How Would a COVID-Free 2020 Compare for Pollution?

2020 has been a miserable year for people all across the globe, but the environmental implications of coronavirus have, on occasion, provided a small silver lining. With many industries all but shutting down and far fewer vehicles on our roads all over the world, emissions of certain contaminants fell significantly.

For the first time, NASA has attempted to quantify just how big a difference COVID-19 made to air pollution last year. By using sophisticated computer modelling software and mapping those projections against real-life monitoring data, the space agency was able to arrive at an exact figure for the drop-off in emissions of nitrogen dioxide (NO2).

Difficult calculations

In order to assess the size of the impact of the pandemic on our emissions, the NASA team had their work cut out for them. Natural fluctuations in weather patterns and in atmospheric circulation mean that no two years are exactly the same in terms of NO2 emissions. Therefore, determining the extent of COVID-19’s effect would not be as simple as comparing and contrasting with 2019 or other previous years.

Instead, the NASA scientists relied upon the same modelling programmes which they use to project emissions totals every year. These already take into account the natural variations mentioned above, so it was simply a case of cross-referencing the software’s estimations against emissions data collected by advanced monitoring techniques employed by data centres on the ground.

Significant differences

In total, the scientists were able to check their projections against data collected at 5,756 monitoring centres in 46 nations around the world. Speaking in terms of urban epicentres, 50 of the 61 cities involved in the study showed reductions in NO2 emissions by between 20% and 50%. That’s a significant drop-off from what had been expected to happen with no behavioural changes.

“In some ways I was surprised by how much it dropped,” explained Christoph Keller “Many countries have already done a very good job in lowering their nitrogen dioxide concentrations over the last decades due to clean air regulations, but what our results clearly show is that there is still a significant human behaviour-driven contribution.”  

Ahead of the curve

The first reductions were noted in Wuhan City in China, which is the location where the pandemic first began. The Lunar New Year means that emissions levels often fall in China at that time of year, but unlike every other celebration, 2020’s festivities weren’t followed by a rebound in NO2 levels. Instead, they were 60% lower than expected, while similar reductions of 60% and 45% were soon observed in Milan and New York, respectively.

“You could, at times, even see the decrease in nitrogen dioxide before the official policies went into place,” commented paper co-author Emma Knowland. “People were probably reducing their transit because the talk of the COVID-19 threat was already happening before we were actually told to shut down.” In any case, the study provides firm evidence of what can be achieved if the human race takes swift, decisive and far-reaching action to curb their emissions going forwards.