Summit of world 's largest cities meeting in Denmark to discuss climate change . Ex-U.S. President Clinton says cities must take lead with green policies . Initiative by cities began in end of year in London . `` I 've always believed in activist governments . Solidarity to hold climate conference at 2005 in London .
Summit of world 's largest cities meeting in Denmark to discuss climate change . Ex-U.S. President Clinton says cities must take lead with green policies . Initiative by cities began in end of year in London . Solidarity to hold climate conference at 2005 in London .