Improvement in air quality also over Europe, learning for global heating?

The anti-corona measures that were implemented by many European countries in the course of March led to a lockdown of cities, regions and even countries. With the nomination to an exclusion area by 10 March 2020 the territory of Italy became the first country to be locked. Others followed soon thereafter. Meanwhile almost every country in Europe is affected by measures to curb the spread of the corona infection. The implemented actions led to a significant reduction of transport (on the road and in the air), an extensive ban of trade and a shut down of industries resulting in a hefty diminished demand for energy and fossil fuels.

Similar to China, new data based on observations from the Copernicus Sentinel-5P satellite, operated by ESA, have shown significant reductions of nitrogen dioxide concentrations over several urban regions across Europe, among them the metropolitan areas of Paris, Milan and Madrid. The maps at hand compare the average nitrogen dioxide concentration of March 2019 with the NO2 concentration from 14-25 March 2020 for the mentioned agglomeration areas. The 10 days time frame in March 2020 is necessary to average out meteorological variability and see the human induced changes in the atmosphere. Hence, the substantial decrease of NO2 concentration can be explained by the anti-corona actions. Considering that the range of anti-corona measures was realized gradually starting around mid March, the atmospheric response to the decreasing emissions is quick.

Nitrogen dioxide concentrations over Italy in March 2019 (averaged) in the left panel and from 14 – 25 March 2020 in the right panel. Source: ESA

Nitrogen dioxide concentrations over France in March 2019 (averaged) in the left panel and from 14 – 25 March 2020 in the right panel. Source: ESA

Nitrogen dioxide concentrations over Spain in March 2019 (averaged) and from 14 – 25 March 2020. Source: ESA

The reduced burning of fossil fuels in China has cut carbon dioxine emissions by 25% over a four-week-period resulting in cleaner air at relatively low economic costs (The Guardian). Considering the drop of CO2 emissions in Europe, the United States and other parts of the world might be possible that 2020 will register the first fall of CO2 emissions after the financial crisis in 2008. However, in the course of the corona pandemic political and corporate authorities have been taking radical emergency measures on the advice of scientists to protect human beings. It will be crucial that related to global heating politics act with similar decisiveness and purposefulness on behalf of the human population.

Articles: Guardian, Carbon Brief, Euractiv (German)

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Better air quality over China due to anti-corona actions

Three moths ago nobody would have considered a shut down of transport, local businesses and industrial facilities as a consequence of the fight against the corona virus possible. Authorities all over the world have come up with plans to delimit and cease daily activities to prevent the corona virus from spreading further. This has led to quarantine regulations in China starting in February and many European countries following in March.

Highly perceptible for everyone is the reduction of public transport and as a consequence of the limitations to daily life also the private one. On the road from Klagenfurt to Munich last Saturday I counted less than 15 private cars on a stretch of around 350km! Airlines are reducing or ceasing regular flights, among them Emirates (cancellation of all passenger flights by 25th March), Etihad (cancellation of all passenger flights by 25th March), Ryan Air (grounding of most flights by 24th March), Lufthansa (operating return timetable mostly), Austrian Airlines (cancellation of all passenger flights by 18th March) and many more.

Screenshot showing flights over Europe on 26th March at 19:45. The flight traffic is significantly reduced compared to the regular flight traffic. Source: Flightradar24

The established regulations have an effect on the quality of air: NASA and ESA pollution monitoring satellites have shown a significant reduction in atmospheric nitrogen dioxine (NO2) over China in February 2020. – NO2 is created by burning fossil fuels, for instance in combustion engines or power plants, which is linked to the initially mentioned actions. It is highly poisonous and in the United States classified as an extremely harzadous substance (Section 302 of the U.S. Emergency Plannning and Community Right-to-Know Act (42 U.S.C. 11002)), causing respiratory symptoms and diseases (source).

In the figure below, the left panel shows the concentration of NO2 across China from January 1 – 20 before anti-corona virus actions taken. The panel on the right side exhibits NO2 concentrations across China in the time of February 10 – 25 during the quarantine. The comparison reveals a significant drop in NO2 over wide parts of the country. According to Fei Liu, air quality researcher at NASA’s Goddard Space Flight Center, such a dramatic drop-off over large areas was never observed so far (source).

Nitrogen dioxine measured by TROPOMI instument on Sentinel-5P satellite over China between 1 January and 25 February 2020. Source: NASA Earth Observatory

The drop in nitrogen dioxine also coincides with the Lunar New Year festivities in China (last week of January until early February) and parts of Asia. Past observations reveal that air pollution during this time usually sinks as a consequence of closing factories and businesses. However, this years’s NO2 drop is more than a “holiday effect”, which is also undermined by the numbers of NO2 concentrations compared to the last years.

Simulation videos about the change of nitrogen dioxine concentration over China and most recently also in Northern Italy can be observed by clicking the corresponding links. The videos are contributed by ESA.

EO satellites

The presented NO2 concentrations were measured by the Tropospheric Monitoring Instrument (TROPOMI) on board of the Copernicus Sentinel-5P satellite, operated by ESA.

Sentinel-5 Precursor satellite is the first of atmospheric composition Sentinels and was launched on 13th October 2017. It’s life time is planned to last seven years. To obtain an impression about the instrument’s capability, the measurements made by TROPOMI and offered as Level-2 products are listed as follows: UV aerosol index, aerosol layer height (mid level pressure), carbon monoxide (CO), cloud (fraction, albedo, top pressure),  formaldehyde (HCHO, total column), methane (CH4, total column), nitrogen dioxide (NO2, total column), ozone profiles, sulphur dioxide (SO2, total column), ozone (O3, total column), troposheric ozone (troppsheric column).

The Ozone Monitoring Instrument (OMI) on board of NASA’s Aura satellite has made similar measurements as the one shown by ESA’s Sentinel-5P.

One man’s joy is another mans sorrow

The corona pandemic has shown that dramatic actions taken by authorities can be realized within short time. Some of the taken actions are climate relevant and have a positive impact on the environment such as air quality within short time. This is undermined by the presented example of nitrogen dioxine concentration recorded by the Sentinel-5P satellite.

This pandemic makes us aware that we are adaptable to changing conditions and able to take actions in order to delimit the spread of a virus and in future – hopefully – also to reduce the effects of climate change.

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