The release of 2013 data by the BOM has provided me with plenty to work on. Various commentators are busily alarming people by claiming that the hottest year on record is an indication that global warming due to the enhanced greenhouse effect is already impacting Australia. What is most disappointing is that the BOM has done nothing to report the truth: that while Australia has definitely been warming, and breaking records, the data show no evidence of greenhouse warming.
One of the key indicators of warming uniquely associated with the enhanced greenhouse effect is night time temperatures (minima) increasing faster than daytime temperatures (maxima). The difference between the two is called the Diurnal Temperature Range, or DTR. So, decreasing DTR would be evidence of greenhouse warming.
Here is Australian DTR since 1947:
That’s dead flat or slightly rising for 67 years!
I couldn’t believe it either, and double checked. There’s no mistake- DTR shows no evidence of greenhouse warming in Australia, with a flat trend for 67 years.