CQPolitics.com: As a House panel prepares to mark up global warming legislation, an early EPA analysis concluded that the cost could be less than expected — partly because of the struggling economy. Edward J. Markey, D-Mass., chairman of the Energy and Commerce Subcommittee on Energy and the Environment, is holding hearings this week — coinciding with Earth Day on Wednesday — on draft legislation that would establish a “cap and trade” system for greenhouse gases and promote the use of clean …