Update: Depressingly, this wasn't funded by NASA at all, although one of the authors is from NASA's planetary science division (he worked on it in his free time). It's still a good read though. (Thanks, Kate Sheppard!)
Here's good news for people who have been trying to draft the tinfoil-hat crew into the fight against climate change: A genuinely not-at-all-made-up-by-me NASA not NASA study posits that global warming could alert extraterrestrial civilizations that humanity is getting too big for its britches, and prompt them to attack us.
The paper, which is mainly concerned with guessing whether aliens are mean or not, has a sobering theory about our climate:
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.
On the plus side, we are probably not going to be conquered by environmentalist aliens, or at least, they're not likely to eat us:
[I]f exponential growth is in fact unsustainable on the galactic scale … then we are much more likely to encounter a long-lived ETI civilization that follows a sustainable development pattern. Such a civilization may have no need to consume Earth systems (or humans) because they will have already found a way to effectively manage their resources over long timescales. Therefore, the possible unsustainability of long-term rapid expansion decreases the probability that ETI will destroy us.
It's tough to imagine that this paper is strictly serious — they reference, among other things, Star Trek and The Hitchhiker's Guide to the Galaxy ("where ETI place intrinsic value on civic infrastructure … and destroy Earth to make way for a hyperspace bypass"). But it's hella funny to watch taped-glasses NASA boffins theorize about whether aliens are jerks. And it gives you a completely genuine piece of scientific literature to point to when trying to convince your local basement-dwelling Robert Anton Wilson fan that climate change is a serious concept.
