A couple good links regarding power usage:
Mining power usage
Power usage comparisons
On that comparisons page they looks at the power used in the US alone to power always-on but idle devices: result is that power used for idle devices would power the entire BTC network for 1.9 years.

Regarding China also taking several large aluminum refining plants offline, that is a double 'win' if their goal is to reduce carbon emissions. The reason is because not only does it require vast amounts of energy but also because the process of reducing Al2O3 into Al combines the liberated O2 with carbon from the electrodes used and that produces CO2. How much? 11.5 tons of CO2 per ton of Aluminum. That number is including the CO2 from using coal to produce power. When Hydro is used that same article states that emission drops to two to four tons of CO2 per-ton of Aluminum.