Xinhua: UN Secretary-General Ban Ki-moon urged on Monday developed countries to take the lead in a global drive to tackle the challenges of climate change. "Developed countries need to take a clear lead, but success is possible only if all countries act," Ban said at the opening of a two-day General Assembly debate on climate change. He said the Bali conference last December has set a target for the world to reach an agreement by the end of 2009 on action to counter the …