The Sierra Club, a grassroots environmental organization, has listed the College of William and Mary as one of the five least environmentally friendly American universities.

Interim College President Taylor Reveley’s refusal to sign the American College and University President’s Climate Commitment, which calls for universities to reduce global warming emissions, was a key reason for the title.

George Washington University, Howard University, Texas Tech University and Valdosta State also fail environmentally, according to the Sierra Club. Middlebury College, the University of Colorado — Boulder and the University of Vermont — Burlington are ranked as the most green schools.