Agence France-Presse: Kicking off with thousands gathering on the steps of Sydney`s iconic Opera House, global warming protests took place around the world Saturday to mark 50 days before the UN climate summit. From Asia to Europe via the Middle East, activists staged lively events addressing world leaders and to mobilize public opinion around climate issues. Many waved placards bearing the logo 350, referring to 350 parts per million (ppm) of CO2 in the atmosphere which scientists say must not be …