COVID-19 has put the world on pause. As cities across Europe implement lockdown measures, the impact on pollution is a breath of fresh air.
The WHO began surveilling Europe for COVID-19 on January 27th, 2020. As the number of cases ticked upward, cities and countries across the continent implemented measures for containment — at first, reluctantly, then swiftly and out of necessity. The magnitude of the resultant social and economic impact is difficult to overstate and will ripple into the future in somewhat predictable but largely unknowable ways. Data on how air quality has changed, however, tells a clear story of positive difference.
It follows that when travel, even on local scales, is greatly reduced, there would be a decrease in emissions. But what does this look like — how big is the change and how immediate is the effect?
A visual analysis of measurements of NO2 taken in six cities across Europe shows how concentrations of this gas have changed post-lockdown. NO2, a product of the combustion of fuel, is an emission for which the two most common sources are vehicles and power plants. The overall impact for each locale varies depending on factors which range from the more abstract (e.g. community ethos and behavioral tendencies) to numerical observation (e.g. concentration of emissions preceding lockdown).
In general, Europe has made concerted efforts to reduce its environmental footprint and succeeded. Supporting this, plotting daily levels of NO2 from January 1st through April 30th shows that there is an observable reduction from 2018 to 2019, and from 2019 to 2020. There is a wavelike up-down periodicity which appears to occur year after year, perhaps indicating traffic fluctuations that correlate to days of the week. Many such relational and pattern-based observations surely exist, but the focus of this analysis is what occurs at and as a result of lockdown.
On March 9th, Milan became the first major European city to implement lockdown measures. Copenhagen followed suit on March 13th, with Madrid close on its heels on March 14th. Paris went into lockdown on March 17th, and then London on the 23rd. Stockholm did not instate any official lockdown.
It is clearest in the case of Madrid, and nearly as noticeable for Milan and Paris, that after issuance of recommendations for extreme social distancing, the level of NO2 sees an immediate and marked drop that is sustained. Copenhagen and London show a slight, perhaps contestable reduction in concentrations of NO2, while Stockholm, the only city of this set which did not implement lockdown, exhibits no real difference in its NO2 trends for January to the end of April.
The visualizations below show daily range and average NO2 concentrations from January through April, 2018-2020. Use the filters to highlight specific cities, years, and metrics.
Light gray shows 2018 and dark gray shows 2019 daily ranges of NO2 pollution concentrations.
The following story highlights air quality patterns in Madrid, Spain.
On January 31st, Spain confirmed its first COVID-19 case in La Gomera, Canary Islands. By mid-February, at least two different strains of the virus were circulating in Spain.
The blue gradient shows 2020 daily ranges of NO2 concentrations.
On March 13th, Prime Minister Pedro Sánchez announced a national state of alarm. Spain's lockdown went into effect two days later.
The post-lockdown drop in Madrid's NO2 is immediate and sustained through April.
This post-lockdown reduction in concentration of NO2 is further supported by comparing hourly data from one day that falls before and one that falls after lockdown. Starting with two Mondays (to eliminate the suspected variance in traffic trends between days of the week), a comparison of the hourly averages over the course of a day shows that at almost every hour, there is a reduction in concentrations of NO2. As would be expected, this bolsters the conclusion that there is a reduction in emissions. This temporal scale also makes it possible to observe the emissions peaks in the morning and evening, and these visible trends which map to rush hours lend additional insight, primarily into how responsive NO2 concentrations are to the number of cars on the road at any given time: how quickly levels rise, how long NO2 stays in the air, and how quickly levels fall.
All cities in focus (save Stockholm) went into lockdown mid-March, so March 2nd and March 30th highlight a consistent pre- vs. post-lockdown view. Explore your own custom timeframes using the date selectors below.
Visualizing the same data with an eye trained on net impact continues to support what we already know to be true and produces, for those more interested in succinct statement, an overall percentage decrease. The change for London is 15%, which is not an insignificant year-over-year reduction but appears modest compared to Copenhagen’s 47% and Paris’s 57%, and is a mere one-fifth of Madrid’s 65%.
Hover over the visualization below to reveal the daily year-over-year difference in average NO2 concentration.
It is obvious that this level of reduction in human activity is not reasonable or sustainable. At some point, with many of us hoping soon, things must return to normal. But isn’t there a degree to which we can carry these emissions reductions forward? What can we choose to change, on a manageable scale, about the way we live?
The concept of being better stewards of the environment is not a new one. We are well-versed in recommendations for improvement: conserve water, reduce waste, recycle, recycle, recycle. But it is easy to lose sight of how these small, voluntary changes are wise investments in a shared future.
Contending with COVID-19 has pushed the world into a pause which, under normal circumstances, would have been optimistic as a proposition, and impossible in execution. But we are here with the numbers in front of us, and the possible takeaways are many. In order to reduce the number of cars on the road at any given time, a well-maintained and reliable public transit system within a city is a must. Furthermore, the connection of cities in a national public transit network is something we can work towards and hope for. In restructuring the supply chain, we should aim to increasingly source food, commodities, and raw materials locally, thereby minimizing the need for long-distance shipping.
We would do well to educate ourselves about the history of our immediate communities, to become versed in our local politics. Write to, call, petition policymakers — make it a priority to vote. Infrastructural aims guided by shifts in policy are important, but the time between personal action and visible change might unfold over months, years, or decades. In light of the time it takes for these changes to take effect, persistence is key. These ends may start to feel distant, but each individual can take heart: there are small, no less impactful decisions for the day at hand, the effects of which are immediate and lasting.
Once a day, once a week, or even as sparingly as once a month, ask yourself: “Do I need to drive myself to get where I am going, or can I travel some other way?”
Our data-driven fashion face masks turn air quality visualizations into wearable stories, with printed patterns that reveal the real-world effects of COVID-19 lockdowns. Our goal is to provide a beautiful product that encourages you to keep yourself and those around you safe.
Please note: masks are non-medical grade and do not include N95 filters. These are for personal use only.
Data analysis, design and development by:
Douglas Sanchez, Rebecca Lantner, and Grace Park
Special thanks to Zona Kostic for leading an inspiring course,
Ning Chen for her input as TA, and last but definitely not least,
Jared Jessup for committing many hours to helping us debug
and encouraging us to work hard and think big.