Tar sands oil is the dirtiest fuel on Earth. Because producing it consumes so much energy, a gallon of tar sands crude generates 17 percent more carbon pollution than conventional crude oil.

The more people learn about the proposed Keystone XL tar sands pipeline, the worse it looks.

I have visited people whose health has been endangered by tar sands oil. I have watched neighbors struggle to recover from Superstorm Sandy. I have seen solar panels and wind turbines become an increasingly familiar part of the landscape.

Countries have made impressive pledges to cut carbon pollution, but we have to ensure these promises become actions.

Putting a tax on carbon could be an effective approach for curbing global warming pollution.

Pollution from oil and gas development, toxic runoff, and miles and miles of plastic trash foul the waters and threaten marine life.