GISS Double Up On Reykjavik Temperatures

By Paul Homewood

Before GHCN Adjustments

After GHCN Adjustments

We have already seen how GHCN have adjusted the temperatures for Reykjavik, given to them by the IMO ( Iceland Met Office). (Full story here.) By reducing historic temperatures up to 1965 by 0.8C, they have added an artificial warming trend that, according to the IMO, does not exist.

However, things actually get worse after GISS add their adjustments to the pot.

After GISS Adjustments

Up to 1972 GISS have knocked another 0.5C off the GHCN adjusted numbers, so there is now a total downward adjustment in historic temperatures of 1.3C. Let’s just recap why GISS apply their “homogeneity adjustments”. This is what they say:-

The goal of the homogenization effort is to avoid any impact (warming

or cooling) of the changing environment that some stations experienced

by changing the long term trend of any non-rural station to match the

long term trend of their rural neighbors, while retaining the short term

monthly and annual variations.

http://data.giss.nasa.gov/gistemp/sources_v3/gistemp.html

In other words, the UHI effect. Assuming that UHI is working to increase temperatures in urban areas over time, then the adjustment should be increasing past temperatures, and not reducing them. Of course, there may be local factors in Reykjavik that have operated to reverse the UHI effect, such as station relocation. However, the IMO confirm that there have been no significant relocations since 1945, or any other material changes.

If the GISS homogenisation is working as it should, there must be comparable rural stations nearby that show that a greater warming trend than Reykjavik’s. Yet we have already seen that this is not the case, for instance, this chart from the IMO:-

Figure 2. 7-year running means of temperature at three locations in Iceland, Reykjavík (red trace)), Stykkishólmur (blue trace) og Akureyri (green trace). Kuldakast = cold period. The first of the marked periods was the coldest one in the north (Akureyri), the second one was the coldest in Reykjavík

Finally. let’s take a look at the exact location of Reykjavik’s station, which is outside the Iceland Met’s HQ, (marked as A).

http://en.vedur.is/about-imo/office-hours-and-location/

As can be seen, it is in a fairly central position in Reykjavik, which has a population of about 120,000. (Greater Reykjavik is said to exceed 200,000). Wikipedia have this to say about the post war development there.

In the post-war years, the growth of Reykjavík accelerated. A mass exodus from the rural countryside began, largely due to improved technology in agriculture that reduced the need for manpower, and because of the population boom resulting from better living conditions in the country. A once primitive village was rapidly transformed into a modern city. Private cars became common and modern apartment complexes rose in the expanding suburbs. Much of Reykjavík lost its village feel.

Population has grown from about 6000 in 1900 and more than half of the buildings in the Reykjavik Metro area were erected after 1970,(see here).

It really is a nonsense to suggest that the Urban Heat Island effect has not been increasing, probably significantly so, in recent decades. If the GISS homogenisation system concludes that this effect has actually been declining, then there is something seriously wrong with their software.