Ozone holes in explanetary atmospheres

Searching for signs of an advanced civilization destroying themselves and their environment is a rather grim endeavour (e.g. Stevens et al. 2015), so we propose instead to search for evidence of extraterrestrial environmentalism. In this brief paper, we describe how given high enough photometric precision and a long time baseline, it would be possible to observe the creation and diminution of a hole in the ozone layer of an exo-Earth.

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By observing these systems across several decades, the actual number of environmental movements currently ongoing in the solar neighbourhood, ηGreen Earth, can be inferred. By replacing η⊕ in the Drake Equation with ηGreen Earth, this form of galactic anthropology allows us to recover not only the occurrence rate of advanced civilizations in the galaxy, but the occurrence rate of civilizations that we might actually want to contact.

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Thanks to Ian Czekala for reading a draft of this manuscript and providing valuable feedback. We also thank both Sarah’s Market and Cafe and Armando’s Pizza and Subs, both of Cambridage, MA, for the beer and sandwiches which enabled much of the work in preparing this manuscript. We would especially like to acknowledge the ozone layer on the Earth for shielding us from UV radiation throughout the preparation of this manuscript.

Also includes the first time I've ever seen someone give a citation for the spherical nature of the Earth.
http://arxiv.org/abs/1603.09428