WASHINGTON — The Trump administration has recently removed the chief scientist at the National Oceanic and Atmospheric Administration, the nation’s premier scientific agency, installed new political staff who have questioned accepted facts about climate change and imposed stricter controls on communications at the agency.

The moves threaten to stifle a major source of objective United States government information about climate change that underpins federal rules on greenhouse gas emissions and offer an indication of the direction the agency will take if President Trump wins re-election.