[Note : I am getting more concerned that the source data just does not accurately represent the air experience.� This was commented on widely on 18 June 2009 when the air looked real bad but was reported as 158 “slightly polluted”.� Other independent measurements put this day in the “hazardous” category.� I wonder if there is any point continuing.

One of my (acceptable) personal hobbies is monitoring Beijing’s air pollution statistics. My graph based on Beijing’s published statistics is shown below. You can make your own mind up about whether the numbers are improving.� While I had my doubts about improvements, it seems to me that the Beijing Olympics were possibly the biggest factor in improvements since mid-2007.� Of course, the shutting down of a few heavy industries and moving them to other parts of the country may be only exporting the problem elsewhere.� Now its just a battle to keep improving emissions against the seemingly unstoppable number of cars appearing on Chinese roads.

The index is a unique index used by the Chinese authorities and apart from making it difficult to compare with indices used in other countries, the maximum recorded index value is 500, meaning anything more than 500 is recorded as 500.� Note that there was in early 2008 some discussion over the possible “adjustment” of numbers in order to meet targets. It has been suggested that replacing monitoring stations near the centre of Beijing with ones out past the 4th ring road has distorted the results in a downward direction. There is also pretty convincing statistical evidence that some figures just below 100 were astutely adjusted downwards to get below this key target level. Read the following link and decide for yourself :

http://iopscience.iop.org/1748-9326/3/3/034009/fulltext?ejredirect=migration

Beijing Average Monthly Air Pollution Index

Month	2000	2001	2002	2003	2004	2005	2006	2007	2008	2009	2010	2011	2012
Jan		113	116	93	89	90	128	102	83	83	74	51	86
Feb		119	110	101	108	76	98	110	73	89	77	101	73
Mar		158	155	105	125	91	132	96	109	92	108	83	82
Apr		131	168	104	116	137	177	94	103	83	83	108	115
May		154	94	94	87	93	120	106	142	83	89	80	96
Jun	118	106	89	95	97	92	86	117	91	78	85	86	73
Jul	86	84	86	94	77	86	71	94	77	74	87	73	61
Aug	89	80	96	86	86	88	74	82	56	76	70	77	70
Sep	95	92	91	86	94	98	95	89	57	85	70	73	61
Oct	86	118	98	98	139	102	107	80	75	82	82	91
Nov	128	102	105	119	89	149	115	103	80	97	103	91
Dec	110	102	135	94	126	82	120	138	98	103	95	73

The green line plots the daily values while the red line is a smoothed trendline. The Firefox extension called “Image Zoom” is not bad for manipulating the zoom or you can just click on the image to see it in its own window.