The central business district in Beijing on Monday, when the capital was engulfed in a sandstorm.Gilles Sabrié for The New York Times The Communist Party has made great strides in reducing China’s pollution, but a perfect storm of northern winds and an industrial rebound has created dangerously high levels of pollution countrywide. When China’s leader, Xi Jinping, met with Communist Party delegates from Inner Mongolia last week, he urged them not to relent in the fight to improve the environment. “We must adhere to the concept that clear waters and green mountains are as good as mountains of gold and silver,” he said. On Monday, large parts of China experienced just how bad the environment can still be. The largest and strongest dust storm in a decade swept across northern China, grounding hundreds of flights, closing schools in some cities and casting a ghastly shroud over tens of millions […]