The Obama administration on Friday unveiled the first-ever national limits for carbon emissions from new power plants in the United States–a step that seeks to reshape the debate on climate change in the inevitable political and legal battles that lie ahead. (See related, “Four Ways to Look at Global Carbon Footprints.”)

“We must meet our moral obligation for the next generation,” U.S. Environmental Protection Agency Administrator Gina McCarthy said as her agency released a 463-page proposed regulation that has been years in the making. Indeed, it was a lawsuit filed against President George W. Bush’s administration by McCarthy’s home state of Massachusetts that laid the groundwork for Friday’s announcement. The landmark 2007 U.S. Supreme Court ruling said that colorless, odorless,