Good evening and thanks for joining us.

President Obama is proposing the toughest regulations in US history to combat climate change.

In a video previewing tomorrow 's announcement, the President says climate change is not an opinion,

but a fact and a threat.

He calls power plants the biggest domestic source of polluting emissions that contribute to global warming.

The most significant rule would require existing power plants to cut emissions from 2005 levels by 32 % by 2030.

Other rules would limit construction of new coal - burning plants

and require more use of clean energy sources, like wind and solar.

We limit the amount of toxic chemicals like mercury and sulfur and arsenic in our air and water,

and we're better off for it.

But existing power plants can still dump unlimited amounts of harmful carbon pollution into the air we breathe.

For the sake of our kids, for the health and safety of all Americans, that's about to change.

Every state would be required to give the Environmental Protection Agency its plan for curbing emissions,

but the rules face opposition from Congressional Republicans and lawsuits from the energy industry and coal power states.