Understanding the nature and causes of climate variability and change in the tropical oceans—the heat engine of the global climate system—is limited by the relatively short length of instrumental records. Certain massive reef-building corals contain a wealth of historical proxy climate and environmental information locked in their calcium carbonate skeletons. This information is available from living corals that can be up to several hundred years old and from fossil corals, often well preserved after death, for well-dated windows of the more distant past. Continuous, high-resolution (annual to seasonal) information from such corals is provided by a range of measures that include growth characteristics which can document coral responses to unusual environmental conditions and various geochemical tracers whose incorporation into the skeleton is mediated by ambient seawater characteristics. The stable oxygen isotope ratio, δ18O, has been the most commonly measured coral environmental tracer and, although reflecting both sea surface temperature and seawater salinity, long records of this variable are providing new insights into interannual (e.g., El Niño-Southern Oscillation), decadal, and longer time-scale variability in the tropical oceans—information not accessible from the instrumental records—which complements other sources of high-resolution proxy climate information (e.g., tree rings, ice cores, documentary records). The contribution of proxy climate records in corals to the global picture of past climates is being enhanced through efforts to reduce the various sources of uncertainty that can confound the interpretation of any source of proxy climate information. Copyright © 2010 John Wiley & Sons, Ltd.
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