research Center:

Jamie L. Serino, Science Director (561) 471-7552 National Undersea Research Center, Florida Keys:

Steven Miller, Science Director (305) 451-0233 Florida Keys National Marine Sanctuary:

J. Harold Hudson, Regional Biologist (305) 451-1644 Flower Garden Banks National Marine Sanctuary:

Stephen Gittings, Sanctuary Manager (409) 779-2705

Niall Slowey, Research Scientist, Texas A&M University (409) 845-8478

Pacific Coral Paleoclimate Researchers:

Robert B. Dunbar, Rice University (713) 527-4883 Richard G. Fairbanks, Columbia University (914) 365-8499 Latin American Coral Paleoclimate Researchers:

Jorge Cortes, University of Costa Rica (506) 207-5087

Hector Guzman, Smithsonian Tropical Research Institute (507) 228-4022

Effects of UV Light:

Gerard M. Wellington, University of Houston (713) 743-2649

Internet Resources:

Coral Paleoclimate Data are available at:
http://www.ngdc.noaa.gov/paleo/paleo.html

Examine an actual coral core at:
http://seawifs.gsfc.nasa.gov/jason_scripts/coral_subreg.pl

NOAA's Coral Reef Home Page

Other NOAA Resources

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