The Obama administration's tough targets for cutting greenhouse gas emissions could hit Americans right in the pocketbook.

Harvard researchers estimate that those targets could lead to gasoline costing as much as $7 a gallon.

The researchers' models factored in an economy-wide carbon dioxide tax starting at $30 a ton in 2010 and increasing to $60 a ton in 2030. Tax credits for electric and hybrid vehicles and taxes on fuel were also factors.

"Tax credits don't address how much people use their cars," said Ross Morrow, one of the report's authors. "In reverse, they can make people drive more."

The New York Times reports the researchers tried to find ways to get America to cut its greenhouse gases. They found that increased taxes on gas is the best way to get people to drive less and cut the carbon dioxide emissions from cars and other vehicles.

Researchers believe that vehicle miles traveled will increase by more than 30 percent between 2010 and 2030, unless lawmakers increase fuel taxes.