Reuters: Five big emerging economies on Tuesday staked out tough positions on greenhouse gas emissions and food security, ahead of talks on climate change with rich countries in the Group of Eight. In a statement, the five nations urged the G8 countries to shoulder their own responsibilities on climate change by reducing their greenhouse gas emissions by 80-95 percent below 1990 levels by 2050. Mexico, Brazil, China, India and South Africa also urged all developed countries to commit …