U.N. Secretary-General Ban Ki-moon was in Washington on Thursday and asked House of Representatives Speaker Nancy Pelosi for “leadership” in reaching a global pact on climate change when nations gather in Copenhagen later this year to negotiate a treaty to replace the Kyoto Protocol. “I'm here to speak, discuss with you, and ask for your leadership in sealing a deal in Copenhagen in December this year for climate change. I note that you are already in the process of taking national legislation,” told reporters before a closed-door meeting with Pelosi (Democrat from California). Later on Thursday, in a university commencement address in Baltimore, Maryland, Ban said “climate change threatens our way of life” and called it “an existential threat to humankind.” Ban has made climate change his signature issue since taking office two in December 2006. Ban noted in a speech to graduates of Johns Hopkins University that, “Lake Chad, whose waters once supported 30 million people” has “now shrunk to one-tenth the size it was 30 years ago.” The U.N. chief, who will be in Copenhagen on Monday to open the World Business Summit on Climate Change, said the December meeting is a “make or break moment.” “We absolutely must reach an agreement to reduce greenhouse gases and help millions of families adapt to climate change—before our time runs out,” Ban said.