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Rock star-scientist Brian Cox confused on more than global temperatures

By Jennifer Marohasy - posted Thursday, 18 August 2016


For example, I'm currently working on a 61-page expose of the situation at Rutherglen. Since November 1912, air temperatures have been measured at an agricultural research station near Rutherglen in northern Victoria, Australia. The data is of high quality, therefore, there is no scientific reason to apply adjustments in order to calculate temperature trends and extremes. Mean annual temperatures oscillate between 15.8°C and 13.4°C. The hottest years are 1914 and 2007; there is no overall warming-trend. The hottest summer was in 1938–1939 when Victoria experienced the Black Friday bushfire disaster. This 1938-39 summer was 3°C hotter than the average-maximum summer temperature at Rutherglen for the entire period: December 1912 to February 2016. Minimum annual temperatures also show significant inter-annual variability.

In short, this temperature data, like most of the temperature series from the 112 sites used to concoct the historical temperature record by the Australian Bureau of Meteorology does not accord with global warming theory.

So, adjustments are made by the Australian Bureau of Meteorology to these temperature series before they are incorporated into the Australian Climate Observations Reference Network – Surface Air Temperature (ACORN-SAT); and also the UK Met Office's HadCRUT dataset, which informs IPCC deliberations.

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The temperature spike in 1938-1939 is erroneously identified as a statistical error, and all temperatures before 1938 adjusted down by 0.62°C. The most significant change is to the temperature minima with all temperatures before 1974, and 1966, adjusted-down by 0.61°C and 0.72°C, respectively. For the year 1913, there is a 1.3°C difference between the annual raw minimum value as measured at Rutherglen and the remodelled value.

The net effect of the remodelling is to create statistically significant warming of 0.7 °C in the ACORN-SAT mean temperature series for Rutherglen, in general agreement with anthropogenic global warming theory.

NASA applies a very similar technique to the thousands of stations used to reproduce the chart that Cox held-up on Monday night during the Q&A program. I discussed these change back in 2014 with Gavin Schmidt, who oversees the production of these charts at NASA. I was specifically complaining about how they remodel the data for Amberley, a military base near where I live in Queensland.

Back in 2014, the un-adjusted mean annual maximum temperatures for Amberley – since recordings were first made in 1941 – show temperatures trending up from a low of about 25.5°Cin 1950 to a peak of almost 28.5°Cin 2002. The minimum temperature series for Amberley showed cooling from about 1970. Of course this does not accord with anthropogenic global warming theory. To quote Karl Braganza from the Bureau as published by online magazine The Conversation, "Patterns of temperature change that are uniquely associated with the enhanced greenhouse effect, and which have been observed in the real world include... Greater warming in winter compared with summer… Greater warming of night time temperatures than daytime temperatures".

The Bureau has "corrected" this inconvenient truth at Amberley by jumping-up the minimum temperatures twice through the homogenization process: once around 1980 and then around 1996 to achieve a combined temperature increase of over 1.5°C.

This is obviously a very large step-change, remembering that the entire temperature increase associated with global warming over the 20th century is generally considered to be in the order of 0.9°C.

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According to various peer-reviewed papers, and technical reports, homogenization as practiced in climate science is a technique that enables non-climatic factors to be eliminated from temperature series – by making various adjustments.

It is often done when there is a site change (for example from a post office to an airport), or equipment change (from a Glaisher Stand to a Stevenson screen). But at Amberley neither of these criteria can be applied. The temperatures have been recorded at the same well-maintained site within the perimeter of the air force base since 1941. Through the homogenization process the Bureau have changed what was a cooling trend in the minimum temperature of 1.0°Cper century, into a warming trend of 2.5°C per century.

Homogenization – the temperature adjusting done by the Bureau – has not resulted in some small change to the temperatures as measured at Amberley, but rather a change in the temperature trend from one of cooling to dramatic warming as was done to the series for Rutherglen.

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About the Author

Jennifer Marohasy is a senior fellow with the Institute for Public Affairs.

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