You can see why Hitler was an environmentalist.
Political disturbance and armed conflict in the Middle East since 2010 have had the unintended consequence of making the air cleaner.
Researchers say that in countries like Syria and Iraq, levels of air pollutants have fallen dramatically.
The amount of nitrogen dioxide in the air over Damascus has fallen by up to 50% since start of the civil war.
The authors believe their work has important lessons for projections of global emissions.
So we start a bunch of civil wars in America and Europe to lower the level of nitrogen dioxide,
In countries like Syria, where millions of people have attempted to flee the fighting since 2011, levels of nitrogen dioxide plummeted over Damascus and Aleppo.
But in nearby Lebanon, there was a "drastic" rise of up to 30% of the same pollutant, thanks to the influx of refugees. The scientists say that this was very unusual as economic growth in Lebanon declined significantly at the same time.
"It's quite remarkable," lead author Dr Jos Lelieveld from the Max Planck Institute for Chemistry told BBC News.
It's an environmentalist's dream come true.
But in Iraq, the rise of so-called Islamic State can also be clearly seen in the air quality data.
"In Karbala, to the south of Baghdad, a mostly Shiite area, the increase in pollutants continues," said Dr Lelieveld.
"But if you look to the area northwest of Baghdad, where Islamic State is in charge, there you see that things are going in another direction."
Who knew ISIS were environmentalists?