BBC: Heads of the G8 leading industrial countries are set to meet emerging nation leaders to try to push through a new deal on limiting global warming. US President Barack Obama will chair the key session at the G8 summit in the Italian city of L’Aquila. On Wednesday, the G8 said it had agreed new targets for limiting global warming and carbon emissions. But correspondents say emerging nations appear reluctant to sign up and tough negotiations lie ahead. The second …