Homewood has now turned his attention to the weather stations across much of the Arctic, between Canada (51 degrees W) and the heart of Siberia (87 degrees E). Again, in nearly every case, the same one-way adjustments have been made, to show warming up to 1 degree C or more higher than was indicated by the data that was actually recorded. This has surprised no one more than Traust Jonsson, who was long in charge of climate research for the Iceland met office (and with whom Homewood has been in touch). Jonsson was amazed to see how the new version completely “disappears” Iceland’s “sea ice years” around 1970, when a period of extreme cooling almost devastated his country’s economy.

One of the first examples of these “adjustments” was exposed in 2007 by the statistician Steve McIntyre, when he discovered a paper published in 1987 by James Hansen, the scientist (later turned fanatical climate activist) who for many years ran Giss. Hansen’s original graph showed temperatures in the Arctic as having been much higher around 1940 than at any time since. But as Homewood reveals in his blog post, “Temperature adjustments transform Arctic history”, Giss has turned this upside down. Arctic temperatures from that time have been lowered so much that that they are now dwarfed by those of the past 20 years.