Yvo de Boer , executive secretary of the U.N . Copenhagen chief Clinton : ` ` We have a chance , a real chance , here and now '' Ban Ki-moon urges poor nations to help as U.N. climate summit heads into home stretch . World leaders begin arriving for `` high-level '' negotiations in Monday of summit .
Copenhagen chief Clinton : `` We have a chance , a real chance , here and now '' Ban Ki-moon urges poor nations to help as U.N. climate summit heads into home stretch . World leaders begin arriving for `` high-level '' negotiations in Monday of summit .