Published data were used to analyse the long-term annual temperature trends at eight locations located in the eastern region of Canada. Stations were located in the provinces of Ontario, Quebec, Newfoundland & Labrador, Prince Edward Island and Nova Scotia. (Sorry, but I could not find a station in New Brunswick!). Similarities in the trends for individual stations enabled a comprehensive trend to be established for the whole region.
The data used were all from the website of KNMI (the Royal Netherlands Meteorological Institute). Only raw data were used (ie as originally recorded, without any adjustments). Data were only used from stations located in rural areas or in small towns so as to avoid the possible influence of urbanisation on the temperatures.
The periods of the data ranged from 70 years to 122 years(the earliest record, at Yarmouth, commencing in 1871). Two stations, Cambridge Bay and Eureka, are located within the Arctic Circle.
The plots shown below are of the annual mean temperatures at each of the eight locations. On each plot a polynomial “best fit” trendline has been added. It should be noted that the trendlines near each extremity (ie near the start and end of the records) are quite sensitive to individual data points, whereas trendlines within the main body of the record are much more stable and reliable.
COMPARISON OF TRENDLINES
Annual Mean Temperature Trends
[ The basis of these trendlines can be seen from the analyses for the eight individual stations – see next section ]
Annual Mean Temperature Residual Trends
[ The individual trend-lines have been adjusted by constant amounts to be approximately zero at trend peaks around 1940-1960 ]
ANNUAL MEAN TEMPERATURE TRENDS FOR INDIVIDUAL STATIONS
Southampton (Ontario, Canada) 1873-1982
Moosonee (Ontario, Canada) 1877-2015
Inukjuak (Quebec, Canada) 1921-2015
Cartwright (Newfoundland & Labrador, Canada) 1934-2015
Natashquan (Quebec, Canada) 1914-1915
Gander (Newfoundland & Labrador, Canada) 1937-2015
Charlottetown (Prince Edward Island, Canada) 1872-2002
Yarmouth (Nova Scotia, Canada) 1871-2004
DISCUSSION AND COMMENTS
- The data analysed was limited to that which were available on the KNMI website.
- The annual mean temperature trend-lines for six of the eight stations are remarkably similar with the exception of Moosonee and Yarmouth.
- A well-defined cyclical pattern in the trend-line is apparent at six of the stations. A Low occurred in around 1980, and Highs occurred in around 1950 (but varied between 1940 and 1960) and 2010, indicating a cyclical wavelength of about 60 years.
- The ~2010 peak was generally about 0.5-1.0 deg C higher that that in ~1950.
- The ~1980 trough was generally about 0.8 deg C less than the peak in ~1950.
- Moosonee and Yarmouth did not show any trough around 1980 and did not show any definite peak around 2010.
- The consistency of the annual mean temperature trend-lines at six of the eight widely separated stations provides support for the good quality of the data and the conclusions drawn from the analysis. Moosonee and Yarmouth are outlier records (the reasons are unknown).
- There is no evidence of alarmingly increasing temperatures in recent years (except, perhaps, at Moosonee and Yarmouth). Conversely, there is strong evidence that a peak in the temperature cycle was reached in about 2010 and a decrease in the annual mean temperature of around 0.5 deg C could be anticipated to occur in the next 30-40 years.
This article was written by Brian Gunter of Narooma, NSW. In his previous life Brian was an engineering hydrologist involved over many years in the analysis of rainfall and river flow data for the planning of water resources projects in Australia, Asia and Africa. In recent years he has been one of the Marine Rescue NSW (previously Royal Volunteer Coastal Patrol) volunteer weather observers who operate the Narooma station for the Bureau of Meteorology.