evidence: When asked during an interview on CNBC on Thursday if he believes carbon dioxide is the main "control knob" warming the planet, Pruitt said "measuring with precision human activity on the climate is something very challenging to do and there's tremendous disagreement about the degree of impact." "I would not agree that it's a primary contributor to the global warming that we see," Pruitt said, speaking from an energy conference in Houston. "But we don't know that yet." [...] In 2007, the Supreme Court ruled that carbon dioxide should be considered an "air pollutant" under the Clean Air Act. Using that authority, President Obama's EPA determined in 2009 that carbon dioxide and other greenhouse gases, as contributors to global warming, are harmful to human health and should be regulated.