Scott Pruitt is right: the US Environment Protection Agency (EPA) never seriously considered the science used in its 2009 GHG/CO₂ endangerment finding. That is the conclusion of  Dr Alan Carlin. You can read his thorough and well argued narrative here on his excellent blog. Alan is  a sceptical former Sierra Club activist and USEPA senior analyst, so he is well qualified to give his opinion.

Here is an excerpt from an interview with EPA Administrator, Scott Pruitt: “So it really draws down into [this] question: Did this Agency engage in a robust, meaningful discussion, with respect to the Endangerment that CO₂ poses to this Country? And I think by any definition about process they didn’t.” —Scott Pruitt in interview with Justin Worland of Time Magazine, as reported on October 20, 2017 and transcribed here.