evidence: Scott Pruitt, Donald Trump’s head of the US Environmental Protection Agency, has dismissed a basic scientific understanding of climate change by denying that carbon dioxide emissions are a primary cause of global warming. [...] "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, so no, I would not agree that it’s a primary contributor to the global warming that we see," he told CNBC. [...] This stance puts Pruitt at odds with his own agency, which states on its website that carbon dioxide is the "primary greenhouse gas that is contributing to recent climate change". This finding is backed by Nasa, which calls CO2 "the most important long-lived ‘forcing’ of climate change".