" So, whether the aliens explore with chemistry or with radio waves, they might come to the same conclusion: a planet where there’s advanced technology must be populated with intelligent life-forms, who may occupy themselves discovering how the universe works and how to apply its laws for personal or public gain.

Looking more closely at Earth’s atmospheric fingerprints, human biomarkers will also include sulfuric, carbonic, and nitric acids, and other components of smog from the burning of fossil fuels. If the curious aliens happen to be socially, culturally, and technologically more advanced than we are, then they will surely interpret these biomarkers as convincing evidence for the absence of intelligent life on Earth. "

― Neil deGrasse Tyson , Astrophysics for People in a Hurry