Antarctic ice cores have become a unique and powerful resource for studies of climate change. They contain information on past climate, on forcing factors such as greenhouse gas concentrations, and on numerous other environmental parameters. For recent centuries, sites with high snow accumulation are chosen. They have, for example, provided the only direct evidence that carbon dioxide concentrations have increased by over 30% over the last two centuries. They have provided key datasets for other greenhouse gases, and for other forcings such as solar and volcanic. Over longer timescales, the Vostok ice core has shown how greenhouse gas concentrations and climate have closely tracked one another over the last 400 000 years. Other cores have shown detailed spatial and temporal detail of climate transitions, including the Antarctic response during rapid climate events such as Dansgaard-Oeschger events. The new core from Dome C has extended the range of ice cores back beyond 800 000 years, and even older ice could be obtained in future projects.