Nitrogen Dioxide Ramping Up Again Over China

From United space in Europe

ESA / Applications / Observing the Earth / Copernicus / Sentinel-5P

Recent data have shown a decline of air pollution over northern Italy coinciding with its nationwide lockdown to prevent the spread of the coronavirus (COVID-19). This new map shows the variation of nitrogen dioxide emissions over China from December to March – thanks to the Tropomi instrument on board the Copernicus Sentinel-5P satellite.

As news of the coronavirus broke out in the Hubei province, China, in late December 2019, stricter measures were put in place. As a result, by late January, factories were closed and streets were cleared as Chinese authorities had ceased daily activities to stop the spread of the illness.

This led to the dramatic reduction in nitrogen dioxide emissions – those released by power plants, industrial facilities and vehicles – in all major Chinese cities between late-January and February. The drop in emissions also coincided with Lunar New Year celebrations, which usually sees a similar drop in emissions each year.

The Copernicus Atmosphere Monitoring Service (CAMS) observed a decrease of fine particulate matter – one of the most important air pollutants – in February 2020 compared to the previous three years. By combining satellite observations with detailed computer models of the atmosphere, their studies indicated a reduction of around 20-30% in surface particulate matter over large parts of China.


Nitrogen dioxide emissions over China
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As the coronavirus epidemic eases in China, many provinces have downgraded their emergency response levels. Schools, factories and other public spaces are starting to re-open and workers are gradually returning to their jobs.

This animation, using data from the Copernicus Sentinel-5P satellite, shows the nitrogen dioxide emissions from 20 December 2019 until 16 March 2020 – using a 10-day moving average. The drop in emissions in late-January is visible, coinciding with the nationwide quarantine, and from the beginning of March, the nitrogen dioxide levels have begun to increase.

Josef Aschbacher, ESA’s Director of Earth Observation Programmes, says, “Satellites offer a unique vantage point to monitor the health of our planet. Sentinel-5P is one of seven Copernicus satellites in orbit today. It currently provides the most accurate measurements of nitrogen dioxide and other trace gases from space.

“As nitrogen dioxide is primarily produced by traffic and factories, it is a first-level indicator of industrial activity worldwide. What is clearly visible is a significant reduction of nitrogen dioxide levels over China, caused by reduced activity due to COVID-19 restrictions, but also the Chinese New Year in January.”

He continues, “The Copernicus programme is a perfect example of how space serves all European citizens by combining the political strength of the EU with the technical excellence of ESA.”

Bringing air pollution into focus

Bringing air pollution into focus

Claus Zehner, ESA’s Copernicus Sentinel-5P mission manager, comments, “We can certainly attribute a part of the nitrogen dioxide emission reduction to the impact of the coronavirus. We currently see around a 40% reduction over Chinese cities, however these are just rough estimates, as weather also has an impact on emissions.

“We are conducting a detailed scientific analysis which will soon provide more insights and quantified results in the following weeks and months.”

The Copernicus Sentinel-5 Precursor mission, also known as Sentinel-5P, is dedicated to monitoring air pollution by measuring a multitude of trace gases as well as aerosols – all of which affect the air we breathe.

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Stan Sexton
March 19, 2020 6:07 pm

How about the level of sulphur dioxide emissions from cremation? They were very high just a couple weeks ago.

Robert of Texas
Reply to  Stan Sexton
March 19, 2020 6:59 pm

Why would cremation generate a lot of sulfur dioxide? The fuel used? Or was this a jest?

Coal contains a LOT of sulfur compared to an animal. Burning coal without scrubbing the outflow would easily generate hundreds of times the amount of sulfur generated by burning bodies. How does one pick one source over the other?

Reply to  Robert of Texas
March 19, 2020 8:00 pm

There were claims of being able to see crematoriums around Wuhan a few weeks ago based on their SO2 emissions from pollution monitoring.

You’re probably correct that the fuel would be the primary source, which is corroborated by the paper linked below. The normal body has about 3000 ppm mass sulfur though. Individuals like Loydo and Bindidon would undoubtedly contain much more being as how they are full of it. It’s likely that during the crisis, no flue gas cleanup was used.!po=34.3750

Reply to  Robert of Texas
March 19, 2020 11:43 pm

A possibly signature of cremations could be mercury.
If people have/had amalgam fillings a lot of mercury is going to be vaporized.

Reply to  GregK
March 20, 2020 7:35 am

They don’t collect and recycle tooth feelings? Why not?

Reply to  niceguy
March 20, 2020 8:54 am

Against tooth fairy rules. Feelings are to be held and not recycled, unless they are golden.

Reply to  Stan Sexton
March 20, 2020 7:34 am

What about treated teeth?
Pollution hazard?

How many Chinese citizens have peacemakers?
Some time ago an accident occurred in France due to a peacemaker nobody apparently knew about.

Walter Sobchak
Reply to  Stan Sexton
March 20, 2020 7:43 am

In November, I was in Varanasi (Benares) India where they cremate bodies 24/7 on the ghats (steps) along the banks of the Ganges. Air quality was bad, but not as bad as the air quality in Delhi which is due to motorbikes and tuk-tuks.

Robert of Texas
March 19, 2020 7:02 pm

If “we” are measuring it, then I believe it as long as no climate scientists are involved. If China is reporting it, then I don’t.

I am still doubtful that they have no new infections in this area. Me thinks the government is covering up the real statistics…I just hope they have it under control.

March 19, 2020 8:16 pm

It’s said that China’s politburo was made aware of this and ordered everyone back to work so as not to spoil productivity and the economy. The reaction was to turn on all the machinery and just let it run, by itself, with no operators or production. Like when they were in the throws of famine they just reported higher crop yields to save face and life. Disappointing superiors leads to drastic consequences.

Joe Adams.
March 19, 2020 9:28 pm

Interesting that the global shutdown of industry and airflights has not been reported to have increased global temperatures as per the Global Dimming theory brought out by the alarmists as the excuse for why the world wasn’t heating the way they said it should be.
One of their “proofs” for dimming’s effect was broadcast as the fact that the US had a 3°C or 3°F increase in temperature during the days that flights were shutdown after 9/11.
Looks like the rise in temperature after 9/11 was what it actually was. Weather.

Keen Observer
March 19, 2020 9:34 pm

When he said, “Weather has an effect on emissions,” I’m sure he meant to say “climate” does…

March 19, 2020 10:26 pm

Why only a 20-30% reduction? The power plants still running?

March 20, 2020 1:14 am

At least they made no attempt to confound CO2 with airborne pollution. That must be a world first.

Carl Friis-Hansen
March 20, 2020 1:50 am

As stated in the article, the weather plays a role too.
If you look at the pictures in the NASA article, a comparison between 2019 and 2020 seems troublesome, as the base level is so different between the two years. Let us call it under exposure in 2020, thus it would be very difficult to see the actual change, throughout 2020, of next to nothing.
If NASA attempted to demonstrate delta pollution for the first months of 2020, they should first adjust the exposure level to near equal levels for the two years, even if the absolute level was far apart.

March 20, 2020 8:17 am

What are people’s views on the most up to date global CO2 levels????
China has been under lockdown for 3 months and many other places following on…
We have had mass and very abrupt changes in our economies …
Yet this data that is measured to .00 of the ppm is showing no change…
Does this unique historical situation we are now in finally prove that we have no control over CO2 levels and the vast vast amount comes from natural sources…
Thoughts please ???

Carl Friis-Hansen
Reply to  TimBo
March 20, 2020 12:03 pm

Really interesting point TimBo.
Looking at last month’s graph, there is not much of a trend.
We will watch this space.

Reply to  TimBo
March 20, 2020 2:21 pm

March 20, 2020 at 8:17 am

I wonder if NASA or ESA still has any satellites recording CO2 levels.
Does OCO still exist? I think I read somewhere it is no longer operational.

Joel O'Bryan
March 20, 2020 10:01 am

Hubei province (Wuhan region) stills shows quite depressed NO2 levels.

Steve Z
March 20, 2020 2:46 pm

[QUOTE FROM ARTICLE]”We currently see around a 40% reduction over Chinese cities, however these are just rough estimates, as weather also has an impact on emissions.”

Indeed! Nitrogen oxides can react with diatomic oxygen (O2) in the air to form ozone (O3) and diatomic nitrogen (N2), with energy supplied by sunlight. There are many such reactions in a very complex balance, but most of them require sunlight as an energy source to generate free radicals, which propagate the reaction. Like most parts of the Northern Hemisphere, the sun angle near Beijing is higher in March than in December, so some of the nitrogen oxides could have been reacted away to form ozone.

The satellites can only measure concentrations of pollutants, not emission rates. The concentration of any pollutant represents the time integral of (emission rate – rate of destruction by reaction) over recent history. In order to back out emission rates, there must be some estimate of the rate of destruction by reaction, to be added to the time derivative of concentration.

March 28, 2020 3:38 am

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