On January 31, 2018, EPA Acting Administrator Andrew Wheeler appointed eight new members to the SAB. One of the new appointees — Dr. John Christy — is a professor at the University of Alabama in Huntsville who has long questioned established climate science. Following announcement of his appointment, Dr. Christy said he would use his position on the SAB to challenge the findings of climate models, which he has long asserted do not accurately reflect climate variability. Dr. Christy also suggested that he would challenge scientific studies demonstrating that greenhouse gas emissions are the primary cause of climate change, stating that there is “tremendous uncertaint[y] . . . on this issue” and that “[t]he overconfidence we have on the climate issue in the climate community is incredibly large and we need to pull back on that.” He went on to question the appropriateness of regulations limiting greenhouse gas emissions, claiming that the endangerment finding (which provides the basis for such regulations) “doesn’t stand on the best science that we have out there.”

On July 15, 2019 the Government Accountability Office released an audit report in which it found that the EPA bypassed normal procedures in appointing members to the Scientific Advisory Board and the Clean Air Scientific Advisory Committee. The report showed that the Trump Administration rigged the boards to favor candidates with industry connections. In a written response, the EPA strongly denied any suggestion of impropriety.