What is the environmental, economic, and social benefits and costs of policies based on each of the two viewpoints: "It is extremely likely that human influence has been the dominant cause of the observed warming since the mid-20th century." (IPCC 5th Assessment report) "There are no experimental data to support the hypothesis that increases in human hydrocarbon use or in atmospheric carbon dioxide and other greenhouse gases are causing or can be expected to cause unfavorable changes in global temperatures, weather, or landscape." (Petition Project Report)