Reykjavik Temperature Adjustments

By Paul Homewood

As we know, GHCN have been adjusting down historic temperatures across much of the Arctic, thus creating a false warming trend. It has been suggested by some that these adjustments may reflect station moves, Time of Observation Bias etc.

In Iceland, however, temperatures are already adjusted to take account of these factors. Trausti Jonsson, senior climatologist at the Iceland Met, has all the details up at his website Iceland Weather, where he says “Everyone can look up the numbers and compare both adjusted and earlier published values. Most of the later adjustments that have been made by the IMO are concerned with changes in the observing hours that necessitate slight adjustments.”

The effect of these adjustments can be seen by comparing temperatures at Reykjavik.

1925 1940 Actual original 4.37 5.15 Adjusted by Iceland Met 4.17 4.75

Which all raises the question, why do GHCN need to adjust at all? Surely the local met people know their temperature records much better?

The original temperature datasets are available here.

http://timarit.is/view_page_init.jsp?pubId=278&lang=is