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Covid-19: Satellite data reveal global air pollution levels plummeting

There is a climate consequence to this outbreak.

Copernicus Sentinel data (2019-20), processed by KNMI/ESA

Since the outbreak of COVID-19, the world has essentially hit the pause button in order to deal with the pandemic.

As a result, global air pollution levels have plummeted over the past six weeks as factories shut down, traffic slows down and businesses are forced to close. And the stark, before and after effects can be seen from space.

New satellite imagery collected by the European Space Agency (ESA) has shown air pollution levels significantly drop across Europe and China.

In a visualization released Friday, March 27, ESA used data collected by its Copernicus Sentinel-5P satellite to show how air pollution levels over Paris, Madrid, Rome, Italy, and China have changed from December to March.

This is how dramatic the difference is in the skies above Europe, over the course of just one week:

Levels of nitrogen dioxide can be seen decreasing over time in this ESA animation.ESA

The above animation reveals the incredible reduction in levels of nitrogen dioxide above Madrid, Spain during the period of March 14-25 of this year, compared to that same period the year before. Nitrogen dioxide is one of the most abundant greenhouse gas pollutants.

This normally bustling city went into lockdown mid-March, as more than 1,000 people have lost their lives to the novel coronavirus in Madrid alone.

Like other countries in Europe, France has also officially gone into lockdown this week. There are more than 22,000 confirmed cases in France, which makes it the fourth highest case count in Europe.

Satellite imagery reveal a drop in air pollution over France.ESA

The before-and-after images shown above were put together using satellite data recorded over France during the same period, between March 14-25, 2020 and 2019.

The same data were collected for Italy, too:

A single week of emissions over Italy, demonstrating the dramatic drop in nitrogen dioxide levels.ESA

Global consequences

The new visualizations come in the wake of another ESA video, which reveals how satellite observations show a significant decline in nitrogen dioxide levels over China since the outbreak began in December, 2019.

The data revealed a 20-30 percent reduction in fine particle matter compared with the previous three years.

As the video shows, nitrogen dioxide emissions begin to decline in late January, which coincided with a government-imposed lockdown of certain regions of the country. On January 23, the Chinese government imposed a lockdown in Wuhan and other surrounding cities in order to help stop the spread of the novel coronavirus.

The lockdown shut down factories, closed off roads and restricted people to their homes.

This before-and-after image shows nitrogen dioxide gas emissions over China between January 1 - February 25, 2020.NASA/ESA

"As nitrogen dioxide is primarily produced by traffic and factories, it is a first-level indicator of industrial activity worldwide," Josef Aschbacher, ESA’s Director of Earth Observation Programmes, said in a statement.

But worryingly, the video shows nitrogen dioxide levels are beginning to rise again in early March, as restrictions eased across some Chinese cities as the number of new cases decreases over time. Only time will tell if they will reach pre-coronavirus levels, or surpass them, as industry ramps back up.

The video echoes a similar trend in the data observed over Italy, where there is also a significant outbreak of COVID-19 and a country-wide shutdown in force.

As in China, nitrogen dioxide emissions started to decline in late January as the state started to lockdown industry-heavy areas of the country.

In order to help stop the spread of the virus, Italy’s Prime Minister Giuseppe Conte recently extended the lockdown from northern Italy to the entire country. Italy has the most cases out of all European countries, with more than 9,000 diagnosed cases at the time of writing.

This video was also captured by ESA's Copernicus Sentinel-5P satellite, from January 1 to March 11, showing a view of all of Europe. The drop in air pollution is most precipitous over northern Italy.

Eyes in the sky

ESA is keeping an eye on other parts of Europe, including the Netherlands and the United Kingdom, to monitor how their air pollution levels change over time as well.

The stark before-and-after results of the lockdown in the UK can be seen in these visualizations created by The Guardian in tandem with data from global space agencies.

As the coronavirus pandemic takes effect in each country, air pollution levels drop precipitously from 2019 levels. You can see the visualizations here.

The World Health Organization (WHO) recently declared COVID-19 as a global pandemic. As of March 26, the disease has claimed the lives of more than 25,000 people worldwide.

Aside from the virus' devastating effects on our lives, it has also highlighted how a slight decrease in human activity may have dramatic influence another looming threat to people's health. Air pollution kills around 7 million people per year, according to the WHO.

Together, the animations provide some indication of how ongoing social distancing and working-from-home habits currently being implemented in some cities in the United States may have on the levels of air pollution, for example in normally bustling cities like New York or San Fransisco.

Perhaps by the time things return to semi-normality, we will all be going out to clearer skies, and fresher air than before.