$10 says
It will be inhabited by wookies or ewoks
Forget searching for radio-frequency signal patterns or exoplanetary megastructures. The new hotness in the search for extra-terrestrial intelligence is the detection of chlorofluorocarbons (CFCs), the ozone-eating greenhouse gasses formerly found in refrigerators and cans of hair spray. "Detecting alien 'hair spray' in the …
I'm looking at the global civilisation in the mirror...
I'm not sure if this counts as a "global warming story on The Register that isn't worth wearing out your eyeballs on the headline of", but, hey? hello? ozone layer?
(I've also forgotten whether CFCs and ozone respectively are supposed to be good or bad for climate change. You're certainly not supposed to do it deliberately.)
By the way, the last that I heard, the U.S. was thinking about not banning, or un-banning, some chemicals of this type. Now was it something about agricultural use... does that make any sense... well, on a scale of planetary species survival it doesn't, but for short term profit, maybe so.
"What "intelligent" lifeform releases planet destroying levels of chlorofluorocarbons anyway?"
??? CFC's are supposed to damage the ozone layer, they do not destroy planets. Why would you assume that some alien planet would even have an ozone layer?
The ozone layer merely prevents a lot of the local star's deadly radation from reaching the ground and exterminating all life. Or all life that doesn't have a thick black skin. Or dark green skin for plants that have to carry out photosynthesis to make a living in spite of the unobstructed death rays.
"but, hey? hello? ozone layer?"
Mars doesn't have an ozone layer. No evidence either way AFAIK on whether any discovered exoplanets do, so its not an issue. Of course the radiation it blocks could be an issue if humans wanted to make it home...
"last that I heard, the U.S. was thinking about not banning, or un-banning, some chemicals of this type."
Hadn't heard that myself, but it could be because China are largely ignoring those rules, and the US wants to stay competitive.
If we built a sufficiently powerful radio telescope on the far side of the moon, we may be able to pick up the "I Love Slartibartfast " show (2,837th repeat). That would work just as well as an indicator of alien civilisation, while at the same time providing some degree of entertainment. Perhaps.