Weather observatories in Australia, dating back 100 years or more, show cities getting hotter as they get bigger; but country towns have generally not been warming up. Some have actually been cooling down.
Most scientists recognise that temperature measurements in cities are influenced by non-climate things such as air-conditioners.
The cities in Australia also show the same trend as cities in the northern hemisphere with the rate of warming here being less 1°C per century.
So the countryside has not been warming up, whereas cities are getting hotter.
Substantial increases in carbon dioxide levels have been observed over this period, so if CO2 really was driving temperature upwards, we would expect a general rise in temperature in the bush and an even bigger rise in cities due to the combined effect of CO2 and non-climatic heating.
In many parts of the world, it’s hard to separate these two effects, so we are lucky here in Australia to have records from isolated country locations that are “un-contaminated” by the big city “heat island” effect.
The Australian Bureau of Meteorology (BOM) provides historical weather data on the internet (URL: www.bom.gov.au/climate/data/weather-data.shtml ).
The average of the peak temperatures for each month is available and this has been plotted in the attached graphs.
Graphs for the mean daily peak temperatures in January are shown for Echuca, Deniliquin and Bathurst – as examples of country sites.
The last graph is for Sydney and shows evidence of the “big city warming effect”.
In Deniliquin and Bathurst, there has actually been a fall in temperatures over the last 100 years; but in many other regional places there was just no trend, up or down.
E.M. Smith reports a similar pattern of “no warming” based on a large number of world-wide locations used by the Intergovernmental Panel on Climate Change (IPCC). (URL: http://chiefio.wordpress.com/2009/08/05/agw-is-a-thermometer-count-artifact/ ).
Graphs for additional Australian locations and additional months are available from the author. Dr A.L. McClintock can be contacted at sandy_at_mcclintock.tk.
Reprinted with permission from the web site of the Carbon Sense Coalition, www.carbon-sense.com. This web site has a great deal of valuable information on the role of carbon in life, energy and the atmosphere.