Ken McQueen was criticized for allowing a controversial oil and gas company to double its well density in northwest New Mexico when he was a state official there.
The hearing revealed a subtle shift on the Republican side, with younger members acknowledging that scientific research points to human-driven global warming.
He walked it back after a sharp reaction from scientists, but it's a stark example of Trump efforts to undermine federal work on global warming risks, advocates say.
A pivotal EPA study provided the rationale for exemptions that helped unleash the fracking boom. The science was suppressed to protect industry interests.
Documents show Pruitt targeted information about the Clean Power Plan while preparing to rescind it. Environment groups are now calling for him to recuse himself.