We've shared posts with startling changes in air pollution that let us see more of our natural surroundings. The Himalayas have been revealed from hundreds of kilometres away, satellite visibility has never been higher, and seismologists have likened the drop in Earth's vibrations to Christmas Day.
Lower pollutants are an expected side-effect of the COVID-19 pandemic that has shown the general public that we can survive with far fewer atmospheric pollutants while much of our traffic and industry has been put on hold.
Within our own borders, we've often wondered how pollution levels have dropped. Thanks to the Land and Atmosphere Remote Sensing group at the Physical Technology Center/Polytechnic University of Valencia we now have hard data. The team of researchers - Elena Sanchez Garcia, Itziar Irakulis Loitxate and Luis Guanter - have collected data from the European Space Agency's Sentinel-5P satellite mission.
As you'd expect, there are huge drops in pollution over many major cities but most surprising is where air pollutants have gone up. The images below measure the amounts of nitrogen dioxide above some of our most dense metropolitan areas as nitrogen dioxide is a substrate of combustion which includes vehicle engines and coal-burning power plants.
Sydney and Brisbane show very obvious decreases in nitrogen dioxide emissions as the density of traffic has decreased from around 144 micromoles per square meter (red) to just over 80 and 65 to the higher 40s respectively. Sydney, by design or lack thereof, is more of an open sprawl that has daily pollution entering into the city from the suburbs and less of a focal point than Brisbane which serves as a hub for traffic. Both have shown a relative decline in nitrogen dioxide emissions.
An eyebrow-raising find was that Melbourne and Newcastle had increased their nitrogen dioxide emission concentration. Newcastle, known for its coal-heavy industry increased emission concentration by 20% overall while Melbourne's exploded by 40%. We are unsure specifically why these cities have shown large increases at this time, especially as Melbourne attributes 75% of its emissions to vehicles and is majorly dependent on vehicular travel while many are not commuting to work.
Other considerations include the added usage of power by those isolating at home which means greater dependence on coal power and fire reduction burns have begun in the surrounding suburbs.
A further consideration is that winds affect the presence of air pollution, and the current atmospheric trends around our cities could be either allowing nitrogen dioxide build-up or dispersing it.
Overall, Perth has shown no significant change.
The research required in understanding the many factors of nitrogen dioxide concentration is challenging due to the many variables involved including atmosphere conditions such as wind and rain, time of day/week/month and population density and behavioural patterns all must be considered. Recent stubborn bushfire particles could also confound data and make the findings unclear.
While Sydney and Brisbane show promise for a brighter future with fewer emissions, we must also understand why and how other major metropolitan areas are increasing so that we might curb these behaviours and use this unique time for the betterment of all mankind.