Want, as long as we don't take real bold action right now, in reducing the emissions at the source, then it doesn't really mean anything. >> reporter: one big remaining question here, of course, is how to hold the international community and the u.s. accountable to reaching these new targets. something that the white house says they hope will come out of a new summit this fall in glasgow. david? >> all right, mary bruce live at the white house tonight. mary, thank you. and with the president and this summit with world leaders, tonight climate and its role in what we've witnessed on the south...