Whether natural or caused by human activity, clouds contribute to warm or cool Earth: either they reflect incoming sunlight, or trap heat from the surface in the atmosphere. Similarly, scientists were uncertain how contrails contributed to each of these effects.

The no-flight times that occurred due to the covid-19 is an unparalleled empirical setting, because it makes possible to compare time-based scenarios: through the lens of satellites we now can explore the atmosphere with and without the effects of more than 90,000 daily flights. 

We take now the opportunity to study and test the relationship between the presence of aerosol in the atmosphere, which is considered cause of global warming, and contrails generate by planes using satellite data from ESA Sentinel 3 Satellite S3A_OL_1_EFR Band 15 and  QGIS 3.12.3visualisations.

While we assume that contrails are only partially responsible for aerosol emissions, we look at the presence of aerosol at flight altitude over Northern Italy since the lock-down inception and benchmark it with previous years.

Our analysis shows that cruise-altitude aerosol range has halved over the area of research during the pandemic when compared with the same period in previous years (2016-2019). The timeframe considered is between 22nd March and 3rd May, which in 2020 represent total lockdown period in Italy. As we are aware that at this early stage research, cloud formations in our image collection may skew the data, we observe that the aerosol depth range recorded in the past years is constantly in the 0.24-0.36 units and above, while a recent observation shows a widespread aerosol thickness in the range of 0.12-0.24 units, over a full spectrum available to the Sentinel 3 product of 0.-0.6 units.

We believe that future research aimed at comparing the change in temperatureof that region in the same period, will provide novel insights about the relation between contrails and the temperatures at ground level. Scenario predictions of the impact of air passengers gradually returning to fly could be also designed and analysed.

Moreover, this study can be a baseline for the aviation industry that changes the metrics of their environmental impact and it could be replicated and expanded across industries and geographies.

After our observations, we can conclude that the Planet is taking a breath of fresh air with the hope that a and it will be the case in the future for a more in-depth measurement of land temperature along with aerosol.

Clarifying the impacts of contrails on the environment will help society to better address and better understand the causes of climate change, will help airlines to improve efficiency and sustainability and to create people awareness on this important issue.