In May 2018, the Department of Energy's Office of Energy Efficiency and Renewable Energy circulated a list of "tier 1" topics on which researchers could not publish unless they had first obtained approval from political appointees. The list included issues relating to electric grid reliability, and "projections of entire energy sectors," such as fossil fuels and renewable energy.
Update:
On October 26, 2020, Grist and Investigate West reported widespread political interference in scientific research on "tier 1" issues. According to the report, "[p]re-publication review of Tier 1 reports enabled the Energy Department's top political appointees to scrutinize scientists' findings and demand changes or prevent their release. Such interference has occurred regularly since, according to emails, documents, and interviews obtained or conducted by InvestigateWest." The report quoted one email, from May 2019, in which the then acting director of DOE's Wind Energy Technology's Office complained that there was "a backlog of reports in Tier One situation."