Zinke has shifted on the issue of climate change over time.[50] In 2010, while in the state Senate, Zinke was one of nearly 1,200 state legislators who signed a letter to President Obama and Congress calling for "comprehensive clean energy jobs and climate change legislation."[50] Since 2010, however, Zinke has repeatedly expressed doubt about anthropogenic climate change; in an October 2014 debate, Zinke stated: "it's not a hoax, but it’s not proven science either."[50] During Senate confirmation hearings on his nomination as Interior Secretary, Zinke said that humans "influence" climate change, but did not acknowledge the scientific consensus that human activity is the dominant cause of climate change.[51]