Europe’s night sky is getting bluer and bluer

The nocturnal environment of much of the world has changed significantly with the introduction of artificial lighting. Although data on the spatial and temporal variation in the intensity of artificial lighting are available at regional and global scales, data on the variation in their spectral composition have been collected in only a few locations, making it impossible to map the variation in associated environmental and hazard risks the human health.

Researchers from Complutense University of Madrid (UCM) in Spain and the University of Exeter in the UK have used digital camera images of astronauts on the International Space Station and America’s Suomi NPP satellite to pinpoint the true growth in light pollution verify Europe. For the first time, the data from both satellites have been combined to be able to give realistic information about the increase in light pollution in a large area (until now, the use of images from the space station has been limited to small areas, such as cities).

This allowed them to map the variation in spectral composition of illumination across Europe for the years 2012-2013 and 2014-2020. These images show a widespread spectral shift at a regional scale, from that associated primarily with high-pressure sodium lighting to that associated with broader white and more blue-emitting light-emitting diodes (LEDs), a trend that greatly increases the risk of harmful effects on ecosystems. That’s because blue light is an essential part of sunlight and therefore better tricking the brain into thinking it’s daytime, altering the circadian cycle more and all that entails. Other colors, like red, are not “everyday” and do not cause this sharp change in the circadian cycle.

The growth between 2012-2013 and 2014-2020 in the green color is of the order of 11.1%. In blue it is 24.4% for the same period. This confirms the pessimistic estimates that the same researchers published last year based on the forecast of sales of LED lamps.

Europe at night, in a photo taken from space in 2016. (Image: NASA Earth Observatory / Joshua Stevens / Suomi NPP VIIRS / Miguel Román / NASA’s Goddard Space Flight Center)

The changes are happening very unevenly in Europe.

In Spain, the proportion of blue light emitted increases by 13% compared to green light. This can affect people’s health by deteriorating sleep quality. It also poses a threat to ecosystems in general. The study specifically looks at the impact on moths (which are important pollinators) and bats.

The team’s latest study in this research area is entitled ‘Environmental risks from artificial night lighting widespread and increasing across Europe’. And it was published in the journal Science Advance.

Researchers from the Complutense University of Madrid’s GUAIX group, Alejandro Sánchez de Miguel and Jaime Zamorano, lead one of the leading groups in the field of light pollution study and have conducted pioneering studies in the field worldwide. They are currently advising the rotating Presidency of the Council of the European Union through the UNA4CAREER programme, the funding of which allows the continuation of this project to map Europe at night. (Source: UCM)

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