Environmental groups had sued, saying the polar bear needed more protection under the Endangered Species Act. The state of Alaska, under the leadership of then-Gov. Sarah Palin, and hunting groups argued that the listing was unnecessary. They say the bear is protected by other laws and that the scientific case is shaky when it comes to predicting global warming’s toll on the mammal.

In a 116-page opinion, Sullivan dismissed both arguments as “nothing more than competing views about policy and science.”

“According to some plaintiffs, mainstream climate science shows that the polar bear is already irretrievably headed toward extinction throughout its range. According to others, climate science is too uncertain to support any reliable predictions about the future of polar bears,” Sullivan wrote. “This Court is not empowered to choose among these competing views. That is particularly true where, as here, the agency is operating at the frontiers of science.”