Captured in April 2014, London's Canary Wharf, as seen from the Greenwich Observatory, is shrouded in a dusty smog. Typically, air pollution, caused by traffic and industrial activities, is a cause for concern in London. A 2019 report by the British Heart Foundation found that breathing the air in some areas of London is as harmful as smoking 150 cigarettes a year.
Pictured here almost exactly six years later, Canary Wharf's towering skyscrapers are clear to see and the smog is nowhere to be seen. As traffic has significantly fallen in the British capital during the coronavirus lockdown, so have pollution levels. Recent recordings from The Department of the Environment, Food and Rural Affairs show that NO2 (nitrogen dioxide – a common air pollutant) levels in London have decreased by more than a third and 165 air quality sites across the UK have recorded low levels of air pollution.
This image, created using data from the Copernicus Sentinel-5P satellite, represents the average NO2 (nitrogen dioxide) concentrations in the air in Europe between March and April of 2019. Although, Europe's average air pollution levels aren't as high as other places in the world, it's easy to see the impact of it in urbanised areas that are large transport hubs, like Milan, Madrid and Paris as well as parts of Germany.
Although weather differences between 2019 and 2020 may have had a minor effect, the data gathered between 13 April and 13 March 2020 shows a significant drop in NO2 levels across Europe. As many cities have been put under strict lockdown measures and transport via both air and land has been significantly reduced, the air quality has improved. According to the BBC, some UK cities have seen NO2 levels drop by as much as up to 60%.
Here, photographed in November 2017, the India Gate in New Delhi is barely visible as the city's air quality index (AQI) levels are usually a severe 200 – anything above 25 is deemed unsafe by the World Health Organization (WHO). Pollution in the Indian capital is sometimes so intense that AQI soars to 900, or even off the measurable scale entirely.
Since the country has been put under strict lockdown to battle the coronavirus pandemic, the skies have turned a rare, clear blue. Thanks to the many factories and construction sites closing as well as the lack of traffic on the streets, the AQI levels have fallen to below 20. One afternoon, after rainfall, levels dropped to seven – an unprecedented event in the Indian capital and the state of Delhi.
Before and after: places that have bounced back from the world's worst weather
Another Indian city battling with unbearable levels of pollution is Mumbai – home to around 19 million people according to the latest data and one of the most densely populated cities in the world. This image from 2017 clearly shows how polluted Mumbai's air can be. The city's annual average fine particular matter (an air pollutant) exceeded the World Health Organization (WHO) guidelines by more than five-fold in 2018.
This data captured by NASA clearly shows the impact lockdown measures have had on India's air quality. Aerosol optical depth (AOD) reflected in these images show the density of particles – dust, smoke and pollution – in the air. The bluer the colour, the more sunlight gets through these particles, the cleaner the air. A direct result of this decrease is on show in the Indian region of Jalandhar, Punjab where the Himalayan mountains more than 120 miles (193km) away can be seen for the first time in 30 years.
Kathmandu, the capital of Nepal sitting in the Kathmandu Valley, is one of the most polluted cities in the world. In 2018 the global Environmental Performance Index ranked Nepal as having the worst air quality out of 180 countries. The view of Kathmandu from the Buddhist temple of Swayambhunath usually disappears in a thick smog, as seen in this image.
Elsewhere in Asia, the Philippines consistently ranks among some of the most polluted countries in the world. A WHO study released in 2018 showed that the country had the third-highest number of deaths related to air pollution with about 45.3 deaths per 100,000 people. This image captured in 2017 shows the severity of air pollution in the capital Manila.
It's a rather different story in Manila now, photographed here on 5 April 2020. As the government imposed an enhanced community quarantine, the air quality has improved considerably. Data captured by the Environmental Pollution Studies Laboratory at the University of the Philippines Diliman revealed that there's been a 180% decrease in PM2.5 (larger particles in the air) since the start of the quarantine, which explains the clear blue skies Manila's locals are experiencing now.
Just a month and a half later, during the latter half of February, the changes are clearly visible. While over half a billion people were put on lockdown across the country to contain the coronavirus outbreak, it also meant that manufacturing, industrial activity and construction were halted and traffic was virtually non-existent. This translates into a 40% drop in NO2 levels in just a month which is equal to removing 192,000 cars from the roads.
With 34 out of the 46 most-polluted South American cities revealed in the 2018 World Air Quality Report located in Chile, this is the continent's most polluted country. The capital city of Santiago, home to six million people, has long battled air pollution caused by traffic, industrial activity, wood-burning stoves and even its geography – it's situated in a basin surrounded by mountains, meaning smog lingers, especially during the winter months.
Photographed here on 2 April 2020, Santiago's cityscape looks very different. Much like in other heavily polluted cities, Santiago's air has benefited from the lockdown. A report released by the University of Santiago's Antarctic Research Group revealed that the pollution levels in the city have dropped by as much as 30% in comparison to the same period in 2019.
A study conducted by World Bank in 2014 found that Colombia faces a real air pollution crisis in both urban and rural areas. Around one in 20 deaths in metropolitan areas were caused by air pollution and over 60% of the Colombian population were estimated to breathe air more polluted than the World Health Organization (WHO) guidelines deem safe. Sometimes the pollution is so bad, all traffic is banned for a day. Here, a thick, black smog is seen lingering over the Colombian capital in October 2015.
Thanks to a national quarantine, the number of cars on the streets has reduced dramatically, in turn almost completely changing the air in Bogotá and many other cities around the country. Photographed here on 2 April, Bogotá's smog has almost wholly cleared.
A similar fate has fallen upon Brazil's most polluted city São Paulo. Usually all of the city's main roads and motorways are packed with cars almost every hour of the day, contributing to dangerous levels of air pollution. A study last year found that the pollution levels in the city are not only harmful to people but also had a negative effect on tree growth.
An unusual blue sky is seen from Avenida Paulista in São Paulo on 31 March 2020. As the state-wide quarantine continues, most of the city's residents have stayed at home and traffic has decreased. According to a report by Swiss air technology company IQAir, it's one of nine major cities across the world that has seen the greatest increase in air quality since measures to halt the spread of coronavirus were introduced.
Air traffic is of course a significant air polluter and research conducted in 2019 revealed that the airline industry was on track to becoming the single biggest polluter within the next three decades. Pictured here are flights on a typical Monday in April 2019.
However, as country after country imposed various measures to contain and combat the spread of the coronavirus, data captured by Flightradar24 reveals the staggering drop in global air traffic. Both travel data provider OAG and Flightradar24 data analysed by the Guardian revealed global air traffic halved in March with an even more severe drop in April.
Another city that has benefited from the coronavirus lockdown is Los Angeles. Its traffic problems are notorious and Los Angeles is consistently ranked among the most congested cities in the US. This has inevitably led to serious problems with the air quality and left its downtown shrouded in a thick smog most of the time.
However, the stay-at-home order has meant a significant drop in LA's traffic, which has resulted in an astonishing drop in pollution. In fact, IQAir found it to have some of the cleanest air in any major city in the world on 7 April 2020. Captured here on 14 April, the snow-capped San Gabriel Mountains can be clearly seen from downtown LA.
Meanwhile, the USA's East Coast, mainly the northeast, has seen pollution levels plummet too. Here, a data visualisation map produced by NASA's Scientific Visualization Studio shows how concentrated NO2 (nitrogen dioxide) is in the air, especially in the region's major cities like Boston, New York City, Philadelphia and Washington DC.
As air and vehicle traffic has dropped significantly in these areas so has air pollution, clearly seen in this map. Researchers found a 30% decline in NO2 levels when comparing March 2019 and 2020. In New York researchers at Columbia University also found a 50% drop in carbon monoxide emissions due to the sharp decrease in traffic in the city and state.
Images released by NASA in February, when the Chinese city of Wuhan was under a strict lockdown, captured a significant reduction in light pollution too. As businesses and transport links were shut down, this close-up of the Jianghan District, a commercial area of Wuhan, reveals the impact the lockdown has had on light pollution and scientists expect to see a similar picture painted across Europe too. Reduction in light pollution is beneficial as it has a huge impact on healthy sleeping patterns in both humans and animals, especially in urban areas.
Lockdown measures have also contributed to a drop in noise pollution, especially significant to animals living in urban areas, like this raccoon enjoying the peace of New York City's Central Park. Deutsche Welle reported that a variety of urban animals, most notably birds, are benefiting from the lack of ambient noise caused by planes, cars, public transport and people. Similarly, Forbes has reported on a reduction of noise in the oceans from ships, which is directly linked to stress levels in sea creatures, and seismologists have recorded less seismic noise in the Earth's crust too caused by human movement. Now discover more images that show the true impact of climate change.