Miami Herald: South Florida’s three largest counties have competed — for jobs, conventions, sports teams, cruise ships, federal funds and many other things — as much as they have cooperated over the years. But Friday, Miami-Dade, Broward and Palm Beach, joined by Monroe, agreed that they share a large, looming problem they better start working on together fast: global warming, which brings with it the scary prospect of waves washing against abandoned beachside hotels before the century is …