China accused some of the richest nations in the world of “backsliding” on pledges to clean up pollution and provide $100 billion a year in climate-related aid by 2020. The comments at a United Nations conference on global warming in Poland spearheaded a push by a group of the 49 Least Developed Countries for clarity on when those promises will be fulfilled. Industrial nations remain about $30 billion short of their pledge to ramp-up climate-related aid to $100 billion a year by 2020. Developing nations are resisting measures that would ensure transparency in the way greenhouse gas emissions cuts are...