Re: Green Communism
To be serious it's television that's more likely to tip off intelligent life and it's about now that we might expect a reply.
High power high frequency radio transmissions started in the 50's. That means that the broadcasts
might have been detected anywhere in a radius of 25 light years from us and been responded to.
It's quite possible radar transmissions might have been detected before the 50's and have been followed to their source.
But planetary global warming --- well nothing should ever be ruled out, just assigned degrees of probability eh!