Recently I chatted to my neighbor and we happened to stumble upon the topic of climate change. He told me: "I don't think the earth is really heating up, big changes don't happen so fast. This so-called warming effect is physically not plausible, even many scientists say so - I learnt about that when I followed the climate conference on YouTube." I was surprised about many aspects of this statement - that my neighbor, a well-educated man who reads medical journals for fun, is a climate change "ignorant" or "denier", that climate conferences are streamed on YouTube, and that denialist positions are supposedly spread there. ...