Could much of the global warming measured over recent decades be due to the changeover from traditional mercury thermometers to modern electronic thermometers? this articleprovides data that  shows that it is quite possible. This could explain why data that could prove this is being destroyed.

While I don’t believe in grand conspiracy theories, there is no doubt that there is a kind of "political correctness" that has enveloped much of the mainstream of society throughout the West regarding climate among other things (such as immigration, homosexuality etc.).  As far as climate is concerned it works  to keep the CO2 danger alive and to suppress evidence that could undermine it. Climate change, or global warming has become very political and for many it represents an opportunity to usher in a kind of world socialism in which the world becomes a "fairer place" as they see it. Others, of course see it as an opportunity to make money.