Satellite images show reductions in air pollution over European cities

Satellite images show massive reductions in air pollution over Paris, Madrid and Milan following lockdown measures to slow the spread of the deadly coronavirus in Europe

  • Nitrogen dioxide and micro particle levels have fallen in London since mid Feb
  • Air particle levels are about half of what would be recorded this time of the year 
  • London Air Quality Network data suggests it’s due to lower levels of road traffic
  • Nitrogen dioxide pollution is also falling in other major UK cities, data suggests
  • Coronavirus symptoms: what are they and should you see a doctor?

Satellite images from the European Space Agency show a massive drop in air pollution levels across European cities due to coronavirus isolation measures.

New data captured by the ESA Copernicus Sentinel-5P satellite shows a strong reduction in nitrogen dioxide concentrations over major European cities.

The change in the amount of NO2 in the atmosphere is particularly stark in Paris, Milan and Madrid, according to the ESA. 

The coronavirus has been spread around the world and to combat this spread and ease demand on health services countries have gone into lockdown.

Copernicus has mapped air pollution levels across Europe since the outbreak of the virus and found a ‘significant drop’ coinciding with new lockdown measures.

The new maps shared by the European Space Agency show a dramatic difference in NO2 levels across Spanish cities including Madrid and Barcelona

The change in the amount of NO2 in the atmosphere is particularly stark in Paris, Milan and Madrid (pictured), according to the ESA

The images show a dramatic difference in NO2 levels across all European cities, particularly in Spain, France and Italy coinciding with the lockdown measures.

It matches similar figures from the London Air Quality Network that showed a sharp drop in air pollution levels over the UK capital city.

This is due to a notable drop in traffic levels on the streets of cities across Europe. 

GPS maker TomTom said the percentage of roads congested with traffic in London dropped from 71 per cent this time in 2019 to just 15 per cent yesterday. 

The UK capital’s levels of ultra-fine particulate matter, known as PM2.5, are currently around half that would be normally recorded at this time of year.

This matter is produced in a large part from vehicles and burning fossil fuels.  

Scientists from the Royal Netherlands Meteorological Institute (KNMI) have been using data from Copernicus Sentinel-5P satellite to monitor both weather and pollution over Europe. 

On the left of this picture is the level of NO2 over France in March 2019 and you can see a drop in the number of dark red areas from the left hand picture to the March 2020 image on the right

A volunteer of the Ordre de Malte (‘Order of Malta’), the French branch of the Malteser International aid agency, speaks with a homeless person on a street in Paris, France, 27 March 2020. Since 17 March, all of France remains under a national lockdown

The satellite images show nitrogen dioxide concentrations from 14 to 25 March 2020, compared to the monthly average of concentrations from 2019. 

Henk Eskes, from KNMI, explains why these dates were chosen, ‘The nitrogen dioxide concentrations vary from day to day due to changes in the weather. Conclusions cannot be drawn based on just one day of data alone. 

‘By combining data for a specific period of time, 10 days in this case, the meteorological variability partly averages out and we begin to see the impact of changes due to human activity,’ Eskes said.

‘The chemistry in our atmosphere is non-linear. Therefore, the percentage drop in concentrations may differ somewhat from the drop in emissions. 

‘Atmospheric chemistry models, which account for daily changes in weather, in combination with inverse modelling techniques are needed to quantify the emission based on the satellite observations.’

The latest images and data focus on Italy, Spain and France but they are working on studying data for parts of northern Europe including the UK and Netherlands. 

‘New measurements from this week will help to assess the changes in nitrogen dioxide over northwest Europe,’ ESA said.  

The multi-national space agency did confirm that levels of the pollutants over London are significantly lower than in March 2019.   

European Environment Agency (EEA) data shows that air pollutant concentrations in Rome and Milan have dropped by 50 per cent, while a Paris air quality monitoring agency recorded up to a 30 per cent decline in pollution. 

The KNMI team, in collaboration with scientists worldwide, have started to work on a more detailed analysis using ground data, weather data and inverse modelling to interpret the concentrations observed.

They are using this data to estimate the influence of the shutdown measures. 

‘For quantitative estimates of the changes in the emissions due to transportation and industry, we need to combine the Tropomi data from the Copernicus Sentinel-5P satellite with models of atmospheric chemistry,’ said Henk.

The starkest change in NO2 levels can be seen over northern Italy – including Milan – where some of the highest number of coronavirus cases have hit. The left image is 2019 and the right is 2020

People walk in an empty street, during a lockdown against the spread of coronavirus disease (COVID-19) in Milan, Italy. It went into a lockdown to slow the spread of the disease

‘These studies have started, but will take some time to complete.’  

As daily life grinds to a halt in the UK due to restricted movement to control the spread of COVID-19, air quality has improved due to a sharp reduction in traffic. 

These promising early signs suggest air pollution could be falling across UK cities while the pandemic goes on. 

‘Air quality has started to improve in many UK cities, mirroring what has been seen in other countries that have restricted travel and levels of outdoor activity,’ said Professor Alastair Lewis, from the National Centre for Atmospheric Science, University of York.

‘This is primarily a consequence of lower traffic volumes, and some of the most clear reductions have been in nitrogen dioxide, which comes primarily from vehicle exhaust. 

‘However fine particles (PM2.5) have also reduced significantly.


PM is a mixture of solid particles and liquid droplets found in the air.

They are created from a variety of sources, including traffic, construction sites, unpaved roads, fields, smokestacks or fires.

Most particles form in the atmosphere as a result of reactions of chemicals such as sulfur dioxide and nitrogen oxides. 

Some PM, such as dust, dirt, soot, or smoke, is large or dark enough to be seen with the naked eye. 

Other PM is so small it can only be detected using an electron microscope. 

PM2.5 – of diameters that are generally 2.5 micrometers and smaller – differ from PM10 – 10 micrometers and smaller.

Source: US EPA 

‘In London for example, PM2.5 is noticeably lower than would be expected for this time of year at the roadside, and these reductions stretch through into the suburbs as well.’  

Professor Lewis said it’s especially important to consider how PM2.5 levels have changed compared to what is normally seen at this time of year. 

‘Air pollution is noisy, changing with weather and so on,’ he said.  

‘It’s really best to compare where we are now against where we might have expected to be based on previous years.’

London Air Quality Network, a King’s College London project, comprises more than 100 continuous monitoring sites in the majority of London’s 33 boroughs. 

The data shows that PM2.5 levels in the capital are currently about half those seen on average from 2015 to 2019, as measured in micrograms (one-millionth of a gram) per cubic meter air (µg/m3). 

These fine inhalable particles have diameters that are generally 2.5 micrometers and smaller.

The average human hair is about 70 micrometers in diameter – making PM2.5 about 30 times larger than the largest fine particle. 

It is not yet clear what the health impacts of reductions in air pollution, which causes an estimated 40,000 early deaths in the UK each year, will be. 

Air pollution is linked to health problems including stroke, heart disease, lung cancer and disease, and respiratory diseases and infections, as well as stunting the growth of children’s lungs. 

Pollutant drops in major European cities: The numbers published by the European Environment Agency

Milan, Italy

The average concentrations of NO2 for the past four weeks have been at least 24% lower than four weeks earlier this year. The average concentration during the week of 16-22 March was 21% lower than for the same week in 2019.

Bergamo, Italy

Here, there has been a constant decline in NO2 pollution over the past four weeks. The average concentration during the week of 16-22 March was 47% lower than for the same week in 2019.

Rome, Italy

The average NO2 concentrations for the past four weeks were 26-35% lower than for the same weeks in 2019.

Barcelona, Spain

The average NO2 levels went down by 40% from one week to the next. Compared with the same week in 2019, the reduction was 55%.

Madrid, Spain

The average NO2 levels went down by 56% from one week to the next. Compared with the same week in 2019, the reduction was 41%.

Lisbon, Portugal

The average NO2 levels went down by 40% from one week to the next. Compared with the same week in 2019, the reduction was 51%.

Geospatial imagery analytics firm Descartes processed data from the Sentinel-5P satellite and compared it with March 12-22 of last year, showing that levels of NO2 in London have dipped dramatically year-on-year



Carbon dioxide

Carbon dioxide (CO2) is one of the biggest contributors to global warming. After the gas is released into the atmosphere it stays there, making it difficult for heat to escape – and warming up the planet in the process. 

It is primarily released from burning fossil fuels such as coal, oil and gas, as well as cement production. 

The average monthly concentration of CO2 in the Earth’s atmosphere, as of April 2019, is 413 parts per million (ppm). Before the Industrial Revolution, the concentration was just 280 ppm. 

CO2 concentration has fluctuated over the last 800,000 years between 180 to 280ppm, but has been vastly accelerated by pollution caused by humans. 

Nitrogen dioxide 

The gas nitrogen dioxide (NO2) comes from burning fossil fuels, car exhaust emissions and the use of nitrogen-based fertilisers used in agriculture.

Although there is far less NO2 in the atmosphere than CO2, it is between 200 and 300 times more effective at trapping heat.

Sulfur dioxide 

Sulfur dioxide (SO2) also primarily comes from fossil fuel burning, but can also be released from car exhausts.

SO2 can react with water, oxygen and other chemicals in the atmosphere to cause acid rain. 

Carbon monoxide 

Carbon monoxide (CO) is an indirect greenhouse gas as it reacts with hydroxyl radicals, removing them. Hydroxyl radicals reduce the lifetime of carbon dioxide and other greenhouse gases. 


What is particulate matter?

Particulate matter refers to tiny parts of solids or liquid materials in the air. 

Some are visible, such as dust, whereas others cannot be seen by the naked eye. 

Materials such as metals, microplastics, soil and chemicals can be in particulate matter.

Particulate matter (or PM) is described in micrometres. The two main ones mentioned in reports and studies are PM10 (less than 10 micrometres) and PM2.5 (less than 2.5 micrometres).

Air pollution comes from burning fossil fuels, cars, cement making and agriculture 

Scientists measure the rate of particulates in the air by cubic metre.

Particulate matter is sent into the air by a number of processes including burning fossil fuels, driving cars and steel making.

Why are particulates dangerous?

Particulates are dangerous because those less than 10 micrometres in diameter can get deep into your lungs, or even pass into your bloodstream. Particulates are found in higher concentrations in urban areas, particularly along main roads. 

Health impact

What sort of health problems can pollution cause?

According to the World Health Organization, a third of deaths from stroke, lung cancer and heart disease can be linked to air pollution. 

Some of the effects of air pollution on the body are not understood, but pollution may increase inflammation which narrows the arteries leading to heart attacks or strokes. 

As well as this, almost one in 10 lung cancer cases in the UK are caused by air pollution. 

Particulates find their way into the lungs and get lodged there, causing inflammation and damage. As well as this, some chemicals in particulates that make their way into the body can cause cancer. 

Deaths from pollution 

Around seven million people die prematurely because of air pollution every year. Pollution can cause a number of issues including asthma attacks, strokes, various cancers and cardiovascular problems. 


Asthma triggers

Air pollution can cause problems for asthma sufferers for a number of reasons. Pollutants in traffic fumes can irritate the airways, and particulates can get into your lungs and throat and make these areas inflamed. 

Problems in pregnancy 

Women exposed to air pollution before getting pregnant are nearly 20 per cent more likely to have babies with birth defects, research suggested in January 2018.

Living within 3.1 miles (5km) of a highly-polluted area one month before conceiving makes women more likely to give birth to babies with defects such as cleft palates or lips, a study by University of Cincinnati found.

For every 0.01mg/m3 increase in fine air particles, birth defects rise by 19 per cent, the research adds. 

Previous research suggests this causes birth defects as a result of women suffering inflammation and ‘internal stress’. 

What is being done to tackle air pollution? 

Paris agreement on climate change

The Paris Agreement, which was first signed in 2015, is an international agreement to control and limit climate change. 

It hopes to hold the increase in the global average temperature to below 2°C (3.6ºF) ‘and to pursue efforts to limit the temperature increase to 1.5°C (2.7°F)’.

Carbon neutral by 2050 

The UK government has announced plans to make the country carbon neutral by 2050. 

They plan to do this by planting more trees and by installing ‘carbon capture’ technology at the source of the pollution.

Some critics are worried that this first option will be used by the government to export its carbon offsetting to other countries.

International carbon credits let nations continue emitting carbon while paying for trees to be planted elsewhere, balancing out their emissions.

No new petrol or diesel vehicles by 2040

In 2017, the UK government announced the sale of new petrol and diesel cars would be banned by 2040. 

From around 2020, town halls will be allowed to levy extra charges on diesel drivers using the UK’s 81 most polluted routes if air quality fails to improve.

However,  MPs on the climate change committee have urged the government to bring the ban forward to 2030, as by then they will have an equivalent range and price.

The Paris Agreement, which was first signed in 2015, is an international agreement to control and limit climate change. Pictured: air pollution over Paris in 2019.

Norway’s electric car subsidies

The speedy electrification of Norway’s automotive fleet is attributed mainly to generous state subsidies. Electric cars are almost entirely exempt from the heavy taxes imposed on petrol and diesel cars, which makes them competitively priced.

A VW Golf with a standard combustion engine costs nearly 334,000 kroner (34,500 euros, $38,600), while its electric cousin the e-Golf costs 326,000 kroner thanks to a lower tax quotient. 

Criticisms of inaction on climate change

The Committee on Climate Change (CCC) has said there is a ‘shocking’ lack of Government preparation for the risks to the country from climate change. 

The committee assessed 33 areas where the risks of climate change had to be addressed – from flood resilience of properties to impacts on farmland and supply chains – and found no real progress in any of them.

The UK is not prepared for 2°C of warming, the level at which countries have pledged to curb temperature rises, let alone a 4°C rise, which is possible if greenhouse gases are not cut globally, the committee said.

It added that cities need more green spaces to stop the urban ‘heat island’ effect, and to prevent floods by soaking up heavy rainfall. 

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