Canada, Yellowknife  Region

This weeks review is completely different from the usual comparison of a UHI affected city station with surrounding rural stations.  The Yellowknife region is said to be the fastest warming area of Canada as measured by the CRU  Jones 1994, data.             The Karl 1998 paper in the IPCC book, "Regional Impacts of Climate Change", carries a map produced here as Figure 1, which shows warming anomalies from the Jones 1994 CRU dataset for five degree global grid boxes.  The two large red dots can be seen over NW  Canada mark the centres of five degree grid boxes warming at   ~ 2 degrees over the 1901-1996 period.

This review compares data from  three international climatology research groups and shows that, data from two actualy reveal cooling over the Yellowknife region, while only CRU and the Jones 1994 data claims to show this high degree of warming.

Figure 1   Global Grid Point Warming Anomalies using CRU Jones 1994 data, published in Karl 1998.

The data behind this high rate of warming  is examined in this review along with whatever other temperature datasets are available.
Only three  stations with any useful length of  recordings are avalable and these are are shown in Figure 2.

Figure 2   Station Positions Yellowknife Region.

Crosses on the map mark CRU stations and diamonds mark the GHCN series, many stations are in both datasets of course.  Note that The Hay River site is directly above the H in Hay.
For each labelled station three sets of data have been reviewed, these are;

Figures 3, 4 & 5 below compare all three sets of data for each site and Table A sets out the contrasting   temperature trends estimated from MS generated linear trendlines  shown on the graphs.  It is noteworthy that for all three stations the CRU trends register significantly more warming than the other two data sources.
Table A

Stations CRU Jones 1994 Version 2 GHCN adjusted GISS GHCN adjusted
Fort Smith ~ +2.7 degrees, 77 years ~ +1.75 degrees, 58 years ~ +0.85 degrees, 55 years
Yellowknife ~ +1.5 degrees, 50 years ~ -0.75 degrees, 50 years ~ -0.6 degrees, 50 years
Hay River ~ +1.8 degrees, 95 years ~ -0.8 degrees, 90 years ~ -0.4 degrees, 90 years

The  Fort Smith  data has been adjusted by GHCN and GISS from 1948 to 1970 which reduces the warming and also only CRU use the years prior to 1930. Presumably the GHCN compilers considered those data suspect.

Figure 3

Figure 4

Yellowknife has no data prior to the 1940's and once again GHCN and GISS have made  adjustments prior to 1970 and use early 1940's readings  which leave their data with slight cooling trends over the 50 years.

 The Hay River graph shows  GHCN and GISS found more complete data pre 1940 and also favour a warm adjustment in those years.  Both GHCN and GISS data cools slightly over the last century

Figure 5


There are many missing years in  all three stations, which reduces confidence in data.
It is interesting that in one of the higher warming areas for CRU grid boxes two other notable climate research teams disagree with the CRU trends.    All the above  leaves this high amplitude warming on a shaky foundation when two out of three international research teams actually find for a slight cooling over the century.

Because high latitude records tend to be riddled with data gaps and researchers  would have to suspect other homogeneity problems, the obvious way to resolving issues raised in this review would be to review trends further south in Canada, where there are more stations with better data quality.  Findings could then be extended further north from sounder foundations.

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Posted  16, July, 2000

2000 Warwick Hughes,