br Cranes unload coal from a cargo ship at a port in Lianyungang, Jiangsu province, China December 8, 2018. REUTERSStringer BEIJING (Reuters) - China’s December coal output climbed 2.1 percent from the year before, government data showed, hitting the highest level in at least three years as major producers ramped up production amid robust winter demand and after the country started up new mines.