person on the environment for four years, but today, lisa jackson announced she's stepping down as administrator of the environmental protection agency. in a statement, jackson said, "i will leave the e.p.a. confident the ship is sailing in the right direction." jackson's tenure was defined in part by efforts to curb carbon emissions. in 2009, she formally declared greenhouse gases, including carbon dioxide, a threat to public health. that same day, she spoke on "the newshour." >> i join the president in calling for clean energy and climate legislation. and that's because i think having economy-wide legislation sends an unequivocal signal to the private sector that we really mean it, that we're moving towards green energy. >> brown: but a bill to cap greenhouse gases foundered in the democratic-controlled senate and never made it to the president's desk. jackson also pushed a rule to reduce smog, but it faced bitter opposition from republicans and industry over the cost and potential...