In the year 2000, the American Geological Institute (AGI) began developing its EarthInquiry activity series. Since that time, seven full-length activities have been released. Each EarthInquiry activity enables introductory college students to interact with real-time and archived geoscience data. EarthInquiry addresses some of the most commonly discussed topics in introductory geoscience course work. Each activity has its own workbook, printed by W.H. Freeman and Company that contains a code, allowing students access to the EarthInquiry web site. The EarthInquiry web site, maintained by AGI, provides students with detailed instructions on how to access, analyze, and interpret the data collected in each activity. The web site also supplies supplementary information, glossary terms, and web-based tools to assist with data analysis. In the Long-term Climate Change activity, students begin to understand some of the fundamental challenges faced by climate scientists trying to distinguish naturally occurring climate variability from potentially human-induced climate change. The Vostok ice-core record of two gases, carbon dioxide and methane, is used to introduce students to natural cycles of variability in the atmospheric system. In an effort to understand the cause(s) of these natural cycles, students superimpose the Milankovitch cycles, as calculated by Berger and Loutre (1991), over the Vostok gas records. As students work through the investigation, they develop a deeper understanding of how natural variability in the Earth's insolation can influence cyclic changes in the presence of gases, ice volume, and even temperature. In the online Assessment activity, students compare the current carbon dioxide and methane concentrations to those preserved in the Vostok record, and consider what these modern concentrations might say about a human impact on climate change.