A subsidiary of Atlanta-based Southern Company is pouring billions of dollars into construction of a coal burning power plant that will emit less carbon dioxide.

It's a response to looming federal limits on carbon emissions as regulators try to curtail global warming.

The projected cost of Plant Ratcliffe in Mississippi’s Kemper County is at least $2.8 billion. That’s almost half a billion dollars above original expectations and some estimates say it will go higher.

Legal challenges brought by the Sierra Club have led regulators to block the company from billing customers for the costs so far, although Southern Company subsidiary Mississippi Power Co. got closer to that goal with a favorable lower court ruling earlier this month.

Southern Company CEO Thomas Fanning stands by the plant. He says Southern's own technology will mitigate its environmental impact and the need to exploit coal as a hedge against uncertainties in the future cost of natural gas, which is currently cheap and abundant.

The company promises completion in May 2014, but some engineers monitoring construction for state regulators warn the cost could reach $3.1 billion, and completion isn't likely until November 2014 at the earliest.

Southern Company is also is at work on two additional nuclear reactors in Georgia at Plant Vogtle southeast of Augusta.

Tags: environment, Southern Company, Plant Vogtle, power plant, Plant Ratcliffe