Air quality laws and regulations appear to have helped reduce NO2 levels in Western Europe and the USA over the last decade
A world map showing air pollution trends over the last decade has been produced to display the human footprint on air quality.
The map, produced by NASA, shows changes in nitrogen dioxide concentrations â€“ a common emission from cars, power plants and industrial activity â€“ over the past decade.
It suggests that more recent air quality laws and regulations have had a considerable impact on NO2 in the USA and Europe.
A NASA science team led by Bryan Duncan, an atmospheric scientist at the Goddard space flight centre, made observations made from 2005 to 2014 across various regions and 195 cities worldwide using the ozone monitoring instrument on NASAâ€™s Aura satellite.
Two types of data are visible on the map, with blue and green colours indicating where the concentration of tropospheric nitrogen dioxide has fallen, and orange and red demonstrating areas where levels have increased.
According to NASA, previous studies using satellites at lower resolutions missed air quality variations over short distances, but this new space-based view â€œoffers consistent information on pollution for cities or countries that may have limited ground-based air monitoring stationâ€ and tells a â€œunique storyâ€ for each region.
To look for explanation of trends in nitrogen dioxide levels, the researchers compared the satellite record to information about emission control regulations, national gross domestic product (GDP) and urban growth.
Mr Duncan said: â€œWith the new high-resolution data, we are now able to zoom down to study pollution changes within cities, including from some individual sources, like large power plants.â€
Findings showed that the United States and Europe are among the largest emitters of nitrogen dioxide.
However, both regions also showed the most dramatic reductions during the ten years. Nitrogen dioxide has decreased from 20% to 50% in the United States and as much as 50% in Western Europe.
Researchers concluded that the reductions are largely due to the effects of environmental regulations that require technological improvements to reduce pollution emissions from cars and power plants.
Meanwhile China saw an increase of 20%-50%, which is attributed to increased manufacturing and the South African region had the highest nitrogen dioxide levels in the southern hemisphere, although the map shows a complex situation playing out between cities and neighbouring industrial areas.
In the Middle East, increased nitrogen dioxide levels since 2005 in Iraq, Kuwait and Iran likely correspond to economic growth in those countries. However, in Syria, nitrogen dioxide levels decreased since 2011, most likely because of the civil war, which has interrupted economic activity and displaced millions of people.