Environmental records from coral skeletons: A decade of novel insights and innovation

Hundreds of coral paleoclimate records have been developed over the past several decades, significantly extending the instrumental record and improving our understanding of tropical climate variability and change in otherwise data‐poor regions. Coral “proxy” records measure the change in skeletal geochemistry or growth as a function of ocean conditions at the time of calcification. Over the past decade (since 2010), new syntheses have identified coherent patterns of warming and variability that are unique within the paleo record (albeit not yet unprecedented). In turn, ocean warming and acidification have had a detrimental impact on coral growth, with reduced extension and increased stress banding. Methodological advances have constrained uncertainties and improved our understanding of the processes by which climate information is archived in coral skeletons. Models that describe these processes have been developed to facilitate proxy‐model comparisons, identify sources of uncertainties, and provide a benchmark upon which forced changes may be detected within a highly variable climate system. Finally, several innovative new proxies have expanded the climate and environmental information that may be obtained from corals, including: seawater pH, aragonite saturation, anthropogenic nitrogen, runoff, and trade winds. Further extending established and novel proxies should remain a priority, along with seawater monitoring and density measurements with which to screen and calibrate these records. As this critical climate archive is increasingly threatened by warming and ocean acidification, the community must work closely together to collect this invaluable climate data in an ecologically and culturally sensitive manner, before it is too late.