Democratic Senator Barbara Boxer and Independent Bernie Sanders introduced legislation on Thursday to curb emissions of carbon dioxide, levying a $20 tax for each ton of this climate-warming substance over a set limit. That limit would be 5.6 percent annually over a 10-year period, raising up to $1.2 trillion in revenue over 10 years that would largely be returned consumers, the bill's sponsors said.
Congress has failed to pass a carbon-curbing law, most recently in 2010, and prospects for passage this year are bleak.
The leaders of a congressional climate change task force applauded the GAO listing as a possible prod to Congress to take action.
California Representative Henry Waxman, who co-chairs the task force and is the ranking Democrat on the House Energy and Commerce Committee, called it a "huge development."
"Congress can't ignore an issue that its own auditors say is a top risk to taxpayers," Waxman said in a statement. "The costs of inaction on climate change will be much higher than the costs of responsible action."