Evaluation shows

Clean sky during Covid lockdown

10. August 2022, 10:00 Uhr | Tobias Schlichtmeier
Forschungsflieger HALO
Launched into near-empty airspace during the May 2020 Covid lockdown: the »HALO« research aircraft studied the impact of limited mobility on air quality.

The lockdowns during the pandemic reduced fossil fuel burning by about one-third in the early 2020s. These provided atmospheric research with a unique opportunity to quantify air pollution over a wide range. The findings are groundbreaking.

During the first lockdown of the Covid pandemic, soot concentrations in the atmosphere over western and southern Europe almost halved. This is shown by the comparison of two measurement campaigns of the German research aircraft »HALO« from 2017 and 2020.

About 40 percent of the reduction was due to reduced anthropogenic emissions, according to a new study. The results reflect the strong impact of human activities on air quality and the importance of soot as a major air pollutant and climate driver in the Anthropocene, write researchers from the Max Planck Institute for Chemistry, the University of Bremen, Johannes Gutenberg University Mainz, the German Aerospace Center (DLR), the University of Leipzig and the Leibniz Institute for Tropospheric Research (TROPOS) in the journal Atmospheric Chemistry and Physics (ACP).

During the Covid lockdowns in early 2020, the research team flew over Germany, the Benelux countries, Great Britain, France, Spain, Italy, – in other words, large parts of Central, Western and Southern Europe. It determined the mass of soot and the particle concentrations in the lower troposphere using the HALO (High Altitude and LOng range) research aircraft in both the planar and vertical profiles as part of the »BLUESKY« campaign. The team then compared the results with measurements taken in July 2017, when the researchers had studied the area under »normal«, or pre-Covid conditions as part of the »EMeRGe« EU campaign.

The comparison shows a significant pandemic-related improvement in air quality: on average, the amount of soot in the lower troposphere in southern and western Europe fell by 41 percent. This enormous figure was verified using traffic data and information on gasoline consumption during the lockdown periods. The researchers attribute the decrease to two main reasons: efforts already underway to reduce soot emissions in Germany and Europe (three to nine percent), and reduced mobility due to the pandemic lockdowns, which accounted for 32 to 38 percent. The comparative data was also incorporated into an Earth system model to determine what effect fewer soot emissions in Europe would have on the climate in the long term.

Soot is harmful to health and contributes to global warming

The background is that soot near the ground is not only a particularly harmful part of particulate matter. Up in the atmosphere, the tiny particles contribute to global warming because their dark surface heats them up and they release heat into the environment. Unlike long-lived greenhouse gases such as carbon dioxide, however, soot is short-lived and remains in the atmosphere for only a few days to weeks.

»Reduced soot emissions through less burning of fossil fuels such as diesel, coal, oil or even wood would quickly help the health of millions of people. In addition, our measurements and model calculations show that less soot in the atmosphere makes an important contribution to mitigating climate change,« explains Mira Pöhlker from TROPOS in Leipzig. The atmospheric scientist, who also conducts research at the Max Planck Institute for Chemistry in Mainz, hopes that some of the behavioral changes of the Covid era, such as more video conferencing and home offices, and thus fewer flights and trips to work, will be maintained.

Pöhlker and the team are currently working on a new study and are also bringing psychologists on board. They want to find out whether offers like the nine-euro ticket can actually lead to a sustainable change in people's mobility behavior. »In addition to a general reduction in traffic, it is important to create incentives for low-emission mobility. In my opinion, heavily subsidized public transport is an important stimulus.«

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