Is Moruya Getting Warmer?

Roy Lupton of Moruya asks: "Do your readers ever ask whether Moruya's weather is actually getting warmer? I have spent some time playing with the data supplied by the Bureau of Meteorology for the Moruya Pilot Station for the period 1910 - 2016 and have come up with the attached results. It would appear that Moruya is getting warmer but that milder winters are more evident that hotter summers."

The following graphs are obtained from the temperature data downloaded from the Bureau of Meteorology’s website http://www.bom.gov.au/climate/averages/tables/cw_069018.shtml. They refer to the MORUYA HEADS PILOT STATION.

The above graph shows 20 year rolling average temperatures. The actual data starts at 1910. Thedata shown for 1930 is the average maximum temperature for the period 1911 – 1930. The highvalue shown for 2016 is actually the average maximum temperature for the period 1997- 2016.

These are also 20 year rolling averages.

Once again 20 year rolling averages are used.

Comments. a) January and July temperatures. It seems obvious that both the January and July maximum temperatures are increasing. Over the past 100 years both the January and July maximum daily temperatures appear to have increased by about 1°C. An interesting question is why did the temperatures decrease in the 80s and 90s and is the more rapid increase since 2000 simply a return to the previous gradient or is it indicative of a more rapid increase? Both graphs seem to indicate that the increase only really started in the 60s. b) Hot Days and Cold Days. The number of hot days is increasing but only slowly whereas the number of cold days seems to be decreasing more rapidly. This seems counter to our perception. Perhaps we tend to judge statistics in the light of the present very hot summer that we are experiencing. I only used data until the end of 2016. c) Moruya Pilot Station. The temperatures at Moruya Pilot Station are not the same as the temperatures in Moruya. The summer temperatures are often considerably cooler due to the effect of the sea breeze and the winter temperatures can be warmer due to the moderating effect of the nearby ocean. d) Rolling Averages. The graphs in the first 3 sections make use of rolling averages. For example the year 2016 shows an average of 23.94. This does not mean that the average maximum for January 2016 is 23.94 but rather that the average for the years 1997 – 2016 is 23.94. The reason for using rolling averages is to try to smooth out some of the ups and downs.

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