[Reading Science] "The Idea That COVID-19 Lockdowns Restored Blue Skies Is a Misconception"

Analysis of NASA Satellite Images Shows Ultrafine Dust Concentration Unchanged
Significant Decrease Confirmed Only in Northern China During Lockdown Period

Changes in PM 2.5 concentrations in China observed via satellite in February 2019 and February 2020. Photo by NASA

[Asia Economy Reporter Kim Bong-su] Due to the COVID-19 pandemic, factories emitting air pollutants around the world stopped, and transportation such as aviation was also halted. Many people believed that the air had become cleaner, but research results showed that this was not actually the case.

According to NASA on the 24th (local time), nitrogen dioxide (NO2) emissions from trucks, passenger cars, and other transportation means sharply decreased in the early stages of the pandemic last year. The reduction of nitrogen dioxide was confirmed not only in space but also on the ground. Social media and news were flooded with photos of blue skies where thick smog had disappeared, and people thought that air pollution had significantly decreased overall due to COVID-19.

However, a decrease in nitrogen dioxide does not necessarily lead to a decrease in PM 2.5. According to NASA, nitrogen dioxide emitted into the atmosphere can interact with other chemicals to form PM 2.5, but this is not always the case. In fact, a research team led by Professor Melanie Hammer from Washington University in St. Louis analyzed the distribution of fine particulate matter (PM 2.5) on Earth using satellite images taken by NASA and found that overall, there was not much difference in concentration before and after the pandemic.

Based on satellite image data taken by NASA, the research team created new computer models to map PM 2.5 concentrations in North America, China, and Europe during the early pandemic period. The results showed that PM 2.5 concentrations in the atmosphere of these regions fluctuated due to seasonal factors as in recent years, but no effects from pandemic-related lockdowns were found. The team mapped monthly PM 2.5 concentrations from January to April for the years 2018, 2019, and 2020 for comparison. In North America and Europe, PM 2.5 concentrations from January to April 2020, during the lockdown period, showed no significant difference from previous years. However, in China, a significant decrease was confirmed in northern areas such as Beijing, where strict lockdowns were concentrated.

The research team analyzed these results by noting that in Europe and North America, average PM 2.5 concentrations in the atmosphere had been steadily decreasing, so the lockdown measures due to the pandemic did not have a major impact. On the other hand, in northern China, known as the "world's factory" due to its dense manufacturing, PM 2.5 concentrations were usually very high, so the lockdown measures had a relatively greater effect.

This content was produced with the assistance of AI translation services.