The reasoning behind 2010 being the 5th warmest year

In the annual UW Weather Station I had a hard time figuring out where the temperature ranked in the history of the region. The reason is that the records at the Waterloo-Wellington airport only go back to 1971 so to go back further we need to use a station in Kitchener that collected data from 1914 to 1977. Unfortunately between the stations there are going to be differences in equipment, personnel, and of course the location itself making comparison difficult.

When I did a straight ranking of annual temperatures from both stations the results looked like this:

1998 - 9.98
1949 - 8.64
1953 - 8.63
1931 - 8.63
1921 - 8.63
2006 - 8.44
1952 - 8.20
2001 - 8.14
1941 - 8.12
1955 - 8.07
1919 - 8.02
1975 - 7.96
1999 - 7.95
1991 - 7.88
2002 - 7.76

where the bolded number are from the Kitchener station. This would put the 2010 average
temperature of 7.90°C at 13th.

However as there are 7 years of overlap between the stations I was able to calculate that the Kitchener station was an average of 0.74 degree warmer than the Waterloo-Wellington airport station. This difference was very consistent for all 7 years.

So taking the Kitchener station numbers down by that amount make the ranking now look like this:

1998 - 9.98
2006 - 8.44
2001 - 8.14
1999 - 7.95
1949 - 7.90
1953 - 7.89
1931 - 7.89
1921 - 7.89
1991 - 7.88
2002 - 7.76
1952 - 7.46
1941 - 7.38
1955 - 7.33
1919 - 7.28
1975 - 7.22

So this puts 2010 as a tie for fifth overall.

To do a further check I looked for stations within 75 km of Waterloo that had long continuous records. Here are the four that I found:

Toronto airport (1938 - 2009) Missing 1939

1998 - 10.13
2006 - 9.70
2001 - 9.64
1999 - 9.46
2002 - 9.42
2005 - 9.02
2007 - 8.91
1991 - 8.88
1953 - 8.85
1949 - 8.73

London (1941-2001)

1998 - 9.88
2001 - 8.83
1953 - 8.83
1999 - 8.73
1987 - 8.73
1991 - 8.73
1949 - 8.68
1955 - 8.57
1990 - 8.47

Woodstock (1875-2006) Lots of missing years including 1953

1998 - 9.81
2001 - 8.97
1991 - 8.91
1990 - 8.69
1921 - 8.66
2006 - 8.65
1931 - 8.63
1999 - 8.55
2002 - 8.53

Fergus Shand Dam (1939-2006) Missing 1971

1998 - 8.74
2006 - 7.90
1999 - 7.79
2001 - 7.73
1991 - 7.55
2002 - 7.46
1990 - 7.43
1987 - 7.36
1949 - 7.25
2005 - 7.20
1953 - 7.10

Lots of numbers there, but what I was interested in seeing were not the absolute numbers, but the order of the years. It is pretty obvious that 1998 was by far the warmest in the region and the fact that at most of the stations, the same years that were in the top 5 in the Waterloo Region (1998, 2006, 2001, 1999, and 1991) were generally not only in the top at other stations but also higher than 1953 and 1949. All this increased my confidence that the order of the adjusted Waterloo Region data is reasonable.

This is the reasoning behind saying the 2010 was the 5th warmest year in the region since records began back in 1914.