This chapter is for readers who are not familiar with the basic facts of climate change and climate change policy. The Fourth Assessment Report (AR4) of the Intergovernmental Panel on Climate Change (IPCC), released in 2007, provides comprehensive information. It consists of a Synthesis Report and reports from three working groups: WG I (The Physical Science Basis), WG II (Impacts, Adaptation, and Vulnerability), and WG III (Mitigation of Climate Change). The fifth Assessment Report is due in 2014.

The Science

The scientific basis of climate change is well established, although many quantitative relations are subject to great uncertainty. Briefly, certain gases emitted into the atmosphere change the earth’s energy balance by allowing incoming shortwave solar energy to enter but inhibiting exit of longwave energy. The result is that increases in the concentration of these gases in the atmosphere change the energy balance, resulting in a rise in temperature.