Agence France-Presse: Final preparations were underway here Sunday for a marathon UN conference on climate change, amid beefed-up security, activists’ clamour and warnings that a hothouse planet loomed if the talks failed. UN Secretary General Ban Ki-moon issued an upbeat note on the eve of the landmark conference, predicting mankind would strike a blow against the 21st century’s great peril. The climax on December 18 — to be attended by more than 100 heads of state and government — should deliver …