Detecting advanced civilizations by their industrial pollution presents several challenges. The primary idea lies in discovering specific atmospheric signatures, such as industrial gases like chlorofluorocarbons (CFCs), that do not naturally occur and are indicative of technological activity. However, there are significant obstacles to this approach.
Firstly, the sensitivity required to detect such gases from interstellar distances with current technology is enormously high. While future advancements in telescope instrumentation, especially in infrared and spectroscopic capabilities, may increase our ability to identify such specific pollutants, the signal might still be exceedingly faint because the concentration levels of industrial pollutants could be much lower than naturally occurring atmospheric gases.
Moreover, distinguishing these signals from the immense background noise of cosmic phenomena requires not only advanced technology but also a clear understanding of the baseline atmospheric signatures of exoplanets. We currently have limited data on exoplanet atmospheres, and careful differentiation between natural and artificial markers is essential.
Additionally, just because a civilization is advanced does not necessarily mean it produces detectable levels of industrial pollution. A technologically advanced civilization may have developed clean technologies that leave little to no detectable atmospheric trace. They might be past the industrialization phase altogether, having adopted sustainable practices not discernible by pollution signatures.
In conclusion, while the concept remains intriguing and could offer insight into the technological activities of other civilizations, our current and near-future capabilities make the detection of industrial pollution as a method to discover advanced civilizations rather improbable.