Nitrogen dioxide concentrations over China – January 1 to February 25 2020. Data courtesy of NASA and ESA/Copernicus. Images from NASA Earth Observatory by Joshua Stevens, using modified Copernicus Sentinel 5P data processed by ESA.
The world is in the grip of a global pandemic with many countries in a one form of lockdown or another – the UK had its most restrictive measures instigated on Monday – and most businesses are doing their best to just keep going. However, there are signs of hope. The planet is benefiting from the reduction in human productivity and this can be seen from space.
Data collected by ESA’s Sentinel-5P satellite is showing a reduction in air pollution – specifically the nitrogen dioxide concentrations – over both China and Italy.
In China, the 10 ten-day moving average from mid-December to end February reduced significantly – up to 40% over some cities – as the country restricted daily life to fight the virus, and as the country has begun to come out of its lockdown in early March the levels have begun to rise again. The Copernicus Atmosphere Monitoring Service (CAMS) used the data to calculate that China saw a 20-30% reduction in surface particulate matter over the same period.
Equally, Italy has shown a similar decline in nitrogen dioxide concentrations as it followed similar restrictions. Using a similar moving average to China from the start of January to mid-March there is a noticeable reduction, particularly noticeable over Northern Italy which was the initial epicentre of the Italian outbreak. ESA have produced a visualisation showing this reduction during 2020, which can be accessed here.
It’s likely that this improved air quality is due to the reduction in pollution from industry, transport and other activities. Although, it should be noted that China for example always has a drop in air pollution at this time each year due to the Lunar New Year celebrations – although the normal rebound after this event has not been observed.
Of course, as more countries place similar limitations on work and movement then we’d expect to see similar improvements in air quality to continue. Even in the UK the London Air Quality Network, run by King’s College, has shown similar drops in both nitrogen dioxide concentrations compared to average, although at the moment this is being linked to a reduction in traffic.
This data is collected by the Earth Observation satellite Sentinel-5P, also known as the Sentinel-5 Precursor, which carries a single instrument, the TROPOspheric Monitoring Instrument (TROPOMI). TROPOMI combines four imaging spectrometers, each split into two bands resulting in two bands in the ultra-violet spectrum, two in the visible spectrum, two in near infra-red and the last two in shortwave infra-red. It has a spatial resolution of seven square kilometres and swath of 2,600 km. It can map a range of trace gases and pollutants in the atmosphere including nitrogen dioxide, ozone, formaldehyde, sulphur dioxide, methane, carbon monoxide and aerosols.
NASA have been collecting similar measurements from their Ozone Monitoring Instrument (OMI) on their Aura satellite, as can be seen in the image at the top of the blog.
Other signs of hope observed around the world have included:
- The canals of Venice have become still without gondolas, making the water very clear and tiny shoals of fish can be seen through the water reportedly enabling diving birds to return to feeding on the canals.
- Dolphins have been seen swimming in the port of Cagliari on the Italian island of Sardinia.
In addition, the epicentre of the pandemic, the Chinese city of Wuhan, has had its travel restrictions eased from today and the lockdown is planned to be eased from April 8th. This is not a full return to daily life, which was curtailed just over three months ago on the 23rd January, it is a start. There are still many questions to answer and understand, as to whether the outbreak in China has been slowed, stemmed or even stopped. However, it is a welcome beacon of hope for the world.
