WASHINGTON – Climate change suddenly is a hot topic again. The issue is resurfacing in talks about a once radical idea: a possible carbon tax.

On Tuesday, a conservative think tank held discussions about it while a more liberal think tank released a paper on it. And the Congressional Budget Office issued a 19-page report on the different ways to make a carbon tax less burdensome on lower income people. A carbon tax works by making people pay more for using fossil fuels: coal, oil, and gas that produce heat-trapping carbon dioxide.

The idea was considered so radical that in 2009 when President Barack Obama tried to pass a bill on global warming, he instead opted for the more moderate approach of capping power plant emissions and trading credits that allowed utilities to pollute more. That idea, after passing the House, stalled in the Senate in 2010 and has been considered dead since.