Environment ministers from the G8 rich nations on Monday urged their leaders to set a global target to halve greenhouse gas emissions by 2050, a small but vital step in the fight against climate change. But they stopped short of suggesting specific interim targets ahead of 2050, a key demand of developing countries in tough UN-led talks to forge a new treaty on global warming by the end of next year. Germany's secretary of state for the environment, Matthias Machnig, said the ministers had sent an important signal to their leaders on the direction in which talks needed to go.