Complex sentence: Since 1983 the world top coal producer has been China, in 2011 China produced 3,520 millions of tonnes of coal--49.5% of 7,695 millions tonnes world coal production.
Split into simpler sentences: Since 1983 the world top coal producer has been China. In 2011 China produced 3,520 millions of tonnes of coal--49.5% of 7,695 millions tonnes world coal production.