The production of greenhouse gases due to anthropogenic activities may have begun to change the global climate. The global carbon cycle plays a significant role in projected climate change. However, considerable uncertainty exists regarding pools and flux in the global cycle. Given the authors present understanding of current global carbon sources and sinks, feedbacks from the biosphere are likely to influence the process of climate change. Opportunities may exist to manage the biosphere and reduce the accumulation of greenhouse gases in the atmosphere. The four chapters in this section survey the role of the global carbon cycle in projected climate change.