Former U.S. President Bill Clinton, left, shares a conversation with Anna Tibaijuka, executive director of the United Nations' Human Settlements Program, known as UN-HABITAT, from Tanzania after an opening ceremony of the 3rd C40 Large Cities Climate Summit Seoul 2009 in Seoul, South Korea, Tuesday, May 19, 2009. AP Photo logo AP Photo 33 months ago

Former U.S. President Bill Clinton, left, shares a conversation with Anna Tibaijuka, executive director of the United Nations' Human Settlements Program, known as UN-HABITAT, from Tanzania after an opening ceremony of the 3rd C40 Large Cities Climate Summit Seoul 2009 in Seoul, South Korea, Tuesday, May 19, 2009.