>> The historical temperature data sets were not generated by a well designed sampling scheme. > I'm curious where this opinion comes from? ... my understandin

>> The historical temperature data sets were not generated by a well designed sampling scheme. > I'm curious where this opinion comes from? ... my understanding is the sampling takes a lot into account There is no sampling. We have an incomplete census of measured temperatures. Where humans decided to measure and record temperatures and which records survived were not determined by a sampling scheme. Even if the record were complete, it would be subject to selection biases. Just looking at the locations of temperature measurements in the definitive historical data set should drive this point home. Two, three, four hundred years ago, humans did not say "let's figure out a representative sampling scheme for accurately measuring global climate change." The current record is a function of where humans chose to live, work, produce, and travel.