Happy New Year (a few hours early)!!! For my last post of the year, here is some overall analysis of Beijing’s air quality over the past 12 months.
First, the numbers. As usual, I’m working from air quality data downloaded from the Ministry of Environmental Protection’s datacenter. (Direct link to Beijing’s data is here.) There is a bug in the system that prevents the query function from working properly, but you can still scroll through the data and download it manually through copy and paste.
The datacenter reports 363 data points for 2009; 2/18 and 11/14 are mysteriously missing. Assuming those two days were Blue Sky Days yields a Blue Sky Day count of 285 and a calculated average PM10 concentration of 120 ug/m3.
Update 1/14/11: The Beijing EPB’s 2009 annual report states a PM10 concentration of 121 ug/m3.
For anyone who is new to this blog or who needs a refresher, a Blue Sky Day is a day with an Air Pollution Index (API) of 100 or below, which means that the air quality meets China’s National Grade II air quality standard – theoretically “excellent” or “good” air quality. China tallies annual number of Blue Sky Days as a consumer-friendly and easily-understood measure of air quality progress, although the metric is prone to gaming and scientifically meaningless.
PM10 means particulate matter of size 10 microns or smaller, also called “inhalable particles.” In 2009, PM10 was the reported dominant pollutant on 97% of days with an API above 50. (No dominant pollutant is reported on days with an API 50 or below.) I back-calculated PM10 from API using formulas and assumptions described here.
Trends of Blue Sky Days and PM10 concentration since 2000 are shown here:
The Good News: The good news isn’t really that good, but in the interest of balance here are some positive perspectives. First, Beijing’s count of 285 Blue Sky Days in 2009 is well above that of 2008 (274), and also well above the goal of 259. This will keep the trending up in official reporting and for boosting public morale; I imagine this fact will be spun as success / progress in the Chinese media in the days to come. I suppose another bit of good news is that Beijing has achieved what appears to be an improvement over 2008 without the boost of two months of extreme traffic restrictions and factory closures implemented last year during the Olympic period.
The Bad News: My calculated average PM10 concentration in Beijing for 2009 is 120.2 ug/m3, which less than a 1% reduction from 2008’s average. In other words, from the perspective of average particulate matter concentration, there was no improvement in air quality in Beijing from 2008 to 2009. This shows the danger of using “number of Blue Sky Days” as a metric for air quality evaluation – just because the number of Blue Sky Days increases doesn’t mean that air quality has improved.
Interestingly, as a thought experiment, let’s suppose that China’s air quality goal was that all cities should meet the Grade I air quality standard, meaning that a Blue Sky Day would have an API of 50 or below as opposed to an API of 100 or below. If we count these days (shown in the graph above in light blue), we actually see that 2009 was worse than 2008; 2008 had 62 Grade I days, while 2009 had only 47.
Most importantly, regardless of how you spin the data, Beijing’s 2009 level of inhalable particulate matter was still 20% higher than China’s own air quality standard and six times higher than the WHO’s recommended annual PM10 standard. What this means, of course, is that our work continues to be cut out for us moving into 2010 and beyond.
Related post: Summary of Beijing’s 2008 air quality