My theory is that it rises when Beijing has record pollution, and slides as the air quality improves.
I speculate the Chinese reduce/boycott Australian Iron ore and coal, and start burning using local ores - until they just cant breath, then go for the good stuff.
Edit: Boycott is the wrong word. I meant ease up, reverse positions on futures contracts, and use stockpiles and press releases to force stop losses in the wanted direction; and or switch to SA sources to amplify this sudden 'downturn'. Maybe cunningly manipulate is the right word.If they use their central demand numbers smarter - they get more cheaper. Plus they have some flexibility on outputs by shutdowns. The calculus is the area under the spot curve. They seem to win - except when pollution hits badly. Same trick as speed share trades, only bigger.
As the 2nd largest Oil Importer, I suspect they have a large hand in oil too - traders have wised up,hence needed to do a deal with gazprom to remove easy 'cyclical' bets from futures. I go on a limb and say should the oil price spike, and with certain aussie coal mines shut down, aussie and coal may have an upside, if the weather blows the pollution away.