evidence: The head of the U.S. Environmental Protection Agency, Scott Pruitt, said Thursday morning that he doesn’t think carbon dioxide is "a primary contributor" to climate change. "I think that measuring with precision human activity on the climate is something very challenging to do and there’s tremendous disagreement about the degree of impact," Pruitt said on CNBC’s show Squawk Box. "So no, I would not agree that it’s a primary contributor to the global warming that we see. But we don’t know that yet … we need to continue the debate and continue the review and the analysis." Pruitt’s statement is at odds with the vast scientific research on climate change, including the consensus of U.S. scientific agencies such as NASA and the National Oceanic and Atmospheric Administration (NOAA), as well as the EPA itself. Contrary to Pruitt’s statement, CO2 is a known greenhouse gas and scientists have been precisely measuring carbon dioxide levels in the atmosphere at the Mauna Loa Observatory in Hawaii since the 1950s. Pre-industrial CO2 levels were about 280 parts per million (ppm) and have soared from about 315 ppm in 1960 to 407 today.