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diff --git a/environment.bib b/environment.bib
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+++ b/environment.bib
@@ -85,3 +85,17 @@
   eprint   = {https://www.science.org/doi/pdf/10.1126/science.abq7781},
   abstract = {The artificial glow of the night sky is a form of light pollution; its global change over time is not well known. Developments in lighting technology complicate any measurement because of changes in lighting practice and emission spectra. We investigated the change in global sky brightness from 2011 to 2022 using 51,351 citizen scientist observations of naked-eye stellar visibility. The number of visible stars decreased by an amount that can be explained by an increase in sky brightness of 7 to 10\% per year in the human visible band. This increase is faster than emissions changes indicated by satellite observations. We ascribe this difference to spectral changes in light emission and to the average angle of light emissions. Artificial lighting that escapes into the sky causes it to glow, preventing humans and animals from seeing the stars. Satellites can measure the light emitted upward, but they are not sensitive to all wavelengths produced by LED lighting or to light emitted horizontally. Kyba et al. used data from citizen scientists to measure how light pollution is affecting human views of the stars worldwide (see the Perspective by Falchi and Bará). Participants were shown maps of the sky at different levels of light pollution and asked which most closely matched their view. Trends in the data showed that the average night sky got brighter by 9.6\% per year from 2011 to 2022, which is equivalent to doubling the sky brightness every 8 years. —KTS Observations of the night sky by citizen scientists show that it is rapidly getting brighter due to light pollution.},
 }
+
+@article{andrae2015,
+  title    = {On Global Electricity Usage of Communication Technology: Trends to 2030},
+  author   = {Andrae, Anders S. G. and Edler, Tomas},
+  year     = {2015},
+  journal  = {Challenges},
+  volume   = {6},
+  number   = {1},
+  pages    = {117--157},
+  url      = {https://www.mdpi.com/2078-1547/6/1/117},
+  issn     = {2078-1547},
+  abstract = {This work presents an estimation of the global electricity usage that can be ascribed to Communication Technology (CT) between 2010 and 2030. The scope is three scenarios for use and production of consumer devices, communication networks and data centers. Three different scenarios, best, expected, and worst, are set up, which include annual numbers of sold devices, data traffic and electricity intensities/efficiencies. The most significant trend, regardless of scenario, is that the proportion of use-stage electricity by consumer devices will decrease and will be transferred to the networks and data centers. Still, it seems like wireless access networks will not be the main driver for electricity use. The analysis shows that for the worst-case scenario, CT could use as much as 51\% of global electricity in 2030. This will happen if not enough improvement in electricity efficiency of wireless access networks and fixed access networks/data centers is possible. However, until 2030, globally-generated renewable electricity is likely to exceed the electricity demand of all networks and data centers. Nevertheless, the present investigation suggests, for the worst-case scenario, that CT electricity usage could contribute up to 23\% of the globally released greenhouse gas emissions in 2030.},
+  doi      = {10.3390/challe6010117},
+}