Emissions of the greenhouse gas nitrogen dioxide have been slashed by a FIFTH since February due to the coronavirus pandemic, NASA finds
- NASA analysed nitrogen dioxide emissions at 5,756 sites in 46 countries
- Compared 2020 figure with the multi-year average for previous years
- Revealed an average drop of 20 per cent from February around the world
- In cities, it ranged from a 20 to 60 per cent reduction in NO2 emissions
The coronavirus lockdown has led to a 20 per cent global reduction in the amount of nitrogen dioxide being spewed into the atmosphere since February.
NASA analysis looked at how much of the greenhouse gas has been produced at 5,756 sites in 46 countries.
Nitrogen dioxide (NO2) is less prevalent than carbon dioxide, but is 300 times more potent as a contributor to global warming.
Nitrogen dioxide is an air pollutant that is primarily produced by the combustion of fossil fuels, with major emitters being vehicles and industry.
The drop in concentration was larger in cities, with NO2 drops of between 20 and 60 per cent seen in 50 of the 61 metropolises that were analysed.
Pictured, six maps from NASA focusing on Wuhan reveal the concentration of nitrogen dioxide over three periods including before Lunar New Year, during celebrations and after the festivities in 2019 and 2020
‘We all knew the lockdowns were going to have an impact on air quality,’ said lead author Christoph Keller at NASA’s Goddard Space Flight Center in Maryland.
‘It was also soon clear that it was going to be difficult to quantify how much of that change is related to the lockdown measures, versus general seasonality or variability in pollution.’
NASA compared the average data on the ground from 2020 to the multi-year average, accounting for natural variation in weather and atmospheric circulation.
The researchers took all the pre-existing data and modelled what 2020’s emissions would have looked like had the coronavirus pandemic not occurred.
This was then compared to the actual measurements.
‘In some ways I was surprised by how much it dropped,’ said Dr 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.’
NASA captured the lighting changes in Jianghan District, a commercial part of Wuhan, after authorities suspended travel and placed restrictions on other activities, such as social gatherings. The two images were taken 16 nights apart
Wuhan, the Chinese city which is home to more people than London (11million) was the initial site of the outbreak of SARS-CoV-2.
As a result, it was the first place to show a marked decrease in air pollution, around February time, recording a 60 per cent lower number than predicted.
This is due to the strict lockdown rapidly implemented, which made any form of travel out of the city forbidden.
A 60 per cent decrease in Milan and a 45 per cent decrease in New York followed shortly afterwards, as their local restrictions went into effect following their emergence as a viral epicentre.
‘You could, at times, even see the decrease in nitrogen dioxide before the official policies went into place,’ said co-author Emma Knowland with NASA’s Universities Space Research Association (USRA).
‘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.’
NO2 emissions increase by a THIRD over the past 40 years
Widespread use of nitrogen-based fertiliser is jeopardising ambitious climate targets and putting the world at risk of overshooting the Paris Agreement.
Common synthetic fertilisers, used by farmers to increase crop growth, produce huge amounts of nitrous oxide (N2O), a greenhouse gas.
It is less prevalent than carbon dioxide, but is 300 times more potent as a contributor to global warming.
The dangerous gas depletes the ozone layer, which protects us from the harmful ultraviolet rays of the sun, and remains in the atmosphere for a century.
A landmark study has found human-induced emissions of the chemical have surged since the 1980s, increasing by 30 per cent over the past four decades.
Annually, humans now create 7.3 trillion grams (Tg) of nitrogen a year and more than half (3.8 trillion grams [3.8Tg]) comes directly from agriculture.
This figure is increasing every year at a rate of around 1.4 per cent, according to the data.
The researchers warn that if N2O continues being spewed out at its current rate, global temperatures will soar to 3°C above pre-industrial levels by 2100.
The Paris Agreement is a landmark set of environmental targets signed by almost all nations in 2015, which aims to limit warming by the end of the century to less than 2°C, but hopes to hit its more ambitious target of 1.5°C.