Current Research: My research interests encompass various aspects of climate change and climate variability, particularly physical and biogeochemical processes occurring at the global and continental spatial scales. I look into these problems using mainly climate models but also employ observations. I have used models to address questions on a broad range of subjects from paleoclimate to climate policy, with a concentration on carbon cycle modeling. I am also interested in using paleoclimatic data to constrain archaeological and biogeographic theories. Some examples of scientific questions I have attempted to answer include: What will climate be like 5000 years from now if we burn all available fossil fuel reserves? Will large scale planting of trees worldwide cool or warm the climate? Could ocean acidification have caused the global extinction event 250 million years ago? Could the Polynesian islands have been discovered by accidental drift voyages? Could the transoceanic crossings from Africa have introduced the bottle gourd into the Americas?