Archive for January, 2013

timeline of china’s official resonses to recent severe pollution

Thursday, January 24th, 2013

List last updated Beijing time 4/1/13 6:00am

In the fall of 2011, public discontent over a series of poor air quality episodes in Beijing ultimately led to an impressive series of actions by China’s national Ministry of Environmental Protection (MEP) and the Beijing Environmental Protection Bureau (EPB). It took a few months, but by February 2012, China had issued a revision to the ambient air quality standards, a new definition of the Air Quality Index, and by the end of the year, had completed and began operating a network of real-time PM2.5 monitors in 74 cities through the country.

So if the “wins” of the fall of 2011 were great strides towards monitoring and reporting, then here’s to hoping that this most recent episode of crazy bad air will turn into progress on actually reducing emissions themselves.

To help track the progress, I’m creating here a timeline of “official” Chinese government responses to date on the recent severe pollution in Beijing and many other cities across China. This includes major announcements I have seen from MEP and the Beijing EPB; if anyone knows of other key announcements I’ve missed, from other ministries, or from other cities like Shanghai, let me know and I’d be happy to add them. I will be curious to see where this list goes in the coming months.

Note 1: Major announcements shown in bold.
Note 2: MEP often back-dates announcements; the dates shown here are the “official” release dates, even though often the announcements don’t go up publicly until a week (or more) later.

1/12: “Crazy bad” air hits Beijing and other cities across China, sparking unprecedented reaction from domestic and international media and the general public
1/14: MEP issues its first official response, “Notice requiring each area to conscientiously conduct air quality monitoring and early warnings on heavy pollution days”  环境保护部发出通知要求各地认真做好重污染天气条件下空气质量监测预警工作
1/14: MEP issues a draft arsenic pollution prevention technical standard for public comment 关于征求《砷污染防治技术政策》(征求意见稿)意见的函
1/15: MEP and Beijing EPB issue a brief evaluation and explanation of the pollution, “Beiing EPB analysis of the extended severe pollution – large emissions the fundamental reason” 北京市环保局分析持续严重污染原因 排放量大是根本原因
1/15: Vice Premier Li Keqiang issues a brief and fairly anodyne comment pledging action: 李克强谈空气污染治理问题:我们必须有所作为
1/17: MEP issues the second round draft light-duty vehicle China 5 tailpipe emission standard for public comment 关于征求《轻型汽车污染物排放限值及测量方法(中国第五阶段)》(二次征求意见稿)意见的函
1/17: MEP issues a draft mercury pollution prevention technical standard for public comment 关于征求《汞污染防治技术政策》(征求意见稿)意见的函
1/18: Beijing EPB issues a super strange announcement warning websites not to claim official approval to report air quality numbers: 关于对部分社会化监测机构冒用我局名义进行虚假宣传有关说明的公告
1/19: Beijing issues a major new set of comprehensive regulations on air pollution prevention and control: 《北京市大气污染防治条例(草案送审稿)
1/23: Beijing’s mayor Wang Anshun makes a speech in the context of the Beijing People’s Congress with some numbers to back up the new regs (not sure the best link for this; perhaps this work report 《政府工作报告》解读:展望·2013年的北京)
1/23: Beijing issues new tailpipe emissions equivalent to Euro 5/V for gasoline cars and municipal diesel vehicles, implementation starts almost immediately on 2/1: 北京2月1日起执行第五阶段机动车排放标准
1/24: MEP Minister Zhou Shengxian holds National Environmental Protection Work meeting, pledges some actions 全国环境保护工作会议在京召开
1/24: Influential Tsinghua professor says China’s Clean Air Act revisions moving forward (I will update official link when I find one)  机动车污染防治条款浮出水面 环保不达标召回
1/25: MEP releases a notice about the implementation of Stage II emission limits for gasoline non-road mobile machinery: 关于实施国家第二阶段非道路移动机械用小型点燃式非手持式发动机排放标准的公告 (note: I can’t figure out how this announcement changes anything about existing schedule)
2/4: State Council issues roadmap for diesel and gasoline fuel quality improvement: 温家宝主持召开国务院常务会议 – 决定加快油品质量升级
2/6: MEP issues draft for public comment of “Atmospheric Fine Particle Pollution Prevention and Control Technology Policy (trial)” 环境空气细颗粒物污染防治技术政策(试行)
2/7: SAC issues new diesel fuel quality standard (China IV): GB19147-2013
2/16: MEP issues statement about air quality during the Chinese New Year holiday: 环境保护部通报春节期间我国部分城市空气质量状况
2/16: MEP approves Tsinghua University to build an air pollution control laboratory 关于同意建设国家环境保护大气复合污染来源与控制重点实验室的复函
2/17: MEP issues 12th Five-Year Plan for Environmental Standards: 关于印发《国家环境保护标准“十二五”发展规划》的通知
2/26: MEP releases two new draft standards on air quality monitoring, including monitor placement, for public comment: 关于征求《环境空气质量评价技术规范(试行)》等两项国家环境保护标准意见的函
3/15: Beijing releases the 2013 Clean Air Action Plan 我市发布实施2013年清洁空气行动计划
3/22: MEP releases a notice about “Implementation plan for stage II monitoring for ambient air quality standards” 关于印发《空气质量新标准第二阶段监测实施方案》的通知
3/29: Beijing and Tianjin sign an agreement to work together on improving air quality 京津两市签署协议加强环保合作共同致力于改善环境质量
3/29: News reports suggest that Beijing will spend 100 billion RMB to combat air pollution as part of its previously released 2013清洁空气行动计划

I will try to update this from time to time. Note that not all of these are direct responses to the pollution episodes; for example, the draft standards have been under development for months if not years. I don’t know whether or not the decision to release them for public comment now is linked to the recent pollution episode…

seeking solutions to china’s air pollution crisis

Friday, January 18th, 2013

A version of this essay, in Chinese, first appeared on the New York Times’ Chinese website.

Over the past week, hundreds of cities across China experienced dangerous spikes in air pollution levels. With air quality degrading to 20 or even 30 times worse than what is deemed safe by the World Health Organization (WHO), even our language strained to describe it (what can be worse than “hazardous”?). As visibility dropped to nearly zero and hospital admissions surged, the Chinese public began demanding both explanations and actions to prevent similar episodes in the future.

Unfortunately, extreme pollution events are common in China – especially in Beijing. This week’s pollution was notable for being the worst in recent memory, but the pollution accumulation spike was not unique – and next time it may even be worse. Even more important from a long-term health perspective, annual average air pollution levels in many cities in China remain unacceptably high. Until the government succeeds in implementing comprehensive policies requiring deep and permanent emissions reductions throughout the country, China will continue to struggle with air pollution for the foreseeable future. Fortunately, the policy and technology solutions to solving China’s air pollution crisis are well-known. Even better: these solutions will save millions of lives and can be implemented without sacrificing economic growth.

Causes of air pollution
China’s rapidly increasing numbers of coal-burning power plants, inefficient industrial facilities, and motor vehicles burning dirty fuel produce an enormous volume of air pollution every day. Pollutants directly emitted by these sources react with each other in the chemical soup that is the atmosphere, producing new types of “secondary” pollution including health-damaging ground-level ozone. This pollution is then transported through the atmosphere by prevailing meteorological conditions. When winds are stagnating – as was the case last weekend throughout much of eastern China – air pollution can accumulate rapidly. Geography can further complicate the pollution story. Cities bounded on two or more sides by mountains – such as Beijing and Los Angeles – are even more susceptible to severe pollution episodes. In Beijing’s case, winds blowing gently from the south carry air pollution from across central and northern China and trap it against the mountains to the north and west of the city.

Air pollution is regional
Because pollutants travel easily in the atmosphere (and some pollution sources, like vehicles, travel themselves), air pollution is fundamentally a regional problem, requiring regional or – even better – national solutions. Scientists have estimated that between one-third to two-thirds of Beijing’s pollution is caused by emissions in the surrounding provinces. Beijing’s government has implemented dramatic and impressive measures over the past decade to reduce pollution emissions within its boundaries; for example, the city has nearly eliminated coal-burning, implemented the most stringent vehicle emissions and fuel quality standards in the country, scrapped hundreds of thousands of high-emitting cars and trucks, and forced major industrial plants to relocate. However, pollution level spikes in the city continue to occur throughout the year, and average air pollution levels are far from meeting even China’s air quality standards. Though cities undoubtedly have a critical role to play in reducing emissions in China, air pollution cannot be solved exclusively at the municipal level.

Neither monitoring and reporting nor temporary policies are enough
The Chinese government has reacted to the recent, severe pollution episode by pledging to improve pollution data accuracy and transparency, and by implementing short-term, “emergency” pollution reduction policies like restricting government car use and temporarily halting factory production. Similar (though even more draconian) temporary policies were proven to be an effective regional air quality improvement strategy during the 2008 Beijing Olympic Games. However, although these temporary policies may have some impact on reducing the severity of short-term pollution level spikes, they will do little to address the elevated day-to-day average pollution levels that are killing hundreds of thousands of people in China every year.

As for data transparency improvements, these are important and welcome steps, particularly the recent launching of real-time air pollution reporting for 74 cities in China and pledges to improve early, public warning systems during hazardous pollution conditions. However, monitoring and reporting are fundamentally only descriptions of the problem, not solutions themselves.

Solutions: deep and permanent cuts
The fundamental solution to China’s air pollution crisis is the rapid introduction of deep, permanent emissions reduction policies for all sources, especially power plants, industrial factories, and motor vehicles. For such policies to succeed, many of the necessary steps – for example, confronting entrenched state-owned enterprises and significantly expanding and empowering China’s national environmental protection authority – will not be easy. But only through long-term reductions in the total volume of air pollution produced in the country will pollution level spikes be eliminated, and average air quality begin to improve in all Chinese cities.

Consider the case of motor vehicle emission control. With China now the global leader in automobile production and sales, emissions from cars, buses, and trucks are a large and growing – and sometimes overlooked – source of air pollution. Of particular concern are long-distance diesel trucks belching black smoke as they travel regionally between factories, distribution centers, and cities. China’s Ministry of Environmental Protection has already issued a policy, “China IV,” that aims to reduce dangerous particulate matter emissions from new trucks by 80 percent. However, MEP has been forced to delay nationwide implementation of these standards twice already – for a total of two and a half years – because the quality of diesel fuel produced by China’s state-owned refineries significantly lags behind what is required for the new truck technologies to function properly. Furthermore, immediate improvements in China’s nationwide fuel quality will not just enable the introduction of “China IV” trucks. They will also facilitate the introduction of future “China VI” vehicles requiring tailpipe filters which eliminate nearly all particle emissions.

Even once this and other standards do go into effect, the Chinese government faces severe capacity shortages to properly enforce them. In the United States, the Environmental Protection Agency employs some 18,000 government officials. How many are there in China’s Ministry of Environmental Protection? Just a few hundred.

Economic growth can continue
In the 1970s, the United States faced an air pollution crisis not so different from that of China today. Cities like Los Angeles regularly experienced both short-term spikes and dangerously elevated average levels of air pollution. But stringent, wide-reaching, permanent control programs implemented for a variety of sources in the United States have produced dramatic results. From 1980 to 2010, emissions of major air pollutants in the United States were cut by over half – even as GDP more than doubled. And because the societal costs of air pollution – hospital bills, reduced productivity and missed work days due to illness, premature death, agricultural loss, and more – can be exceptionally high, analyses in the US have regularly shown that pollution reduction policies deliver total societal benefits far outweighing their costs – often by a factor of five to ten or even higher.

China is no different. The enormous, current economic costs from the health burdens of air pollution in China have been estimated to total at least 1.2 percent of GDP. And this doesn’t even factor in additional “hidden” losses from, for example, damage to China’s international image. China’s past three decades of remarkable development have produced enormous gains for average citizens. But they have also produced dramatic increases in emissions of air pollutants. Fortunately, experience throughout the developed world proves that economic growth can thrive even while air pollution is reduced. This week, China’s Vice Premier Li Keqiang responded to China’s severe pollution with pledges of increased government action. Only if this action includes critical steps such as deep, permanent cuts in emissions from all sources, strong enabling policies like improvements in fuel quality, and broad expansion of China’s environmental authorities, will China’s days of “crazy bad” air finally be gone forever.

turning the conversation about Beijing’s air pollution toward solutions

Tuesday, January 15th, 2013

This post originally appeared on the ICCT Staff Blog.

Over the past weekend, poor meteorological conditions contributed to a severe accumulation of air pollution in Beijing and hundreds of other cities in northern and eastern China. The extreme pollution was the worst in recent memory, yielding hundreds of media reports both within China and around the world. In addition, tens of millions took to Twitter and China’s Twitter-like service, Weibo, to post their thoughts and complaints. Unfortunately, such extreme pollution accumulation episodes are common in Beijing. And even when meteorological conditions are good, average pollution levels in Beijing are still unacceptably high. Until China takes critical steps towards reducing emissions, poor average air quality and occasional “crazy bad” episodes will continue.

Vehicles are a critical source to control
Vehicles are typically by far the largest source of human exposure to air pollution in densely packed urban areas. Plus, the contribution of vehicle emissions to air pollution in China is increasing as the population of motor vehicles in Beijing and around China continues to grow rapidly. Implementing stringent controls to mitigate the pollution impacts of China’s motor vehicles must be a key priority in parallel with controlling other sources such as factories and power plants.

Moreover, such action needs to take place at the national level. Because vehicles (especially trucks and long-distance buses) travel in and out of cities, only stringent national-level regulations can ensure that all vehicles are controlled effectively no matter where they travel. In recent years, Beijing has made a series of impressive steps towards controlling pollution within its own boundaries (e.g. the most stringent vehicle standards in the country, the cleanest fuel quality standards in the country, scrapping >500,000 old polluting vehicles over the past two years, and more). However, the city still struggles to improve air quality because perhaps 34%-70% of Beijing’s pollution is regional, coming from dirty vehicles and industrial sources polluting in the surrounding provinces.

Short-term actions to control motor vehicle emissions in China
Two simple steps could make a huge and near-term difference in improving air quality in Beijing and throughout China, while simultaneously demonstrating the new Chinese government’s commitment to reducing pollution emissions:

1) Immediately issue new fuel quality standards with supporting fiscal policies to reduce nationwide diesel sulfur levels to below 10 parts-per-million (ppm). Because high sulfur levels in fuel can poison advanced emission control technologies, improving fuel quality, especially reducing sulfur levels, is a critical prerequisite to introducing more stringent vehicle tailpipe emission standards. In 2011, China’s State Council announced that preferential fiscal policies would be utilized to encourage the supply of higher quality fuels nationwide. However, these fiscal policies have not yet been issued; a new fuel quality standard is stalled in the review phase; and nationwide diesel fuel sulfur levels continue to stagnate at unacceptable levels of 350ppm or higher. Resolving the fuel quality issue is a critical step to facilitate continued progress in vehicle emission control in China.

2) Ensure that the China IV truck and bus emission standards are implemented this year without further delays. China’s next stage nationwide tailpipe emission standard for trucks and buses, called “China IV” (equivalent to “Euro IV”), aims to cut emissions of PM and NOx from diesel vehicles by 80% and 30%, respectively. However, because these vehicles need to be fueled with higher quality fuel which is not yet supplied nationwide, MEP has twice delayed the introduction of these standards across China. The current implementation date is July 1, 2013. In parallel with resolving the fuel quality issue, China should commit to introducing these standards without any additional delays.

Medium and long-term action to control emissions from motor vehicles
The aforementioned short-term, immediate actions will not be enough to solve China’s long-term motor vehicle emissions problems. Last month, China laid out a number of impressive medium-to-long-term regional air quality improvement actions in its “12th Five-Year Plan for Air Pollution Prevention and Control in Key Regions.” While the plans outlined in the document represent significant progress, the plan does not call for the most important step China can make towards long-term control of vehicle emissions: establishing a clear nationwide timeline for the introduction of global best-practice “China VI/Euro VI” vehicle tailpipe emission standards. Only with the introduction of these standards will diesel trucks and buses – some of the most polluting vehicles on the road – be required to install particulate filters to reduce >99% of PM2.5 particle emissions. Filters belong on cars, not people.

Monitoring and reporting: a recent success story, but only the first steps
In the fall of 2011, public outcry over a series of heavy pollution episodes in Beijing was fanned by social media into enormous public pressure on Chinese authorities to respond. They did. In February 2012, China’s Ministry of Environmental Protection (MEP) issued two major new regulations: a revision to the ambient air quality standards to include PM2.5, and a new definition of China’s Air Quality Index. By the end of the year, China had completed and began operating a network of real-time PM2.5 monitors in 74 cities through the country. The Chinese government deserves praise for these important steps towards air pollution data transparency.

However, air quality monitoring and reporting are only first steps. Now the challenge is how to achieve rapid and significant emissions reductions in order to improve urban air quality. The above three steps – rapid improvement of fuel quality, introduction of China IV standards for trucks and buses this year, and establishment of a clear timeline for early introduction of China VI – will make huge differences in reducing toxic air pollution in Beijing and throughout China. In fall 2011, the public debate led directly to new standards on air quality monitoring and reporting. It’s time now to turn the current pressure towards the more fundamental issues of how and when to cut emissions themselves.

proof of linear extrapolation of embassy pm2.5-aqi relationship above 500

Monday, January 14th, 2013

Well, I’ve officially been called “geeky” on Twitter. I wear the label with pride. Not wanting to let my fans down, I decided to prove my earlier conjecture that the US Embassy linearly extrapolates the AQI-PM2.5 relationship from the EPA’s 400-500 range for concentration values above 500. As I noted before, this is NOT supported by regulatory language in the US, since the PM2.5 concentration almost never goes above 500.

Here’s a plot of the US EPA’s regulatory AQI-PM2.5 relationship definition (blue, stops at 500) as well as a smattering of data from the Embassy monitor (red). Looks pretty clear that the Embassy is just using the EPA’s same AQI-PM2.5 relationship from 400-500 for all values above that.

demystifying air quality numbers

Sunday, January 13th, 2013

There are lots of numbers used to describe air quality these days in China. This post is intended as a glossary to demystify the different numbers currently used by various sources.

Concentration: The most direct way to report air pollution would be the concentration of a given pollutant in the air. This is straight-forward science and measurement. Example: PM2.5 concentration is 950 micrograms per cubic meter (ug/m^3).

Although concentration is straightforward scientifically, there are a couple of problems with it from a public outreach perspective. First, not everyone understands what concentration is, or has context for what the numbers mean. Second, it’s difficult to compare different pollutants to each other, since each pollutant affects people differently depending on concentration. Therefore, concentrations are commonly normalized to some scale, on which multiple pollutants can be compared together and a single “score” covering multiple pollutants given to a city.

Confusingly, there are currently three such scales used to describe Chinese air quality: the US Air Quality Index (AQI), the current/outgoing Chinese Air Pollution Index (空气污染指数, API), and the current/future Chinese Air Quality Index (空气质量指数, AQI). Here are the technical details of each one:

US AQI: In the United States, concentrations are converted to the “Air Quality Index” using breakpoints defined in 40 CFR 58 Subpart G. (Edit 1/13/13: The EPA has just revised these breakpoints, though it hasn’t posted to the CFR yet. New breakpoints shown here and in the graph below.)

Note: the US does not define an AQI above 500. On, if you use the AQI->concentration calculator and input an AQI above 500, it gives an error message.

This means that AQIs reported by the Embassy above 500 are not in accordance with US regulations. My guess is that they linearly projected using the same slope as the 400 –> 500 line.

China API: China’s current but outgoing system of API uses breakpoints described in an old post of mine here. This is officially the current system in place nationwide, though it does not include PM2.5 or ozone.

China AQI: In February 2012 (regulation HJ 633—2012), China defined a new air quality index that includes PM2.5 and ozone. It doesn’t take effect nationwide until 2016, but Beijing and many other cities have already adopted it. The China AQI breakpoints are here:

Note that the Chinese system also does not define an index above 500. This is why the data reported by the BMEMC rail at 500 for AQI. I don’t think they project as the Embassy does.

Let’s do a quick comparison of the PM2.5 cutpoints in the US and in China:

1) The US is more strict at low concentrations.
2) The systems are identical above a concentration of 150 (AQI of 200).
3) Neither system is linear, which is annoying and non-intuitive.
4) It is also very annoying that the numbers are so close (as opposed to a 1-10 index, for example). This means it is very easy to confuse AQI and concentration.

– Concentration is the most accurate way of describing air pollution, but isn’t good for public awareness and comparing multiple pollutants.
– Both the US and China use AQI systems. Both systems go from 0-500, and are not technically defined above 500.
– The US and Chinese systems are identical above an index value of 200 (PM2.5 concentration of 150), but slightly different below this level.
– Because the systems aren’t identical and have different slopes, you have to be very careful when saying something like “PM2.5 is 150.” The meaning of this statement is different depending on if you mean concentration OR US AQI OR Chinese AQI.

Confused yet?

china’s real-time air pollution reporting gaining traction

Sunday, January 13th, 2013

The lead news story on Sina right now is the intense pollution in Beijing and other cities in eastern China. The story is depressing, of course, but I’m encouraged that Sina is reporting numbers from the new Beijing Municipal Environmental Monitoring Center’s real-time reporting system. In this story, they note a maximum PM2.5 concentration reading of 950 ug/m3 in Tongzhou (also here, with graph.) A similar data point making the rounds on weibo and some news outlets is Xizhimen’s maximum PM10 level of 993 ug/m3, again reported based on Beijing’s own monitoring.

Why is this encouraging? Because it represents a much-needed shift away from reporting air quality data from the US Embassy – with all its political and data accuracy concerns – and towards China “owning” its own monitoring and reporting system.

beijing experiences worst pollution in recent memory

Sunday, January 13th, 2013

Beijing’s air pollution levels have been “hazardous” or “beyond index” (by the US Embassy monitor‘s designation) for nearly three days. The city is in the midst of one of its epic, multiple-day extended pollution spells, also known as an “airpocalypse.” So what’s new or different about this one? Let’s take a look from a few angles.

A) The Data
Over the past 24 hours, the US Embassy’s monitor reported a maximum PM2.5 concentration of an incredible 886 ug/m3, certainly the highest I can ever remember. The 24-hour average was reported as 568.5 ug/m3. This 24-hour average can be compared against the Chinese, US, and recommended WHO 24-hour PM2.5 standards, which are 75 ug/m3, 35 ug/m3, and 25 ug/m3, respectively. So, the daily average pollution in Beijing was 7.6, 16.2, and 22.7 times over the standards in China, the US, and the WHO’s recommendations. That is certainly the worst 24-hour period I can remember, though I haven’t been tracking the data recently as closely as I used to.

What about Chinese data? Last year, Beijing began publishing hourly PM2.5 data; real-time monitoring was extended to 74 cities beginning this year. What do the Chinese data say? Well, there are two sites for checking real-time data. The Beijing Environmental Protection Bureau runs its own network of monitors and publishes the results at The user interface is terrible, but I was able to see that the Agricultural Exhibition Center station – not too far from the Embassy – reported a PM2.5 concentration of 699 ug/m3 at 1am on 1/13/13:

The Embassy reported 731 at the same time. These are comparable enough. Not much consolation given the poor state of the air quality, but nice to know that the Chinese real-time PM2.5 data reporting system seems to be tracking the Embassy’s. This is major progress compared to, say, a year ago.

The second monitoring network is run by MEP’s China National Environmental Monitoring Center. The interface for their real-time reporting site,, is also terrible, but if you click through to Beijing you find it currently re-directs data for Beijing to the BJMEMC site. It’s nice to see these groups coordinating their data (which was not always the case), though it’s still not optimal to have the two systems with two interfaces.

Summary: the air quality is awful – perhaps the worst in recent memory. But at least both the US and Chinese government data more or less agree on just how bad it is.

B) The Causes
What’s causing this horrible pollution spell? Although it’s possible we’ll see some detailed studies come out in the coming months that offer some specific or concrete explanation, my guess is that this particular episode was induced by weather patterns. Some are theorizing that it’s due to more coal being burned because of the uncharacteristically cold weather. That’s possible, though I think it is unlikely that this pollution episode is caused primarily by a discrete increase of direct pollutant emissions. Pollution in Beijing is influenced by many factors, but the main ones are:

1) Direct pollutant emissions from factories, vehicles, power plants, etc. across all of Northern China. Beijing has made a lot of progress in recent years in controlling emissions within the city’s municipal boundaries, but the truth is pollution is regional. Whatever happens in all the major provinces around Beijing – Tianjin, Hebei, Inner Mongolia, Shanxi, etc., will effect Beijing. These provinces are developing rapidly – more factories, more power plants, more cars, more coal burning – and it’s making Beijing’s efforts to clean up all that much more difficult. Over the past few weeks, there may have been some increase in emissions due to the severe cold, but I don’t think this discrete increase would have been enough alone to cause a spike of 2 or 5 or 10 times the pollution in Beijing.

2) Secondary pollution. The atmosphere is quite the chemical soup. While direct emissions matter, a lot of air pollution is secondary, meaning that it is caused by directly emitted pollutants interacting with each other in the atmosphere, giving rise to new forms of “secondary” pollution. Much PM2.5 is this secondary pollution. Of course, the longer pollutants are allowed to interact with each other, the crazier and more extreme the secondary pollution will become. This bring me to:

3) Weather. Anyone who has lived in Beijing knows that the primary factor influencing a blue sky day vs. a pea soup sky day is the wind. If there are a few consecutive days where the winds are stagnant – or blowing lightly from the south and trapping pollution against the mountains in northern and northwestern Beijing – the pollution is going to accumulate rapidly. Throw in some increases in direct pollutant emissions from the cold weather, and the chemical soup starts really brewing. The result? Spikes in temporary pollution, in this case all the way above 800. I can’t put my finger on a site right now that can show the air trajectories in northern China over the past few days, but I would be very confident they are showing stagnant air in and around Beijing.

Don’t misinterpret me; I’m not blaming the weather for Beijing’s pollution. Clearly the long-term solution has to be to reduce direct pollutant emissions, as policymakers can’t control atmospheric or weather conditions that give rise to secondary pollution and accumulating pollution spikes. But if you want to point to a discrete reason why there is a spike right now, I think you have to point to weather patterns suboptimal for pollution dispersion, possibly confounded by slight increases in regional direct emissions due to more coal burning for home heating.

C) The Politics
It will be interesting to see the Chinese government’s reaction to this episode. We already have one depressing reaction – Xinhua’s tweet about the “fog” – though no one’s buying it and it’s hard to believe they can get away with this sort of spin much longer. What is more interesting to me is the unfortunate timing of this pollution event. After all, the Chinese government has just racked up a couple of positive wins in air pollution control, specifically:

1) December 5, 2012: MEP last month just released a major regional air quality improvement plan (《重点区域大气污染防治“十二五”规划》), which, for the first time, calls for specific reductions in ambient pollution levels in key cities for a variety of pollutants including PM2.5, and requires cities to develop plans to meet these reduction targets. More on this in a separate post, but it represents a major step forward in comprehensive, integrated, regional air quality management.
2) January 1, 2013: MEP just begain releasing real-time PM2.5 data for 74 cities, a major first step towards data transparency that should be lauded as progress. Although this is only the first step (see Ma Jun’s nice article on this, “We’re winning the air pollution data battle – so what next?“), it is unfortunate that MEP couldn’t bask in a little bit of positive public reaction prior to being slammed with the current pollution crisis.