Understanding the nature and causes of past global change is a key to
understanding what may happen in the future. The discovery, nearly 25
years ago, of annual density bands in skeletons of long-lived, massive
corals promised high-resolution proxy climate records for tropical oc
eans. The tropics are regions of major importance to the global climat
e system and they are poorly represented by high-resolution proxy clim
ate records such as tree rings, ice cores and historical documents. In
this review we examine the principles and procedures underlying routi
ne recovery and interpretation of information from proxy environmental
recorders. We summarize an extensive literature which indicates that
coral skeletons are excellent archives for considerable and diverse en
vironmental information. We show that this potential has not been full
y realized, largely because corals seemed to yield inconsistent, somet
imes conflicting, information. We discuss ways in which much of this c
onfusion is resolved by new understanding of coral skeletal growth mec
hanisms. We also examine several records which indicate that corals ca
n meet requirements for reconstruction of useful, reliable environment
al information.