The unchecked rise of greenhouse gasses could spell destruction for the human race — but not in the way you might expect. In a recently published paper, a NASA scientist speculates that rising levels of greenhouse gases in Earth's atmosphere could attract unwanted attention from intelligent extraterrestrial life.
The report, written by Shawn Domagal-Goldman — of NASA's Planetary Science Division — and academics from Penn State University, explores a broad range of extraterrestrial intelligence (ETI) contact scenarios and their varying consequences for humanity.
In one of these scenarios, "universalist" ETI (universalism in this case being comparable to our concept of environmentalism, only on a cosmic scale) notice changes in Earth's atmosphere. Upon observing humanity's rapid and destructive expansion on Earth, the ETI decide to intervene when they become concerned with our civilization's trajectory. The authors write:
Perhaps ETI believe that rapid expansion is threatening on a galactic scale. Rapidly (maximally) expansive civilizations may have a tendency to destroy other civilizations in the process, just as humanity has already destroyed many species on Earth. ETI that place intrinsic value on civilizations may ideally wish that our civilization changes its ways, so we can survive along with all the other civilizations. But if ETI doubt that our course can be changed, then they may seek to preemptively destroy our civilization in order to protect other civilizations from us. A preemptive strike would be particularly likely in the early phases of our expansion because a civilization may become increasingly difficult to destroy as it continues to expand. Humanity may just now be entering the period in which its rapid civilizational expansion could be detected by an ETI because our expansion is changing the composition of Earth's atmosphere (e.g. via greenhouse gas emissions), which therefore changes the spectral signature of Earth. While it is difficult to estimate the likelihood of this scenario, it should at a minimum give us pause as we evaluate our expansive tendencies.
The scenario is just one of many outlined in the report, which examines in creative and compelling detail how such encounters might benefit or harm humanity.
It's important to note that while one of the authors does have a NASA affiliation, this report is not actually sanctioned by NASA (which is a shame, because any official NASA report containing references to Hitchhiker's Guide to the Galaxy — which this report does — would almost definitely go down in history as one of science's greatest achievements ever) . Having said that, its in depth exploration of the implications of an ETI encounter is still a valuable one, and certainly makes for a thought provoking read.
You'll find the paper in its entirety (no subscription required) over at arXiv.org.