Greenpeace: Presidents Barack Obama and Hu Jintao’s first meeting on 1 April, is a key opportunity for the world’s two largest greenhouse gas emitters to lead the way on tackling climate change. While Obama and Hu are meeting at a critical time in London, the first in a series of United Nations climate negotiations began in Bonn this week, which culminate with the Climate Summit in Copenhagen in December where negotiators will agree the next stage of the Kyoto Protocol. “To save the …