A China Daily report today mentions Beijing’s 2010 Blue Sky Day target as 266. This is the first time I’ve seen the target referenced; I’m not sure how/when they set or publicize them. Perhaps they are in Beijing’s Five Year Plan. Does anyone know?

This China Daily report also mentions Beijing’s 2009 Blue Sky Day total, 285, representing the first time I’ve seen it mentioned in English-language domestic media (although Xinhua covered the accomplishment in Chinese on 1/1.)

Recent targets and totals are shown below. Note that the 2010 target is below the number of Blue Sky Days achieved in both 2008 and 2009.

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.

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Update 1/14/11: The Beijing EPB’s 2009 annual report states a PM10 concentration of 121 ug/m3.
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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

Although a little late, I do want to highlight a rather unexpected comment from the Beijing EPB at a press conference in early July. As reported in the Time blog:

[The Beijing EPB] spent much of their press conference Friday responding to doubts about the veracity of their numbers. Last year an American environmental consultant pointed out that the official numbers showed a disproportionately high number of days that fell just within the official target for a “blue sky day.” Yu Jianhua, head of Beijing’s environmental monitoring center, said the local government used emergency measures such as closing down construction sites on days when it expected pollution would exceed targets. That led to the high number of days just under the cutoff, Yu said.

This is the first time I’ve seen the Beijing EPB both directly acknowledge that a statistical anomaly in the number of blue sky days exists and provide a concrete reason why. The statistical anomaly I’m referring to can be be seen in this figure, from a 2008 report by environmental consultant Steven Andrews. The graph appears to show data biasing right around the “blue sky day” cut-off point (in this case, a PM10 concentration of 150 ug/m3).

It has been interesting to watch the evolving responses from the EPB to Mr. Andrews’ discovery – from official data – of what appears to be blatant data massaging to achieve an artificial result. In February 2008, Beijing EPB spokesperson Du Shaozhong infamously responded to criticisms of data manipulation with, “this phenomenon does not exist. ” By July 2008, in a press conference before the Olympics, the Beijing EPB response had shifted to the bewildering  “some convenience maybe taken in very adverse situations to improve the air quality within 9 square kilometers so that the API can remain at or below 100.” (The WSJ reported on this response the following day.)

Now, however, we have a definitive claim from the Beijing EPB that the preponderance of API values just below the blue sky day cut-off point resulted from emergency measures taken on days which were predicted to be dangerously close to the limit.

As is so often the case in China, this reponse only makes me ask more questions. Questions like:

- Why didn’t the Beijing EPB admit this last year, as soon as Mr. Andrews’ report came out?
- How are such accurate predictions made? Can we have more details on the program, like which factories or construction sites were closed?
- Why do this at all? Is there really a critical human health benefit to a 99 API day as opposed to a 101 day? (Answer: not really, since where we need to be is below 20.)
- Why were these emergency shut-downs conducted from 2003-2007, but not in 2008?
- Was this program really conducted in dozens of cities around China?

I can keep asking questions of course, but I think it’s time now to invoke Occam’s Razor in support of the more obvious conclusion…

More info in related posts on this blog:
October 2008: problems with the blue sky day metric
March 2009:  looking for biasing in 2008 blue sky day data
June 2009: new report shows widespread air quality data manipulation

Final note: I am playing catch up on posting after falling behind the last few weeks with the site redesign and work distractions. Apologies in advance that some of the commentary will be on “old” (e.g., from July) news.

When I wrote yesterday about the China Daily article on the discrepancies between China’s officially reported air quality data and the US Embassy’s BeijingAir Twitter feed, I didn’t realize that the China Daily story appeared on the site’s home page along with an incredibly direct web survey:

Web surveys are, of course, not scientific or reliable at all, but nonetheless here’s a screen capture of the results as of around 11am this morning:

It’s difficult to imagine such a critical survey happening on a Chinese-language state media site, but I will keep an eye out for anything comparable.

Lastly, for the record, there are several mistakes in the China Daily story that I should point out. Three are in this sentence alone: “A blue-sky day is when the city’s air pollution index, the level of five airborne pollutants, falls below 100, indicating that no health implications exist.”

First, MEP makes no claim that blue-sky days have “no health implications,” only that those days have the poorly-defined “excellent” or “good” air quality. Air quality on blue-sky days can certainly have negative health implications, especially for sensitive populations in the short term and for everyone in the long term. What MEP calls “good,” the US EPA calls “moderate,” saying, “Air quality is acceptable; however, for some pollutants there may be a moderate health concern for a very small number of people who are unusually sensitive to air pollution.”

Second, the air pollution index only covers three pollutants, not five. I’m not sure how China Daily made this mistake, because later in the article they describe the number correctly (”the current evaluation system uses only three indices: Sulfur dioxide, carbon dioxide and PM 10s”), although they get the pollutants wrong. (The three are sulfur dioxide, nitrogen dioxide, and PM10.)

Third, this is minor, but a blue-sky day is a day in which the API is technically 100 or below, not below 100.

This past spring, the months of April and May in Beijing were reported as the cleanest April / May in a decade. (Sources for April: China Daily and Beijing EPB, see also my previous post; sources for May: Xinhua and Beijing EPB.)

Independent of the quantitative results, these reports seem to confirm what a lot of people have been mentioning to me, that this past spring has seemed surprisingly clean.

Let’s evaluate the truth in all of this. The following graph shows average API*, average PM10 concentration, and number of Blue Sky Days for the period April-May from 2005 through 2009:

From these numbers, the results are pretty clear: the period April-May 2009 in Beijing was indeed significantly better in terms of air quality than the same period in any of the previous four years. (I could have looked farther back, but I decided only to look at five years total for this analysis.)

Here are some comparisons of 2009 vs 2005-2008 averages:

I think it’s probably fair to say that the air quality this April and May was 30-40% better than the average air quality during the same period over the previous four years.

As usual, we should celebrate the progress while being mindful of the significant improvements still required. My calculated average PM10 concentration for this period, 117 ug/m^3, is still well above China’s annual target (100 ug/m^3) and well well above the WHO’s ideal target for developed nations (20 ug/m^3). It is also well above my estimate for the average PM10 concentration during last year’s two-month Olympic period (79 ug/m^3).

Related:
Summary of Beijing’s 2009 first quarter air quality
Summary of Beijing’s 2008 air quality
Update on fall air quality in Beijing

*I don’t really like averaging API, because it can lead to some misleading results (further discussion in this post), but despite that I still think it has value as an indicator here.