Has SE Australia Warmed or Cooled over the last 100 years  ?
 Contrasting interpretations, GISS / NASA  vs Bureau of Meteorology

This page presents three  Australian State Capital temperature records compared to nearby rural or more rural neighbours.
This is a significant area for study because south eastern Australia has probably the best set of long term rural temperature records in the southern hemisphere.
GISS / NASA adjustments for urban warming  are presented in the case of  the State Capitals, contrasting with the Australian Bureau of Meteorology (BoM) adjustments.  BoM adjustments are also presented for the more rural stations.  The BoM adjustments are from the Torok and Nicholls paper, "A historical annual temperature dataset for Australia", Aust. Met. Mag. 45 (1996) 251-260.
For consistency,  all three graphs present the data  as follows;

Note that GISS does have adjusted data for centres over 9,000 population such as Newcastle and Mount Gambier but these are not used here.  They would make the comparisons even more marked.
Figure 1 shows  locations for Sydney, Melbourne and Adelaide with neighbouring stations.

Figure 2 shows Sydney - Newcastle comparisons and the striking difference in trends between GISS and the BoM is obvious.
While GISS adjusts Sydney for the gross urban heat island effect (UHI) and finds a trend very close to Newcastle.
The BoM authors adjust Newcastle and find a more warming trend similar to the their Sydney data.   The Newcastle station is at Nobbies Signal Station on a headland at the entrance to the Hunter River and  would be influenced to some extent by the UHI from this industrial city of 135,000 population.   Sydney's population is listed by GISS as 2.8 Million.
Figure 2

Figure 3 shows the contrasting data for Melbourne compared to Cape Otway, a lighthouse site.
GISS takes the approach of adjusting for Melbourne's very large UHI (2.58 Million population) and  finds a mild cooling trend.  The Cape Otway raw data probably  need a pre-1900 cooling adjustment but possible not as severe is that laid on by the BoM..
The BoM adjusts Cape Otway resulting in a slight warming trend similar to their adjusted Melbourne

Figure 3

Figure 4 shows comparisons between Adelaide and Mount Gambier. As in the previous cases  GISS adjusts Adelaide and find a cooling trend close to that for the near rural Mount Gambier.
The BoM adjusts Mount Gambier and produces a larger warming trend than the raw data for Adelaide.  Mount Gambier has a population of 18,000.
The BoM adjusted time series for Adelaide must be one of the few times temperature data from a city of this size (883,000 population) have been given a warming correction.
Research for the Torok and Nicholls paper was partly funded by the National Greenhouse Advisory Committee.

Figure 4

This review highlights a fascinating situation where two research groups produce radically different results from the same raw data.

One important question raised by this review is, "has south east Australia warmed or cooled since the late 19 C." ?

© Warwick Hughes, 2000
www.globalwarming-news.com
Posted 27, Sptember, 2000
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