In Beijing, the AQI is the weather.

The air quality in Beijing can be terrible—although it seems to be getting better.
But is it really getting better? By how much?

photo by Peiheng Yang

The “best” month in terms of air in was August

There were days for which the PM 2.5 level exceeded μg/m3 for hours or more.

Good
Unhealthy
Hazardous
30 μg/m3

for

8 hours or more.
JANUARY
bad days
FEBRUARY
bad days
MARCH
bad days
APRIL
bad days
MAY
bad days
JUNE
bad days
JULY
bad days
AUGUST
bad days
SEPTEMBER
bad days
OCTOBER
bad days
NOVEMBER
bad days
DECEMBER
bad days
PM2.5 > 25 μg/m3 for

Air Quality Index

The weather forecast in Beijing is straightforward: scorching hot or freezing, with a few weeks of spring or fall in between, and only a handful of rainy days. The AQI is a much bigger influence on outside (and inside) conditions.

The AQI, or Air Quality Index, is a single number that roughly communicates how healthy or unhealthy the air is. It's made up of PM10, PM2.5, ozone, carbon monoxide, sulfur dioxide, and nitrogen dioxide. PM2.5—particulate matter with a diameter of 2.5 μm or less—is widely considered the most harmful out of these six, because once inhaled, the lungs can't get rid of these tiny particles; they remain trapped in the airways forever.

The AQI can make or break your day. What could have been a perfect day for lounging at the pool becomes a sad Saturday spent inside, on a 'bad airday'.

What's a bad air day?

The World Health Organization's guideline for PM2.5 is a max annual mean of PM2.5 10 μg/m3, and a 24hr mean of 25 μg/m3.

Annual means in Beijing range from 102 to 35 μg/m3.

Yearly mean PM2.5
2008
2009
'10
'11
'12
'13
'14
'15
'16
'17
'18
'19

The number of days with a daily mean of 25 μg/m3 or above are also plentiful.

Bad days per year (daily mean > 25)
2008
2009
'10
'11
'12
'13
'14
'15
'16
'17
'18
'19

A brief history of Beijing air quality

April 2008 - the start of @BeijingAir

The US Embassy in Beijing installs a rooftop air-quality monitor that automatically tweets out air quality data every hour.

2008 - Olympic car ban

Prior to the 2008 Summer Olympics, Beijing puts several measures in place that aim to restrict the number of cars on its roads: limits based on the first number of license plates, a 75% decrease in the number of newly registered cars, and hiking up the tax on gasoline. A watered down version of these measures stays in place after the Olympics.

July 2009 - Stop the tweets

A Chinese Foreign Ministry official tells the US to halt the Twitter feed, claiming the data is “not only confusing but also insulting” and warming it could lead to “social consequences”.

Nov 2010: Extremely bad air

AQI exceeds 500 for the first time; @BeijingAir calls it crazy bad.

2011

2011 Starts out great, but in February things take a turn for the worse. Global Times uses the word smog for the first time in a headline, instead of the traditional "fog" or "mist". NASA reports massive smog blankets. A compounding factor is temperature inversion: an effect where the air close to the earth's surface is colder than the air above. This effect is stronger in winter, because the nights are longer, and the sun is not as strong. The fact that Beijing is surrounded by mountains further intensifies the problem. Finally, Beijing relies heavily on coal-burning for heat during the winter. A toxic combination, shall we say. The end of 2011 marks another bad episode in Beijing air quality. 200 Flights cancelled. Local news outlets are putting the pressure on the government to admit that the air is problematic.

2012 - local data incoming

Under pressure from local and foreign sources, Beijing starts to release its own PM2.5 data. Definitely a more balanced year, 2012 starts off with its worst month. The summer months are the best so far. Similar to 2011 and 2012, from October things start to get worse again.

Jan 2013 - Airpocalypse

Oof. That big black spot in January? That's airpocalypse. Back in 2013, China experienced its worst smog outbreak since 1961.

Sept 2013 - Government steps up

In September, State Council unveils Action Plan for the Prevention and Control of Air Pollution. Apparently, Xi JinPing said: "green mountains and clear water are equal to mountains of gold and silver." 2014 looks worse than 2013. What's going on? Moderate spring and summer vs extreme fall and winter trend is continuining. The last two months of the year looks like it's improving.

0
0
2008
0
0
2009
0
0
2010
0
0
2011
0
0
2012
0
0
2013
0
0
2014
0
0
2015
0
0
2016
0
0
2017
0
0
2018
0
0
2019
days with mean > 25
annual mean (μg/m3)
PM2.5 (μg/m3)
0 - 50 (μg/m3)
50 - 100
100 - 150
150 - 200
250 - 300
300+