NEW : Al Gore warns of ` ` planetary threat , '' announces new presidential campaign . Ex - President Clinton says Gore has warned of dangers for decades . Source : Bush wo n't use prize as springboard to enter 2008 presidential race . White House : President Bush says that Gore , U.N. panel won the prize .
NEW : Al Gore warns of `` planetary emergency , '' announces new ad campaign . Ex-President Clinton says Gore has warned of dangers for decades . Source : Gore wo n't use prize as springboard to enter 2008 presidential race . White House : President Bush pleased that Gore , U.N. panel won peace prize .