In Canada, for example, the government even sent a leaflet out to every home in the country showing the conclusions of the graph: that current warming temperatures were historically unprecedented. That indicates how important, how influential this piece of research was. Indeed, it has been cited more than possibly any other paper in the field.
But then, in 2002/2003, a Canadian geologist called Stephen McIntyre came on to the scene. Having been a recipient of one of the Canadian government’s leaflets, he just thought the graph looked a bit, well, odd. So he went through the original research, and because of its rather dramatic shape showing steady temperatures for centuries and centuries and then a sudden lurch upwards in the twentieth century, McIntyre thought this just all seemed a bit dodgy.
This was partly due to McIntyre’s professional background in mining: in mining, the hockey-stick graph is a familiar phenomenon. It is a way for mining companies to encourage people to invest in them, so it probably set his alarm bells ringing.
Now McIntyre was to find two things wrong with Mann’s hockey-stick graph.
The rest here.