ou’ve probably already heard about the various threats caused by global warming: melting glaciers, extreme weather disturbances and endangering the habitat of the polar bear. Tomorrow, the Natural Resources Defense Council will add another concern to the list: the endangered winter sports fan. As the NRDC put it in a press release yesterday: Some of the top names in winter sports are going to the U.S. Capitol Thursday to ask lawmakers to stop efforts in Congress to block the Environmental Protection Agency’s ability to reduce greenhouse gas emissions.