I assume that general temperature profiles can be extracted through trees, Ice Cores, sediment cores? I would trust data collected and assessed from before 1980, only because perhaps there could be a bias trying to prove an agenda *after that date). Sorry for my cynicism. I am among the minority of conservatives that A. there is global warming, and B. it is attributed to greenhouse gas emissions. I could be wrong, since there is varying data, of which I am not an expert in. The graph/chart/depiction that we are all "discussing", in and by itself, can make an argument both ways.