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Paper short abstract:

Artificial light at night (ALAN) has recently been reframed as an environmental pollutant. To assess the problem, physicists are developing new methods and models to measure light emissions. Yet, atmospheric phenomena make it a difficult task so that scientists rely on citizens for better data.

Paper long abstract:

Artificial light at night is not only a growing research field, but also an increasing environmental problem and public concern. Scientists find evidence that light at the wrong time that is, at night, disrupts sleep rhythms and hormonal processes with negative effects on ecosystems and human health. However, quantifying the problem is all but simple. Light waves are not just emitted by anthropogenic sources, but propagates into and interferes with particles in the atmosphere: Clouds reflect it adding to sky glow and rendering remote sensing of light emissions more difficult. Blue-rich light scatters more in the atmosphere than shorter wavelengths, leading dark-sky activists to oppose energy-efficient LED lighting.

In my talk I take these atmospheric challenges of light pollution mitigation as a starting point to reconsider our recent citizen science campaign ‘Nightlights’ (Sept.-Nov. 2021). The project was explicitly designed to bridge the cloudy and scattering gap between the sources of light emissions on the ground and their documentation by satellites in space. So far, we have counted over 250.000 lights in public spaces, mainly in Germany. Currently, a transdisciplinary team correlates the citizen science data with satellite data to better understand the actual sources of light emissions in different places. Yet, the atmospheric poses epistemic challenges. While remote sensing experts need to cope with the variability of satellite data, the highly engaged citizen scientists need to accept that ‘the atmospheric’ stands in their political way as it hampers the production of place-based scientific evidence for anthropogenic light pollution.