It's released from the tailpipes of cars, and the smokestacks

of power plants. Together, these emissions affect the quality

of the air we breathe. Since 2004, an instrument aboard NASA's AURA

satellite has measured levels of nitrogen dioxide in Earth's atmosphere.

In 2014, we released satellite images that show how

environmental regulations have led to reductions in nitrogen dioxide

over major U.S. cities. Now, we've created a global maps

that allow us see how levels have changed around the world over the last decade.

In Western Europe, despite the recent vehicle emissions scandal

nitrogen dioxide levels have decreased by as much as 50 percent

due to tighter environmental controls. In China, we see an increase

in levels over most of the country due to a rise in coal use for power generation

but decreases for some cities, like Beijing, where a growing

middle class is now demanding cleaner air. In the Middle East, we see

decreases in nitrogen dioxide levels over Syria due to the country's

civil war and displacement of its population. Meanwhile, levels have

gone up in neighboring countries where millions of Syrians have taken refuge.

In the U.S., the only increases are in regions with intensive

oil and natural gas extraction, including fracking. In North Dakota

and Texas, we see increases of 30% in some areas.

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.