Archive for January, 2011

beijing enjoys first completely blue sky month since 1998

Monday, January 31st, 2011

Beijing’s incredible streak of consecutive Blue Sky Days continues, standing now at 40 days. (Past coverage here and here.) As I noted in my last post, what we are experiencing is not merely some minor or subtle improvement. Beijing’s air pollution levels over the past month have been less than half of what they usually are this time of year. This is remarkable.

The Beijing Environmental Protection Bureau weighed in today in their monthly air quality assessment:




Rough translation (emphasis mine):

In January, Beijing’s air quality met the standard every day. There were 18 Grade I days and 13 Grade II days, an increase of 6 days more than the same period last year. There are 243 days remaining before Beijing achieves its yearly target of 274 (75%) days meeting the ambient air quality standard. This month is the first complete month since 1998 in which every day in Beijing has met the air quality standard.

That every day in January met the air quality standard is a strong testament to the clear results obtained by many years of pollution prevention and control work, especially control of pollution in winter from burning coal.

Experts from the Beijing Environmental Monitoring Center note that car operation and fireworks during the Spring Festival time will affect air quality. Everyone should pay attention to use vehicles reasonably and set off fireworks in a controlled way, so as to reduce the impact of these activities on air quality.

The summary is rather understated given how dramatically improved the air quality was this month. My guess is that the Beijing EPB is as surprised as the rest of us at how terrific the air quality has been recently, and are reluctant to claim too much credit before further analysis is done. While it’s true that we are certainly seeing some fruits of the variety of emission control programs implemented over the past decade, I think that a bigger factor recently has been consistent weather patterns favorable to pollutant dispersion as opposed to major changes in source emissions.

This graph shows my estimations of average PM10 concentration in Beijing in January, 2001-2011. This year is clearly a (very welcome and very dramatic) anomaly:

january pm10

beijing breaks record for longest streak of consecutive blue sky days – best air quality in years

Thursday, January 27th, 2011

Great news! Today is Beijing’s 36th consecutive Blue Sky Day, a day whose Air Pollution Index (API) is 100 or below, indicating “excellent” or “good” air quality. As far as I can tell, this is the longest consecutive streak of Blue Sky Days in Beijing for at least ten years. Previously, there were only three streaks of 30 days or longer, one in 2006 and two during the Olympics.

Although we have seen gaming of the Blue Sky Day metric in the past, in this case both the data and public observation support dramatically cleaner air quality over January 2011 than in months and years past.

On the data side, for the 36-day period December 23, 2010 to January 27, 2011, I calculated an average particulate matter concentration of around 64 ug/m3 in Beijing. (API to PM10 concentration methodology here.) While this is still well above the WHO’s recommended annual limit of 20 ug/m3, this pollution level is less than half of that over the same period in 2009-2010, and is actually on par with the pollution levels during the Olympic (57 ug/m3) and Paralympic (71 ug/m3) periods, which were widely regarded as successful.

Looking at the data another way, an astonishing 18 of the past 36 days have been Grade I “excellent” air quality days in Beijing, which means the API is 50 or below. In 2001, Beijing only had 12 Grade I air quality days the entire year.

From a public observation perspective, I offer up for evidence the conversation I mentioned in my last post which made me start thinking about the streak, this e-mail I received two days ago from another friend:

I’ve been meaning to ask but since pretty much Christmas Eve I feel like has been the best stretch of air quality since I landed here…even better than the Olympics (which I caught the tail end of). My general air quality test is how well I can see the mountains from Tsinghua or Andingmen bridge. Rarely has there been a miss. I must have clearly seen stars all but a handful of nights and I can’t think of a day that’s looked polluted from start to finish. Are my eyes merely deceiving? Is the wind just being very helpful? Or has there actually been a drop locally?

and finally, the Beijing Air feature from the Asia Society, which features daily pictures, monthly averages, and weekly comparisons of Beijing’s air quality with that of New York. Here’s the past week comparison between Beijing (top row) and New York (bottom row):

asia society jan 11 1
They note, “This week has been by far the cleanest in terms of both blue-ness and air quality stable performance. Even New York looked less impressive.”

So why has the air quality been so uncharacteristically good recently? Unfortunately, I have no data-backed theories, although I would guess it’s a combination of existing pollution control programs and standards beginning to bear fruit, economic slowdown prior to the Chinese New Year holiday, and really favorable weather patterns that have prevented any pollution from building up. (Perhaps the lack of pollution build-up is also related to similar weather patterns that have prevented any measurable precipitation in Beijing since October 23rd.)  Regardless, it’s a great air quality start to 2011. Let’s see how much longer the streak can go.

how long can beijing’s good air quality streak last?

Sunday, January 16th, 2011

Over the past few weeks in Beijing, the air quality has seemed uncharacteristically good. In fact, Beijing has had 25 consecutive Blue Sky Days – days for which the Air Pollution Index has been at 100 or below, representing “good” or “excellent” air quality. This morning a friend remarked that she couldn’t remember any other time when the air quality has been this good for so long continuously. I decided to investigate her claim.

Here’s what I found. Going back to 2001, I only found 6 streaks of 25 or more consecutive Blue Sky Days. They were as follows:

6/24/06 – 7/28/06 (35 days)
7/31/06 – 8/24/06 (25 days)
1/21/08 – 2/18/08 (29 days)
7/28/08 – 8/28/08 (32 days)
8/30/08 – 9/29/08 (31 days)
8/19/10 – 9/14/10 (27 days)

The two streaks in the summer of 2008 were clearly linked to the temporary pollution reduction policies put in place for the Olympics and Paralympics. I’m not sure what caused the other streaks, especially the excellent summer of 2006.

The current streak began on 12/23/10. Let’s see how long it can go! Track it yourself here at the MEP datacenter.

summary of beijing’s 2010 air quality

Friday, January 14th, 2011

Happy New Year! For each of the past two years around this time (link to 2008, link to 2009), I’ve posted a summary of the previous year’s air quality in Beijing. This post contains some data and notes on 2010.

My data source, as always, is the datacenter of the Ministry of Environmental Protection, which archives historical Beijing air quality data here. (Note that I’m using the daily averages, not the recently released hourly data.) All I’m doing is copying the data into Excel, then parsing it and doing some conversions to look for patterns. The most important conversion is converting Air Pollution Index (API) to ambient particulate matter (PM) concentration, using the equations described here. This is important for two reasons. First, the conversion allows for averaging, which should not be done with API data directly. Second, ambient PM concentration is a much better indicator of the health impact of air pollution in Beijing, allowing for direct comparison to international air quality standards and existing health effect studies.

Now on to the data. The datacenter reports 363 data points for 2010 (3/15 and 5/21 are missing). Assuming those two days were Blue Sky Days yields a Blue Sky Day count of 286 and a calculated average PM10 concentration of 122 ug/m3. The Blue Sky Day count of 286 has been confirmed by the Beijing EPB, but the PM10 concentration value probably won’t be released for another few months.

As a reminder, Blue Sky Days are days for which the API is at or below 100, which China deems “excellent” or “good” air quality. Cities count the annual number of Blue Sky Days as an easily-understood measure of air quality progress, although the metric has been gamed in the past and is actually scientifically meaningless.

This figure shows trends of Beijing’s Blue Sky Days and PM10 concentration since 2000:

beijing air quality trends 00-10
The Bad News: Beijing’s air pollution levels, as represented by ambient particulate matter concentration, have remained flat for the past three years, actually getting slightly worse from 2009 to 2010. This is consistent with results reported in mid-2010. Beijing’s air quality still does not meet China’s own air quality standard, and is six times worse than the recommended particulate matter target set by the WHO.

The Good News: Beijing’s 286 Blue Sky Days in 2010 far exceeded its target (266), and miraculously managed to beat last year’s total by just one day. In addition, there was a slight increase in the number of Grade I (“excellent”) air quality days as compared with 2009 (as shown in the above graph in light blue). This is dramatic turn-around from the way things looked in the first half of the year. Given that over 700,000 vehicles were sold in Beijing in 2010, I suppose the fact that the pollution didn’t get even worse can be viewed in some respects as a success.

Beijing’s Environmental Protection Bureau really struggled to call 2010 a success. On December 31st, they released a short note stating, “今年我市空气质量二级和好于二级的天数累计达到286天,占78.4%,比去年多1天,实现了空气质量连续12年持续改善,” meaning, “This year, the number of days in our city meeting the Grade II or better air quality standard totaled 286, representing 78.4% of all days, one more than last year. This has realized 12 consecutive years of air quality improvement.” The last statement is highly dubious, especially given my preliminary conclusion that the average PM10 concentration was higher in 2010 than 2009. It will be interesting to see how and if the EPB’s statements change when the PM numbers are released in the environmental annual report later this year.

Related posts:
Summary of Beijing’s 2009 air quality
Summary of Beijing’s 2008 air quality