A Greenpeace activist wearing a mask to represent U.S. President Barack Obama takes part in a protest against U.S. policies on climate change in front of the U.S. embassy in Mexico City December 16, 2009. Obama will join more than 120 leaders in Copenhagen on Friday in hopes that he can help seal a political deal on key goals for attacking climate change problems. REUTERS/Eliana Aponte (MEXICO - Tags: CIVIL UNREST ENVIRONMENT POLITICS)