Im pretty much annoyed by this term and its imho mis-use for many pseudo-experts. Experts for terrorism, amok, climate, babysitting... you probably all know this phenomenon of people designated in german TV interviews etc. as so-called experts.
So there are different levels when everyone of us starts to trust somebody. Appearance, Oratory,... but apart from these superficial wrong-leading criterions when can one/you call someone an expert?
Your answers will probably be coloured by different subjective criterions but actually i want to know if there are objective criterions when language-proofed institutions like TV stations/newspapers start calling one an expert, as it makes audience supposing alot of credibility. Is there a objective convention of speech. Often it looks to me like they nominate just one who was due to his journalistic career for long in touch we a specific topic. But thats not really expertise like doing a PHD. Even a PHD in physics is no expertise talking about climate physics, but you find many blogs-networks of self-acclaimed experts.
Has the internet and mass of information and necessary social interpretation of it eroded the Experte term? It already has to me a negative connotation like ideology and i personally dont know if you do someone a favour calling/introducing him publicly as expert.