China's jump in coal use of about 2000 Mt/yr in just a decade represents about 6 gigatons of CO2 emissions a year -- one-fifth of current world emissions.
(No, I'm not blaming them -- China's per capita CO2 emissions are still less than 1/3rd that of the US. India -- who seems headed up the same arc as China but about 30 years behind -- emits less than 1/10th that of the US. If China and India were to emit at the same per capita rate as the US, and the rest of the world stayed constant, worldwide emissions would more than double to 63 Gt CO2/yr. If the entire world emitted like the US, emissions would be 114 Gt CO2/yr, almost 4 times the current level.)
By the way, total US coal production is only about 1,000 Mt/yr, and it peaked in 2008. So you can see why they want to send it on trains from Wyoming to eastern Oregon, ship it by barges down the Columbia River, then ship it across the Pacific Ocean to China. There's a big fight starting here in Oregon about this.