CHEYENNE, Wyo. -- Wyoming Gov. Matt Mead is asking the White House to not evaluate the effects of greenhouse gases that would be emitted by exporting U.S. coal and burning it overseas.Wyoming is the nation's leading coal-producing state and state officials are concerned about falling domestic demand for coal as a result of global warming concerns. State officials are pushing to secure ports in the Northwest to allow coal exports to Asia.In a joint letter last month, Washington Gov. Jay Inslee and Oregon Gov. John Kitzhaber asked the federal government to examine the consequences on global air quality of shipping up to 140 million tons of coal a year from the Powder River Basin in Wyoming and Montana.