Associated Press: China, the world’s biggest emitter of greenhouse gases, faces serious challenges to its efforts to cut environmental pollution, with one key pollutant increasing for the first time in three years, a senior Chinese official said Thursday. Sulfur dioxide emissions increased by 1.2 percent year-on-year in the first quarter of 2010, the first increase since 2007, Zhang Lijun, vice minister for environmental protection, told a news conference. "This sounded the alarm for our …