The U.S. Department of the Interior designated polar bears as threatened this week, in a much-watched decision and protracted legal tussle.

This arresting image shows how little mature ice remains in the Arctic region.Interior Secretary Dirk Kempthorne said the listing is based on the best available science, which shows that loss of sea ice threatens and will likely continue to threaten polar bear habitat. Although the population of bears has grown from a low of about 12,000 in the late 1960s to approximately 25,000 today, computer modeling projects a significant population decline by the year 2050 because of rapidly receding ice.

But, according to the New York Times, Kempthorne made it clear that it would be “wholly inappropriate” to use the listing as a tool to reduce greenhouse gases.

"Listing the polar bear as threatened can reduce avoidable losses of polar bears," he said. "But it should not open the door to use the ESA to regulate greenhouse gas emissions from automobiles, power plants, and other sources."

Three organizations -- Greenpeace, the Natural Resources Defense Council and the Center for Biological Diversity -- filed suit three years to force a listing of the polar bear. At least one of those groups has explicitly pursued the listing as an avenue to curb sources of greenhouse gases.