NASA’ s study of worldwide air pollution trends over the last decade has highlighted humanity’s impact on global air quality.
Using high-resolution satellite maps gathered from the Aura satellite, the NASA team analysed nitrogen dioxide levels around the globe between 2005 and 2014. They found that where governments had stepped in with deliberate policies to curb emissions their influence on nitrogen dioxide levels in the atmosphere could clearly be seen.
“These changes in air quality patterns aren’t random,” said lead researcher, Bryan Duncan. “When governments step in and say we’re going to build something here or we’re going to regulate this pollutant, you see the impact in the data.”
NASA identified the United States and Europe as the largest emitters of nitrogen dioxide, but both regions also showed the most dramatic reductions between 2005 and 2014, with both territories reducing emissions by as much as 50%.
On the other hand, China, the world’s growing manufacturing hub, saw an increase of 20 to 50% in nitrogen dioxide emissions. However, demand for cleaner air from Beijing’s middle-class residents has caused a reduction in emissions in the city.
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, but levels have increased in neighbouring countries as Syrians seek refuge.
“By monitoring levels of nitrogen dioxide from space we can see and quantify the effects of things like energy usage, environmental policy and even civil unrest on air quality across the globe,” said Duncan.
The space-based mapping allowed scientists to gather information on pollution for cities and countries that have limited ground-based air monitoring stations.
South Africa, for instance, was shown to have the highest nitrogen dioxide levels in the Southern Hemisphere, but has achieved decreases in Johannesburg and Pretoria after new cars were required to have better emissions controls. The heavily industrialized area just east of the cities, however, shows both decreases and increases. The decreases may be associated with fewer emissions from eight large power plants east of the cities since the decrease occurs over their locations.
“We had seen seemingly contradictory trends over this area of industrial South Africa in previous studies,” said co-author, Anne Thompson. “Until we had this new space view, it was a mystery.”