State-level policies to control greenhouse gas emissions are essential for mitigating the economic, health, and environmental threats posed by global climate change. States play a crucial role in helping the US as a whole to meet the national pledge to reduce greenhouse gas emissions. However, the circumstances surrounding climate change creates a complicated and politically volatile situation for policy-makers who must deal with complex and uncertain scientific issues and develop policies that potentially affect multiple economic sectors, including energy, transportation, agriculture, industry, and forestry. This guidance document is intended to help states evaluate these complex issue and develop response strategies that address their distinct situations. EPA's objective is to assist each state in formulating a realistic State Action Plan for addressing greenhouse gas emissions.