A recent report released by a handful of scientists was based on a "scenario analysis" of an alien invasion. In this scenario, it looks at the likelihood that aliens would "wipe out" the human race because of our hand in global warming... just as plausible a reason as any other, I suppose. After all, there have been a lot of alien invasion movies where the motive wasn't know, and now we can point to an easy culprit: climate change. In fact, it's the very fact our rapidly expanding populations that would incite the aliens to this carnage. It's remarkable, as Megan McArdle of Atlantic Monthly pointed out, "how often the aliens in science fiction just happen to be preoccupied with the exact same political issues that obsessed intellectuals of the era when the fiction was written."
Not really of course, because every issue (even interstellar ones) are framed within our own social and cultural perceptions. That said, the authors do make an interesting case for their scenario. According to the report, the authors see now as the crux of our civilization's expansion; a critical moment in which the changing composition of our atmosphere might act like a "beacon" to sentient alien species interested in our planet. Because we often study other planet's atmospheric compositions through the radiance of their light spectrums, alien species may be conducting those exact studies on our planet and, seeing the climate's composition changing very rapidly, may come to our weary planet's rescue.
One of the other variables in this scenario is our civilization's expansion. As we grow quickly (incredibly quickly, if you look at current population trends), we may be, "prone to destroy other life as they grow, just as humans have pushed species to extinction on Earth." Again, a pretty humanistic view, but hey, we're playing a game of hypotheticals here, right? Still, the authors envision that 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." Thus, aliens would attempt to wipe out our species before we were able to, say, achieve widespread space travel because we would become much more able to protect ourselves. I suppose that's plausible given he fact that private industry is now driving space travel in this country and one of the authors, Jonathan Adler, is connected to NASA who recently had to abandon their federally-funded manned-space travel programs. Perhaps this is the work of someone a little bitter at that fact?
Whatever the reasons for the so-called "study", it does make for some diverting reading, and it gives sci-fi lovers the world over one more motive to attach to all of those seemingly arbitrary alien-invasion films. Of course, Adler-and-Team aren't the first scientists to publicly wonder about a possible alien invasion. Famous physicist Stephen Hawking one paralleled a possible alien invasion to the European invasion of the American continent in the 15th and 16th centuries. I suppose, if I'm going to play the game, I have to acknowledge the fact that the best things we have to offer is an organism-rich planet. Should our species lose that bargaining chip, it might not play out well with out invaders.