The surprising byproduct of conflict in the Middle East? Cleaner air

After increasing steadily for years, air pollution in the Middle East dropped off dramatically around 2010, and it has been plummeting ever since.

Unfortunately, the cleaner air is not, by and large, a result of pollution-control measures. Rather, it's an effect of the unrest, political upheaval, and armed conflict in the region.

That's according to a paper published Friday in the journal Science, the first to propose a correlation between the political climate and the atmosphere in the Middle East.

Specifically, the study examined levels of nitrogen dioxide, a byproduct of burning fossil fuels and a chemical that plays a role in the formation of ground-level ozone. It found that, between 2005 and 2010, the Middle East had the world's fastest growing air pollution emissions, in line with its economic growth.

But that trend was interrupted in 2010. Air pollutants declined steeply around the same time as regional unrest rocked the region, stalling economic activity.

“It is tragic that some of the observed recent negative NO₂ trends are associated with humanitarian catastrophes,” the paper concluded.

The study used tools aboard NASA's Aura satellite, including the Ozone Monitoring Instrument, to monitor atmospheric pollutants in the Middle East. The results were startling: Regions of cleaner air could be detected from space, and, in the Middle East at least, were an accurate indicator of crises on the ground.

“It is amazing how strong the changes have been in the Middle East,” Jos Lelieveld, the lead author of the study and a researcher at the Max Planck Institute for Chemistry in Mainz, Germany, told Nature Middle East. "Each of these countries has an individual story."

In Iran, international sanctions precipitated an economic downturn that coincided with plummeting levels of pollutants after 2010. In Iraq, levels of nitrogen dioxide began dropping sharply around the cities of Baghdad, Samarra, and Tikrit in 2013, when the Islamic State began attacking or occupying those Iraqi cities, devastating the regional economy.

In Egypt, public turmoil has been associated with dropping levels of air pollution since 2011.

Similarly, the Syrian civil war appears to have drastically cut air pollution over cities where Syrians have fled, like Aleppo and Damascus, where nitrogen dioxide has fallen by up to 50 percent since the start of the conflict. Meanwhile, the cities Syrians have gone to seek refuge – like Beirut and Tripoli, in Lebanon, have seen increases in nitrogen dioxide levels.

How might scientists and world leaders use this new research?

Monitoring levels of nitrogen oxide emissions from space can be used as a "thermometer" of crises on Earth, perhaps offering insight into broader patterns of conflict and unrest Dr. Lelieveld told the New York Times, .

The space-based observations may also offer insight into the wellbeing of regions in which outside access or freedom of press is limited.

The data may even serve as a new way to measure the effectiveness of sanctions, as dropping nitrogen dioxide levels signal economic slowdown.

Finally, it may also offer lessons for global projections of emissions and mapping of climate change scenarios.

But, as Lelieveld told the Times, war is a human – and ecological – catastrophe, and dropping levels of pollutants in the Middle East should not be taken as a positive sign.

“This is not the ‘silver lining of war,'" he said. “It’s just an indicator of what’s going on.”