Senate Republicans are questioning the Obama administration about reports that U.S. officials tried to suppress the 15-year global warming hiatus in the United Nations’ climate report.

The Associated Press reported in September that the Obama administration, along with several European nations, lobbied the Intergovernmental Panel on Climate Change to omit or downplay data showing that global warming stopped in 1998.

In response, Republican senators have sent a letter to Environmental Protection Agency Administrator Gina McCarthy, questioning her knowledge of these international lobbying efforts.