The number of coal mines in the US has hit a record low, keeping in mind that records only go back to 1923. (At some point the number was zero.) While size may vary, the total coal output is also diminishing, and the number of new mines is also decreasing. Increased use of natural gas and renewable energy means less demand for coal, which also means fewer emissions for the country. The other key effect is the flattening of electrical demand, whether through a mix of the recession, new efficiencies, and new personal practices. All are signs of improvements in mitigating climate change.
(Click on the chart for the link.)