The Intergovernmental Panel on Climate Change (IPCC) recognizes that future human behaviors will play a large role in determining how Earth's climate changes over the coming century. We simply don't know how societies and governments will deal with the problem of human emissions of greenhouse gases (GHG) in the years ahead. To account for this type of uncertainty, the IPCC has put forth several possible scenarios of future human GHG emissions. The interactive below provides an overview of the 6 major scenarios used by the IPCC in its attempts to estimate future climate. Use the popup menu in the upper left corner of the interactive to select a scenario. Each listing provides a textual description of the scenario as well as graphs of the CO2 emissions, likely atmospheric CO2 concentrations that would result from that emissions trend, and the range of average global temperature increases that climate models predict from those CO2 levels. Credit: Images courtesy of the IPCC (AR4 WG1 Chapter 10 p. 803 Figure 10.26).