Published data were used to analyse the long-term annual temperature trends at five locations located in China and Mongolia. In China few suitable stations were available and these are all at inland locations, with none being near the coast or in the far west of the country. 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 86 years of complete annual data. The earliest record, at Tengchong, commenced in 1916.
The plots shown below are of the annual mean temperatures at each of the five 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 five 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 troughs around 1960-1980 ]
ANNUAL MEAN TEMPERATURE TRENDS FOR INDIVIDUAL STATIONS
Tengchong (China) 1916-2015
Xichang (China) 1926-2015
Jiuquan (China) 1934-2015
Dalanzadgad (Mongolia) 1936-2015
Choibalsan (Mongolia) 1936-2015
DISCUSSION AND COMMENTS
- The data analysed were limited to that which were available on the KNMI website.
- The annual mean temperature trend-lines for the five stations are similar.
- A well-defined cyclical pattern in the trend-line is apparent at all of the stations. A Low occurred in around 1960-1980 and Highs occurred around 1930-1940 and around 2010.
- The ~2010 “High” was generally about 1.5-2.0 deg C higher that that in ~1970.
- The ~1930 “High” was generally about 0.5-1.0 deg C higher that that in ~1970.
- The consistency of the annual mean temperature trend-lines of the five widely separated stations provides support for the good quality of the data and the conclusions drawn from the analysis.
- There is evidence of temperature rises of around 1.5-2.0 deg C since around 1970, but that a cyclical peak occurred around 2010.
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.