The U.S. Senate bill aimed at tackling emissions reductions by imposing new limits on carbon dioxide pollution from factories, utilities and vehicles was introduced Wednesday by Democratic Senator John Kerry and Independent Senator Joseph Lieberman.

The legislation faces tough opposition from Republicans and even some Democrats. There is no guarantee that it will even be debated this year and it is unclear whether a massive oil spill in the Gulf of Mexico will hamper the legislation or prompt a more urgent look at U.S. energy and environmental policy.

At the core of the bill is a goal to cut U.S. carbon emissions by 17 percent by 2020. Click here for the official short summary of the bill.