There's been talk for a while now that climate change could bring with it droughts, economic collapse, and maybe armed conflict. One recent study claimed that climate change might have even precipitated the Syrian civil war. But, according to a new report in Science Advances, it seems this cause and effect relationships works the other way too: Social and economic upheaval appears to cut air pollution.
"You're quite aware the Middle East is a region that catches a lot of attention with political problems and upheaval and armed conflict," Jos Lelieveld, lead author of the new study and a professor at the Max Planck Institute for Chemistry in Mainz, Germany, told reporters during a Thursday morning press conference. "But although atmospheric and environmental changes in the Middle East have not particularly been in the center of attention, they're actually also quite remarkable, and we now find that there are clear links between these two."
Economic sanctions in Iran led to reduced air pollution, likely because those sanctions reduced the number of oil tankers traveling through the Persian Gulf.
Since 2005, Lelieveld and his colleagues have used instruments onboard a NASA satellite to track levels of nitrogen dioxide, which helps produce ozone in the atmosphere and disperses energy from the sun, throughout the Middle East. From 2005 to 2010, Lelieveld said, "the Middle East has been one of the regions with the fastest-growing air pollution emissions." In Riyadh, Saudi Arabia, for example, nitrogen dioxide levels increased nearly 25 percent, and they increased by more than half in Tehran, Iran, by 2011—increases likely brought on by growing shipping and transportation in rapidly expanding economies.
But around 2010, that trend began to level off, or sometimes even reverse. By 2014, Riyadh was almost back to 2005 nitrogen oxide levels, and there were similar reversals in Cairo, Tehran, and several other cities in the region.
What happened? By examining a variety of economic and political factors, Lelieveld said, the team pieced together rough explanations for the patterns they found. For example, clean-air regulations in Greece appear to have led nitrogen dioxide emissions to grow slowly until 2008, but emissions dropped sharply afterward, corresponding to the beginning of the country's financial and economic crisis. Similarly, economic sanctions in Iran led to reduced air pollution, likely because those sanctions reduced the number of oil tankers traveling through the Persian Gulf.
Political unrest also played a significant role, the researchers argue. The civil war in Syria, for instance, forced millions to flee to nearby countries and, in turn, led to sharp nitrogen dioxide declines in one of the largest cities, Aleppo. Something similar happened in Iraq, Lelieveld and his team say, where Islamic State occupations in Tikrit and Samarra have indirectly cut air pollution.
"It is tragic that some of the observed [nitrogen dioxide] trends are associated with humanitarian catastrophes," the researchers write, though Lelieveld posited that the data will at least help researchers improve climate models and aid policymakers grappling with how to mitigate climate change.
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