Ok this sounds like a reasonable strategy so how would one know what to look for in terms of signaling of this type of environment?  Basically they use this strategy:

Many exoplanet scientists turn to models to understand how Earth might appear if it were a distant alien world. However, the accuracy of these models can be difficult to gauge without observations to verify them.

That sounds like a good idea.  And why not look for exoplanets with this feature and maybe keep it in a certain distance for further evaluation as opposed to star systems that are billions of light years away.

And here is a video about one of the most interesting exoplanets that you may have heard about:

Exoplanet Kepler 452b with SETI Institute scientists Douglas Caldwell, Jeffrey Coughlin, Joseph Twicken. Hosted by Seth Shostak.

We hope you enjoy the video!

thanks to NASA for the great pic