Chappell has made a major contribution toward understanding late Quaternary sea level changes, based on raised coral reefs in Papua New Guinea and elsewhere. Through use of stable isotopes and radiometric dating, links between sea level, global ice volume, and past climates have been established, contributing substantially to the astronomical theory of ice ages. Coupling this work with research on processes and late Quaternary history of coasts, reefs, and estuarine lowlands, Chappell is now mainly concerned with high resolution analysis of lowland environmental histories, and with developing predictive models of effects of future sea-level changes on these important environments.